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SUMMARY1  INTRODUCTION1.1  General structure of grains1.2 Wheat1.3 Rice1.4 Maize1.5 Barley1.6 Oats1.7 Rye1.8 Millet1.9 Sorghum1.10 Triticale1.11 Other grains1.12 Key points2TECHNICAL ASPECTS OF CEREALS2.1 Cereal production2.2 Storage2.3 Processing2.4 Cereals and food safety2.5 Key points3THE ROLE OF CEREALS IN HEALTH AND DISEASE3.1 History of cereals in diet3.2 Nutritional value of cereals3.3 Contribution of cereals and cereal products in the diet3.4 Cereals in health and disease3.5 Labelling and health claims3.6 Consumer understanding3.7 Key points4FUTURE DEVELOPMENTS4.1 Fortification4.2 Genetic modification4.3 Gene–nutrient interactions4.4 Key points5CONCLUSIONS AND RECOMMENDATIONSREFERENCES GLOSSARYSummaryCereals are the edible seeds or grains of the grass family, Gramineae. A number of cereals are grown in different countries, including rye, oats, barley, maize, triticale, millet and sorghum. On a worldwide basis, wheat and rice are the most important crops, accounting for over 50% of the world's cereal production. All of the cereals share some structural similarities and consist of an embryo (or germ), which contains the genetic material for a new plant, and an endosperm, which is packed with starch grains.After harvest, correct storage of the grain is important to prevent mould spoilage, pest infestation and grain germination. If dry grains are held for only a few months, minimum nutritional changes will take place, but if the grains are held with a higher amount of moisture, the grain quality can deteriorate because of starch degradation by grain and microbial amylases (enzymes). Milling is the main process associated with cereals, although a range of other techniques are also used to produce a variety of products. Slightly different milling processes are used for the various grains, but the process can generally be described as grinding, sifting, separation and regrinding. The final nutrient content of a cereal after milling will depend on the extent to which the outer bran and aleurone layers are removed, as this is where the fibre, vitamins and minerals tend to be concentrated. There is potential for contamination of cereals and cereal products by pests, mycotoxins, rusts and smuts. Recently, acrylamide (described as a probable carcinogen) has been found in starchy baked foods. No link between acrylamide levels in food and cancer risk has been established and based on the evidence to date, the UK Food Standards Agency has advised the public not to change their diet or cooking methods. However, the Scientific Committee on Food of the European Union (EU) has endorsed recommendations made by Food and Agriculture Organisation/World Health Organization which include researching the possibility of reducing levels of acrylamide in food by changes in formulation and processing.Cereals have a long history of use by humans. Cereals are staple foods, and are important sources of nutrients in both developed and developing countries. Cereals and cereal products are an important source of energy, carbohydrate, protein and fibre, as well as containing a range of micronutrients such as vitamin E, some of the B vitamins, magnesium and zinc. In the UK, because of the mandatory fortification of some cereal products (e.g. white flour and therefore white bread) and the voluntary fortification of others (e.g. breakfast cereals), cereals also contribute significant amounts of calcium and iron. Cereals and cereal products may also contain a range of bioactive substances and there is growing interest in the potential health benefits these substances may provide. Further research is required in this area, including identification of other substances within cereals and their bioavailability.There is evidence to suggest that regular consumption of cereals, specifically wholegrains, may have a role in the prevention of chronic diseases such as coronary heart disease, diabetes and colorectal cancer. The exact mechanisms by which cereals convey beneficial effects on health are not clear. It is likely that a number of factors may be involved, e.g. their micronutrient content, their fibre content and/or their glycaemic index. As there may be a number of positive health effects associated with eating wholegrain cereals, encouraging their consumption seems a prudent public health approach. To increase consumption of wholegrain foods, it may be useful to have a quantitative recommendation. Additionally, a wider range of wholegrain foods that are quick and easy to prepare would help people increase their consumption of these foods. As cereal products currently contribute a considerable proportion of the sodium intake of the UK population, manufacturers need to continue to reduce the sodium content of foods such as breakfast cereals and breads where possible.Nutrition labelling is currently not mandatory in the UK, although many manufacturers provide information voluntarily. The fibre content of most UK foods is still measured using the Englyst method rather than the American Association of Analytical Chemists (AOAC) method used by other EU countries and the USA. However, UK recommendations for fibre intake currently relate to fibre measured by the Englyst method and not the AOAC method, and hence need revisions. EU changes to labelling regulations will see the labelling of common foods and ingredients causing allergic reactions, including cereals containing gluten and products derived from these foods. The introduction of EU legislation covering health claims may help consumers identify foods with proven health benefits.Several misconceptions exist among the public with regard to cereals and cereal products. Firstly, many more people believe they have a food intolerance or allergy to these foods than evidence would suggest and, secondly, cereals are seen by some as ‘fattening’. The public should not be encouraged to cut out whole food groups unnecessarily and, as cereals and cereal products provide a range of macro- and micronutrients and fibre, eliminating these foods without appropriate support and advice from a registered dietitian or other health professional could lead to problems in the long term.In the future it is possible that white flour in the UK may be fortified with folic acid (the synthetic form of the B vitamin folate) to decrease the incidence of neural tube defects during pregnancy. Such a move could also be of benefit for heart health, as poor folate status is associated with high homocysteine levels, an emerging risk factor for cardiovascular disease. However, high intakes of folic acid can mask vitamin B12 deficiency, a condition that occurs more frequently with age and has serious neurological symptoms affecting the peripheral nervous system.Manipulating the expression of native genes can increase the disease resistance of cereal crops. Novel genes may also be used for this purpose, as well as for developing cereals with resistance to herbicides, and cereals with improved nutritional properties (e.g. increased levels of iron in cereals and of beta-carotene in rice). The long-term consequences and consumer acceptability of such advances must be considered and consumer choice maintained. There is a continual growth in the knowledge of the interactions between human genes and nutrients, and in the future it may be possible to target specific nutrition messages to people with specific genetic profiles.
Content may be subject to copyright.
© 2004 British Nutrition Foundation
Nutrition Bulletin
,
29
, 111 –142
111
Blackwell Science, LtdOxford, UKNBUNutrition Bulletin1471-98272004 British Nutrition Foundation
? 2004
29
2111142
Briefing Paper
Nutritional aspects of cerealsBrigid McKevith
Correspondence:
Brigid McKevith, Nutrition Scientist, British Nutrition Foundation, High Holborn House, 52–54 High Holborn, London
WC1V 6RQ, UK.
E-mail: b.mckevith@nutrition.org.uk
BRIEFING PAPER
Nutritional aspects of cereals
Brigid McKevith
British Nutrition Foundation, London, UK
SUMMARY
1 INTRODUCTION
1.1 General structure of grains
1.2 Wheat
1.3 Rice
1.4 Maize
1.5 Barley
1.6 Oats
1.7 Rye
1.8 Millet
1.9 Sorghum
1.10 Triticale
1.11 Other grains
1.12 Key points
2TECHNICAL ASPECTS OF CEREALS
2.1 Cereal production
2.2 Storage
2.3 Processing
2.4 Cereals and food safety
2.5 Key points
3THE ROLE OF CEREALS IN HEALTH AND DISEASE
3.1 History of cereals in diet
3.2 Nutritional value of cereals
3.3 Contribution of cereals and cereal products in the diet
3.4 Cereals in health and disease
3.5 Labelling and health claims
3.6 Consumer understanding
3.7 Key points
4FUTURE DEVELOPMENTS
4.1 Fortification
4.2 Genetic modification
4.3 Gene–nutrient interactions
4.4 Key points
112
Brigid McKevith
© 2004 British Nutrition Foundation
Nutrition Bulletin
,
29
, 111 142
5CONCLUSIONS AND RECOMMENDATIONS
REFERENCES
GLOSSARY
Summary
Cereals are the edible seeds or grains of the grass family, Gramineae. A number of
cereals are grown in different countries, including rye, oats, barley, maize, triticale,
millet and sorghum. On a worldwide basis, wheat and rice are the most important
crops, accounting for over 50% of the world’s cereal production. All of the cereals
share some structural similarities and consist of an embryo (or germ), which con-
tains the genetic material for a new plant, and an endosperm, which is packed with
starch grains.
After harvest, correct storage of the grain is important to prevent mould spoilage,
pest infestation and grain germination. If dry grains are held for only a few months,
minimum nutritional changes will take place, but if the grains are held with a higher
amount of moisture, the grain quality can deteriorate because of starch degradation
by grain and microbial amylases (enzymes). Milling is the main process associated
with cereals, although a range of other techniques are also used to produce a variety
of products. Slightly different milling processes are used for the various grains, but
the process can generally be described as grinding, sifting, separation and regrind-
ing. The final nutrient content of a cereal after milling will depend on the extent to
which the outer bran and aleurone layers are removed, as this is where the fibre,
vitamins and minerals tend to be concentrated. There is potential for contamination
of cereals and cereal products by pests, mycotoxins, rusts and smuts. Recently, acry-
lamide (described as a probable carcinogen) has been found in starchy baked foods.
No link between acrylamide levels in food and cancer risk has been established and
based on the evidence to date, the UK Food Standards Agency has advised the pub-
lic not to change their diet or cooking methods. However, the Scientific Committee
on Food of the European Union (EU) has endorsed recommendations made by Food
and Agriculture Organisation/World Health Organization which include research-
ing the possibility of reducing levels of acrylamide in food by changes in formula-
tion and processing.
Cereals have a long history of use by humans. Cereals are staple foods, and are
important sources of nutrients in both developed and developing countries. Cereals
and cereal products are an important source of energy, carbohydrate, protein and
fibre, as well as containing a range of micronutrients such as vitamin E, some of the
B vitamins, magnesium and zinc. In the UK, because of the mandatory fortification
of some cereal products (
e.g.
white flour and therefore white bread) and the vol-
untary fortification of others (
e.g.
breakfast cereals), cereals also contribute signif-
icant amounts of calcium and iron. Cereals and cereal products may also contain a
range of bioactive substances and there is growing interest in the potential health
benefits these substances may provide. Further research is required in this area,
including identification of other substances within cereals and their bioavailability.
There is evidence to suggest that regular consumption of cereals, specifically
wholegrains, may have a role in the prevention of chronic diseases such as coronary
Nutritional aspects of cereals
113
© 2004 British Nutrition Foundation
Nutrition Bulletin
,
29
, 111 –142
heart disease, diabetes and colorectal cancer. The exact mechanisms by which cere-
als convey beneficial effects on health are not clear. It is likely that a number of fac-
tors may be involved,
e.g.
their micronutrient content, their fibre content and/or
their glycaemic index. As there may be a number of positive health effects associ-
ated with eating wholegrain cereals, encouraging their consumption seems a pru-
dent public health approach. To increase consumption of wholegrain foods, it may
be useful to have a quantitative recommendation. Additionally, a wider range of
wholegrain foods that are quick and easy to prepare would help people increase
their consumption of these foods. As cereal products currently contribute a con-
siderable proportion of the sodium intake of the UK population, manufacturers
need to continue to reduce the sodium content of foods such as breakfast cereals
and breads where possible.
Nutrition labelling is currently not mandatory in the UK, although many man-
ufacturers provide information voluntarily. The fibre content of most UK foods is
still measured using the Englyst method rather than the American Association of
Analytical Chemists (AOAC) method used by other EU countries and the USA.
However, UK recommendations for fibre intake currently relate to fibre measured
by the Englyst method and not the AOAC method, and hence need revisions. EU
changes to labelling regulations will see the labelling of common foods and ingre-
dients causing allergic reactions, including cereals containing gluten and products
derived from these foods. The introduction of EU legislation covering health claims
may help consumers identify foods with proven health benefits.
Several misconceptions exist among the public with regard to cereals and cereal
products. Firstly, many more people believe they have a food intolerance or allergy
to these foods than evidence would suggest and, secondly, cereals are seen by some
as ‘fattening’. The public should not be encouraged to cut out whole food groups
unnecessarily and, as cereals and cereal products provide a range of macro- and
micronutrients and fibre, eliminating these foods without appropriate support and
advice from a registered dietitian or other health professional could lead to prob-
lems in the long term.
In the future it is possible that white flour in the UK may be fortified with folic
acid (the synthetic form of the B vitamin folate) to decrease the incidence of neural
tube defects during pregnancy. Such a move could also be of benefit for heart health,
as poor folate status is associated with high homocysteine levels, an emerging risk
factor for cardiovascular disease. However, high intakes of folic acid can mask vita-
min B
12
deficiency, a condition that occurs more frequently with age and has serious
neurological symptoms affecting the peripheral nervous system.
Manipulating the expression of native genes can increase the disease resistance of
cereal crops. Novel genes may also be used for this purpose, as well as for developing
cereals with resistance to herbicides, and cereals with improved nutritional prop-
erties (
e.g.
increased levels of iron in cereals and of beta-carotene in rice). The long-
term consequences and consumer acceptability of such advances must be considered
and consumer choice maintained. There is a continual growth in the knowledge of
the interactions between human genes and nutrients, and in the future it may be pos-
sible to target specific nutrition messages to people with specific genetic profiles.
114
Brigid McKevith
© 2004 British Nutrition Foundation
Nutrition Bulletin
,
29
, 111 142
1 Introduction
Cereals can be defined as a grain or edible seed of the
grass family, Gramineae (see Fig. 1) (Bender & Bender
1999). Cereals are grown for their highly nutritious edi-
ble seeds, which are often referred to as grains. Some
cereals have been staple foods both directly for human
consumption and indirectly via livestock feed since the
beginning of civilisation (BNF 1994). Cereals are the
most important sources of food (FAO 2002), and cereal-
based foods are a major source of energy, protein, B
vitamins and minerals for the world population. Gener-
ally, cereals are cheap to produce, are easily stored and
transported, and do not deteriorate readily if kept dry.
1.1 General structure of grains (Fig. 2)
Grains develop from flowers or florets and, although the
structures of the various cereal grains are different, there
are some typical features. The
embryo
(or germ) is a
thin-walled structure, containing the new plant. It is sep-
arated by the
scutellum
(which is involved in mobilisa-
tion of food reserves of the grain during germination)
from the main part of the grain, the
endosperm
. The
endosperm consists of thin-walled cells, packed with
starch grains. If the cereal grain germinates, the seedling
uses the nutrients provided by the endosperm until the
development of green leaves that allow photosynthesis
to begin (FAO 1991; Kent & Evers 1994). The
endosperm is surrounded by the
aleurone
, consisting of
one or three cell layers (wheat, rye, oats, maize and sor-
ghum have one; rice and barley three). The outer layers
of the grain are the pericarp (derived from the ovary of
the flower) which surround the
seed coat
(the testa). The
outer thick-walled structures form the bran.
1.2 Wheat
Wheat is a major cereal crop in many parts of the world.
It belongs to the Triticum family, of which there are
many thousands of species (Kent & Evers 1994), with
T. aestivum
subspecies Vulgare and the hard wheat
T. durum
being the most important commercially (Mac-
rae
et al
. 1993). Wheat is grown as both a winter and a
spring cereal and, owing to the number of species and
varieties and their adaptability, it is grown in many
countries around the world. The great wheat-producing
countries of the world include the USA, China and
Russia; extensive wheat growing occurs in India,
Pakistan, the European Union (EU), Canada, Argentina
and Australia. It is estimated that 556.4 million tonnes
of wheat will have been produced in 2003, accounting
for 30% of the world’s cereal production (FAO 2003).
An ear or spike of grain is made up of spikelets (see
Fig. 3a). The wheat grain is enclosed between the lemma
and the palea of each spikelet (see Fig. 3b). The grain
may be elliptical, oval or ovate in shape and have short
or long brush hairs. Most cultivated varieties of wheat
have fusiform spikes, may be awned (bearded) or awn-
less, and are easily threshed.
Wheat is generally not classed by variety. Instead
classes are used, based on the time of year the wheat is
grown and the milling and baking quality of the flour
Figure 1
Taxonomy of the Gramineae family
(source: Shewry
et al.
1992).
Family: Gramineae
Subfamily
Tribe
Genus
Oryzeae Triticeae Aveneae Paniceae Andropogonee Cynodonteae
Eleusine
(Ragi)
SorghumPennisetum
(Millet)
Avena
(Oats)
Triticum
(Wheat)
Oryza
(Rice)
Secale
(Rye)
Zea
(Maize)
Coix
(Job's tears)
Hordeum
(Barley)
Figure 2
General structure of a grain (source:
Wheat: The Big Picture
(Dr
Gary Barker, webmaster. Gary.Barker@Bristol.ac.uk).
endosperm
aleurone layer
seed coat scutellum
embryo shoot
embryo root
brush
Nutritional aspects of cereals
115
© 2004 British Nutrition Foundation
Nutrition Bulletin
,
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, 111 –142
produced. Within each class there is a group of different
varieties of wheat with similar characteristics. Most of
the wheat produced is used for human consumption and
because of its unique properties, a large range of ingre-
dients and foods are produced, including wheat germ,
spelt (a coarse type of wheat), couscous, cracked wheat
or bulgur and wheat starch.
1.3 Rice
Rice is an important crop, forming a staple food for
many of the world’s population, especially those living
in Asia. Rice is produced mainly for use as human food,
including breakfast cereals, and in Japan it is also used
to brew saké (Kent & Evers 1994). There is a huge num-
ber of rice varieties (
~
100 000) but only a few are grown
widely (
e.g.
varieties of the improved semi-dwarf plant
type with erect leaves). Cereal production within the
European Union is shown in Table 2.
The rice grain consists of an outer protective coating
(referred to as the hull or husk) and the edible rice cary-
opsis. Brown rice consists of the outer layers of pericarp
(which contains pigment), seed coat, the embryo and the
endosperm (comprising the aleurone layer which
encloses the embryo, subaleurone layer and the starchy
or inner endosperm).
Wild rice is unrelated to rice. It is the grain of a North
American plant,
Zizania aquatica
, and, as it is difficult
to harvest, is more expensive than other grains. It has a
higher protein content than rice (Bender & Bender
1999).
1.4 Maize
Zea mays
L., also referred to as corn, originated in the
Western Hemisphere (Fast & Caldwell 2000). It is a
cheap form of starch and is a major energy source for
animal feed (Macrae
et al
. 1993). Although there are
hundreds of different varieties, the four main categories
of commercial importance are:
(1) dent maize (identified by the dent in the crown of
the kernel);
(2) flint maize (hard, round kernels);
(3) sweet corn (a dent-type maize);
(4) popcorn (flint-type maize which expands when
heated).
The maize kernel (the reproductive seed of the plant) has
four main parts – the germ, the endosperm, the pericarp
and the tip cap. Production in the USA exceeds that in
any other country (Fast & Caldwell 2000) and much
research has been done in the USA on the maize genome
(see section 4.2 for more on genetic modification).
Figure 3
(a) Ear of wheat (b) Wheat grain. (source: Wheat: The Big
Picture (Dr Gary Barker, webmaster. Gar y.Barker@Bristol.ac.uk).
(b)
rachis
spikelet 5
spikelet 3
spikelet 1
spikelet 2
spikelet 4
spikelet 6
peduncle
floret 4
floret 3
floret 1
floret 2
glume
rachilla
glume
palea
collar
(a)
lemma
lodicules
starnens
carpul
116
Brigid McKevith
© 2004 British Nutrition Foundation
Nutrition Bulletin
,
29
, 111 142
1.5 Barley
Barley is a resilient plant, tolerant of a range of condi-
tions, which may have been cultivated since 15 000
BC
(Fast & Caldwell 2000). Cultivated barley,
Hordeum
vulgare
, is mainly grown for animal feed, especially for
pigs, for malting and brewing in the manufacture of beer
and for distilling in whisky manufacture. A small
amount of barley is used for food. Pearled barley is eaten
in soups and stews in the UK and in the Far and Middle
East; barley is also used in bread (as flour) and ground
as porridge in some countries (Kent & Evers 1994).
The barley head or spike is made up of spikelets,
which are attached to the rachis in an alternating pat-
tern. The outer layers of the barley kernel consist of a
husk, completely covering the grain; the pericarp (to
which the husk is tightly joined in most species); the
testa or seed coat and the aleurone.
1.6 Oats
Oats can grow well on poor soil and in cool, moist cli-
mates and have mainly been grown for animal feed. A
small proportion is produced for human consumption –
oatmeal for porridge and oatcakes, rolled oats for por-
ridge, and oat flour for baby foods and for ready-to-eat
(RTE) breakfast cereals (Kent & Evers 1994). Oats are
also used in a range of non-food uses, including cosmet-
ics and adhesives (Macrae
et al
. 1993).
There are several different species, with the common
spring or white oat (
A. sativa
L
.
) being the most impor-
tant cultivated form.
A. byzantina
is a red-oat type
adapted to warmer climates where it is grown as a win-
ter oat. An oat spikelet consists of oat kernels. Each ker-
nel is enclosed by a hull (made up of two layers – a
lemma and palea) which is only loosely attached to the
groat. The groat, which makes up 65–85% of the oat
kernel, is enveloped by bran layers (pericarp, seed coat
and aleurone cells).
1.7 Rye
Rye is a hardy plant and is generally grown in cool tem-
perature zones, where other cereals can not be grown.
Rye can also grow at high altitudes and in semi-arid
areas. It is grown as a winter crop, being sown in early
autumn and harvested in early summer. The plant may
vary in height from 30 cm to more than 2 m. It is a
major crop in Russia, Poland, Germany and the Scan-
dinavian countries, where it is the major bread grain.
Rye is also used to produce crispbread and alcohol, and
it is used as animal feed (Kent & Evers 1994).
The grain is covered with a
glume
(husk), which is
normally bearded, and grains are arranged in an alter-
nating pattern along the rachis. The grain is thinner and
more elongated than wheat; it is normally greyish-
yellow in colour and varies in size from 1.5 mm to
3.5 mm. The grain consists of the starchy endosperm
(
~
86% of the grain), the pericarp and the testa (jointly
referred to as the bran and accounting for 10% of the
grain), with the remainder consisting of the germ (the
embryo and scutellum).
1.8 Millet
Millet refers to a number of different species, all of
which are small-grained, annual cereal grasses (Macrae
et al
. 1993; Bender & Bender 1999). The most impor-
tant type is pearl millet. A number of minor millets exist,
including finger (or ragi), proso and foxtail but as these
account for less than 1% of the grains produced for
human consumption, they are less important in terms of
world food production. However, these crops are
important in certain locations in Africa and Asia, where
major cereals can not be relied on to provide sustainable
yields (FAO 1995). Climatic and soil requirements,
length of growing period, grain consistency, size and
taste differ depending on the species.
Job’s tears (Coix lachryma-jobi) is a type of millet
wild grass, related to maize. It grows wild in parts of
Africa and Asia, where its seeds (adlay) are eaten
(Bender & Bender 1999).
1.9 Sorghum
Sorghum (
Sorghum bicolor
L. Moench) is a warm sea-
son crop, intolerant of low temperatures but fairly resis-
tant to serious pests and diseases. It is known by a
variety of names (such as great millet and guinea corn in
West Africa, kafir corn in South Africa, jowar in India
and kaoliang in China) and is a staple food in many
parts of Africa, Asia, and parts of the Middle East. Most
of the sorghum produced in North and Central Amer-
ica, South America and Oceania is used for animal feed
(FAO 1995).
The grain consists of a naked caryopsis, made up of a
pericarp, endosperm and germ. Although there is a huge
range of physical diversity, sorghums are classed into
one of four groups – (1) grain sorghum; (2) forage sor-
ghum; (3) grass sorghum; or (4) Sudan sorghums and
broomcorn (Macrae
et al
. 1993). Sorghums are grouped
using the following characteristics:
the colour of the pericarp (white, yellow or red);
presence/absence of pigmented testa (with/without
tannins);
Nutritional aspects of cereals
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Nutrition Bulletin
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, 111 –142
pericarp thickness;
endosperm colour (white, heteroyellow or yellow);
endosperm type (normal, heterowaxy or waxy).
1.10 Triticale
Triticale (full name Triticosecale) was the first cereal
produced by man by crossing wheat and rye. It has the
winter hardiness of rye and the baking properties of
wheat (Bender & Bender 1999). It is, however, suscep-
tible to diseases which attack wheat and rye (Macrae
et al
. 1993). Triticale is used mainly as a feed crop but it
can be milled into flour and used to make bread,
although adjustments are needed in recipe formulation
because it does not have the same gluten content as
wheat (Kent & Evers 1994).
1.11 Other grains
In addition to the cereals outlined above, there are sev-
eral others which, although not important on a global
level, may have an important role in certain parts of the
world. For example, buckwheat (also known as Saracen
corn) is produced from the plant
Fagopyrum esculentum
and is eaten as a cooked grain, porridge or baked into
pancakes. From the South American plant
Chenopo-
dium album
comes the grain quinoa, which is used in
Chile and Peru to make bread (Bender & Bender 1999).
1.12 Key points
There are many different types of cereals grown
worldwide, each sharing some structural similarities.
Cereals are the grain or edible seed of plants
belonging to the grass family and are very important
nutritionally.
Cereals consist of an embryo (or germ) which con-
tains the genetic material for a new plant. The main part
of the grain, is the endosperm, packed with starch
grains. If the cereal grain germinates, the seedling uses
the nutrients provided by the endosperm until the devel-
opment of green leaves.
2Technical aspects of cereals
Although various cereals are grown in different coun-
tries depending on climatic conditions, wheat and rice
are the most important cereals worldwide. Cereals are
grown for export as well as for domestic use and a num-
ber of different processes are used. These processes can
affect the nutritional and technical properties of the end
product.
2.1 Cereal production
Cereals are grown in a range of countries (Table 1). The
forecast for the world’s cereal production in 2003 is
1865 million tonnes, 30% as wheat and 21% as milled
rice. Over 50% of the world’s cereal is produced in
developing countries (FAO 2003).
The total UK 2003 cereal harvest was an estimated
22.3 million tonnes, with wheat and barley accounting
for about 66% and 30%, respectively, and oats account-
ing for about 3.5% of the total cereal production
(DEFRA & National Statistics 2003) (Table 2).
Ta b le 1
Forecasts for cereal production in 2003 (million tonnes)
Area Wheat Rice (paddy)
Coarse grains
(all other grains)
Asia 245.6 541.0 211.4
Africa 20.5 18.0 84.9
Central America 3.0 2.4 29.1
South America 22.0 19.5 76.0
North America 83.3 8.9 302.3
Europe 160.0 3.0 198.6
Oceania 22.0 0.4 10.4
World 556.4 396 912.8
Source: FAO 2003.
Ta b le 2
Useable cereal produced and human consumption of
cereals within the European Union for 2000/2001 (all figures are in
000 tonnes)
Country
Useable production
2000/2001
Human consumption
2000/2001
Belgium 2 246 1112
Denmark 9 412 595
Germany 45 219 8033
Greece Data not available Data not available
Spain 23 475 4110
France Data not available Data not available
Ireland 2 383 472
Italy 19 390 9822
Luxembourg 154 41
The Netherlands Data not available Data not available
Austria 4 498 849
Por tugal 1 484 1292
Finland 4 089 538
Sweden 5 669 841
The UK 23 991 7409
Source: Eurostat 2002.
118
Brigid McKevith
© 2004 British Nutrition Foundation
Nutrition Bulletin
,
29
, 111 142
2.2 Storage
After harvest, grains may either be temporarily stored on
the farm before being taken to a collection centre, or the
grains may go directly to a collecting centre. Grains are
then transported to larger storage facilities called coun-
try elevators, which are filled with grain by rolling belts.
Although methods for maintaining the quality of
cereal grains have been in practice since ancient times,
deterioration is seen even in countries with advanced
technology (Chelowski 1991). Storage is associated with
a range of hazards. Mould spoilage, pest infestations and
grain germination (which can occur if sufficient moisture
is present,
e.g.
condensation can be produced in metallic
bins) are the main problems (see section 2.4 about food
safety issues for further information on these topics).
Good storage is vital to minimise post-harvest losses and
although moisture content is the most important prop-
erty affecting stability of the grain during storage
(Chelowski 1991), temperature and duration of storage
are also important factors (Richard-Molard 2003).
An important step prior to storage is drying, to
remove excess water from the grain (Table 3). A range
of different types of driers may be used. High-tempera-
ture driers are capable of drying large quantities of grain
quickly but may also affect the grain if not used cor-
rectly,
e.g.
thermal denaturing of the cereal’s protein
may affect the properties of the final product. However,
this method has the advantage of destroying insects.
Natural drying methods have also been used,
e.g.
drying
corncobs using wind and solar driers. Cereals can also
be stored with higher water contents than usual in mod-
ified atmospheres, but this is only appropriate when the
end product is not required to have special properties
(
e.g.
to possess functional properties of bread). Exam-
ples of modified atmosphere storage include under-
ground storage and silos flushed with nitrogen. These
storage methods have the added advantage of killing
insects.
During storage there may be some nutritional changes
to the cereals, although for dry grains these changes will
be small even over a period of several months. If grains
are stored with a higher than ideal moisture content,
grain and microbial amylases may begin to breakdown
the starch, leading to a deterioration of grain quality
(Macrae
et al
. 1993). Unsaturated acids can be oxidised
to produce off-flavours and rancid odours (Macrae
et al
.
1993). There is little change in protein content, and
Jood & Kapoor (1994) found little change in the vita-
min content of wheat, maize and sorghum grains during
storage (up to 4 months) in insect-free conditions. Rice
may be aged for 3–4 months to improve the milling
yield and to make the milled rice expand more during
cooking (Macrae
et al
. 1993).
2.3 Processing
Cereals typically undergo a range of processes to pro-
duce a variety of different products, including non-food
products. Milling is the main process associated with
cereals, especially the bread cereals wheat and rye.
Slightly different milling techniques are used for the var-
ious cereals (see below) and a range of other processes
may also be used (
e.g.
extrusion and fermentation) in
the production of cereal products. As well as having
technical consequences, processing also changes the
nutritional content of cereals.
2.3.1 Milling
The process of milling can basically be described as
grinding, sifting, separation and regrinding. These steps
are repeated to extract a particular part of the grain, the
endosperm. Before milling begins, the cereal grains are
cleaned. Most modern equipment uses differences in
size, shape, colour, solubility, specific weight and
response to magnetic force to separate foreign material
from the grains. Prior to grinding, water may be added
to the cereal, which is allowed to rest before milling
(
tempering
). This allows absorption of water by the
grains, toughening the pericarp and germ so they do not
splinter during milling. If heat is also applied during
tempering (to mellow the endosperm and make it easier
to grind), then the process is referred to as
conditioning
(Hoseney 1994). To ensure production of a uniform
product, different grains may be blended prior to milling
and this is referred to as
gristing
(Fig. 4).
Ta b le 3
Codex standards for maximum moisture content (%) of
selected cereals
Grain
Maximum
moisture
content* Codex Alimentarius Standard†
Maize 15.5% Codex Standard 153-1995
Oats 14.0% Codex Standard 201-1995
Rice 15.5% Codex Standard 198-1995
Sorghum 14.5% Codex Standard 172-1989a
(Revision 1-1995)
Wheat 14.5% Codex Standard 199-1995
Durum wheat 14.5%
Whole and decorticated
pearl millet grains
13.0% Codex Standard 169-1989b
(Revision 1-1995)
*Lower moisture limits required for certain destinations in relation to climate,
duration of transpor t and storage.
Codex Alimentarius 1989a, 1989b,
1995a, 1995b, 1995c, 1995d.
Nutritional aspects of cereals
119
© 2004 British Nutrition Foundation
Nutrition Bulletin
,
29
, 111 –142
Figure 4 General stages of milling (reproduced with kind permission of National Association of British & Irish Millers (NABIM)).
120 Brigid McKevith
© 2004 British Nutrition Foundation Nutrition Bulletin, 29, 111 –142
In ancient times, milling was performed using stones
to crush the grain. Now grains are ground between two
rotating rollers. The first grinding stage through a
groove (referred to as breaking) opens the kernel and
scrapes off the endosperm. Then smooth ‘sizing’ and
‘reduction’ rollers decrease the endosperm granules to a
fine flour. After each stage of grinding, material is sent to
a sifting machine, where rotating sieves with differently
sized apertures separate particles of similar size. These
particles are then purified using air currents to separate
out endosperm and bran.
Milling rye Although this is similar to milling wheat, rye
is more prone to ergot (see section 2.4) so great care is
taken to remove this fungus during cleaning. Rye is also
tempered for a shorter period of time (6 h) because rye
kernels are softer than wheat kernels (Hoseney 1994).
Milling sorghum and millets These cereals are mainly
processed by traditional methods, using a hand-
operated wooden pestle and mortar. Generally the
grains are pounded and the husk removed by winnow-
ing or floatation. The grains are pounded further before
sieving (to remove coarse material which is pounded
again) to produce flour and meal.
Milling rice Whole (paddy) rice is dehulled by a rubber-
roll sheller to produce brown rice and coarse bran (from
the husk). Brown rice can be further processed to
remove the bran and produce white rice by pearling or
whitening, and polishing (Hoseney 1994).
Milling barley Barley is shelled and the husk removed
(via aspiration) before sifting and cutting. Barley may
then be pearled, with extensive pearling (removal of
over 50% of the original grain) producing pearl barley
and as a by-product, barley flour (Kent & Evers 1994).
Milling oats Two different systems have developed: the
traditional or dry-shelling system and the modern green-
shelling system. As can be seen from Table 4, they share
several similar steps (Kent & Evers 1994).
Milling corn Corn may be dry or wet milled. After tem-
pering, dry milling uses a degerminator (two cone-
shaped surfaces, one rotating inside the other) to remove
the hull and break the germ free from corn kernels. The
endosperm is then reduced to grits using roller milling,
similar to that used for wheat (Hoseney 1994). From this
a number of products are manufactured such as hominy
and polenta, the Italian porridge. Wet milling separates
corn into its four basic components – starch, germ, fibre
and protein. After steeping for 30–40 h, the next step in
the process involves a coarse grind to separate the germ
from the rest of the kernel. The remaining slurry is finely
ground and screened to separate the fibre from the starch
and protein. The starch is then separated from the
remaining slurry. The starch can then be converted to
syrup, or it can be made into several other products
including paper, paints, ethanol and laundry detergents.
2.3.2 Technical consequences of milling
During milling, several technological changes occur.
Firstly, there may be mechanical changes to the starch,
which can increase the level of enzyme activity. These
changes are important in bread making to provide
access for the alpha-amylase to work and so are not
intrinsically negative. The extent of this change will
depend on the quality of the grain and the parameters of
milling. Generally, the harder the grain, the greater the
extent of changes.
Secondly, there may be changes to the proteins within
the grains. During grinding, temperatures may reach
50–60C, which can denature the cereal’s proteins. This
can lead to a lower wet gluten yield, which decreases the
water absorption capacity of the flour. To prevent this,
excessive heating of the milled material is avoided.
After milling, flour is stored or aged. If this occurs
under normal atmospheric conditions, normal temper-
ature and normal humidity, it can beneficially affect the
quality of the flour. During ageing the flour will change
in colour from cream to white and it will develop better
baking properties (the gluten quality improves and its
extensibility decreases). Although ageing of wheat flour
may last up to 6 weeks, the major changes take place
within the first 10–12 days after milling. Rye flour ages
faster and so is aged for a shorter time (only about
2 weeks). Upon storage, rice undergoes ‘after-ripening’,
a series of biochemical changes which can influence
properties such as cooking time and stickiness (Kent &
Evers 1994).
Ta b le 4 Methods used to mill oats
Modern method Traditional method
Width grading
Shelling (by impact) Stabilisation (inactivation of enzymes)
Stabilisation Kiln drying
Kiln drying Length grading
Length grading Shelling (on stones)
Cutting
Grinding (for oatmeal, oat flour and bran)
Steaming and flaking (for rolled oats)
Nutritional aspects of cereals 121
© 2004 British Nutrition Foundation Nutrition Bulletin, 29, 111– 142
During milling there are risks of contamination from
metallic fragments, mineral dust (e.g. sand), pests,
microorganisms and heavy metals. However, controls
set nationally and internationally limit the extent to
which these contaminants can enter the food chain.
2.3.3 Nutritional consequences of milling
Fractionation of the grain during milling rather than the
milling process per se, is important from a nutrition per-
spective. As fibre, vitamins and minerals tend to be con-
centrated in the outer bran and aleurone layers of the
grain, the final nutrient content will depend on the
extent to which these layers are removed during pro-
cessing (MacEvilly 2003). Generally, the more processed
the grain, the lower the proportion of vitamins in the
final flour (Ottaway 1999). For example, white flour
may have less than one-third of the mineral and vitamin
content of wholegrains, although vitamins and minerals
are often added back after milling (see section 4.1). Mill-
ing may decrease some of the bioactive substances (phy-
tochemicals) that are found in cereals. For example,
Liukkonen et al. (2003) found the content of several
phytochemicals (e.g. lignans and phenolic acids)
decreased after milling. For more information on phy-
tochemicals, see section 3.2.4.
Starch and protein are less affected by processing as
these nutrients are concentrated in the endosperm of the
grain (Goldberg 2003). Milling, decortication, fermen-
tation and germination will increase protein digestibility
(due to the removal of fibre and enzymic breakdown of
proteins) but milling and decortication reduce the level
of lysine, the limiting amino acid in cereals (Macrae
et al. 1993). Refined grains also have a higher glycaemic
index (GI) than wholegrain products (Ludwig & Eckel
2002; see section 3.4 for more on GI). Some of the
grain’s lipids, which are mainly present in the germ and
bran, are distributed during milling into other fractions
(Southgate 1993).
2.3.4 Other processes
As well as milling, a range of other processes are used in
the production of cereals and cereal products. Generally,
the techniques used result in fragmentation of the food
matrix and gelatinisation of the starch granules. This
makes them readily digestible and generally they have
higher GI values. Cereal protein may be damaged during
some of the processes used to produce cereal products –
e.g. baking can lead to lysine loss (Southgate & Johnson
1993). Antioxidant activity (which is relatively high in
wholegrain cereal products) can be increased by brown-
ing reactions such as baking and toasting processes and
may be due to the formation of intermediate substances
from Maillard reactions with antioxidant activity
(Slavin 2003).
Many cereal-based foods undergo processing involv-
ing heat. This may affect the bioavailability of minerals
such as iron, calcium and zinc, e.g. availability may be
improved because of the hydrolysis of phytates by
phytase enzymes. Processes involving boiling may lead
to losses of around 40% for most B vitamins, although
losses of folate will be slightly higher. Losses during bak-
ing are generally lower, except for folate (MacEvilly
2003).
Recently, work in Sweden found baking starchy foods
such as rice and cereals could lead to the formation of a
substance called acrylamide. Acrylamide, which has
been described as a ‘probable carcinogen’, has been
found in a range of foods, including crisps, potato chips
and cereal products. No link between acrylamide levels
in food and cancer risk has been established and based
on the evidence to date, the UK Food Standards Agency
has advised the public not to change their diet or cook-
ing methods (Kelly 2003). However, the EU’s Scientific
Committee on Food has endorsed recommendations
made by Food and Agriculture Organisation (FAO)/
World Health Organization (WHO) in 2002 which
include researching the possibility of reducing levels of
acrylamide in food by changes in formulation and pro-
cessing (see http://europa.eu.int/comm/food/fs/sc/scf/
out131_en.pdf for more details).
Parboiling Rice is soaked in warm water (65C) for 4–
5 h before being steamed under pressure, dried and
milled. This process increases the total and head yield of
the rice and decreases the loss of nutrients during pro-
cessing (see below). Polishing rice removes the bran lay-
ers and the germ, leading to substantial losses in B
vitamins and a decrease in energy content [although the
energy available is higher in milled rice because it con-
tains less non-starch polysaccharides (NSP) on a weight
for weight basis]. Before polishing, unhusked rice may
be parboiled (steamed or boiled after soaking) to soften
the husk. During this process, some of the water-soluble
B vitamins located in the bran move into the endosperm,
along with some of the oil. Although cooking and par-
boiling rice reduces its protein digestibility by 10–15%,
there is a corresponding increase in the biological value,
leading to an unchanged net protein utilisation value
(Table 5).
Alkali processing The traditional method used to pro-
duce corn tortillas mixes maize with water and lime (cal-
122 Brigid McKevith
© 2004 British Nutrition Foundation Nutrition Bulletin, 29, 111 –142
cium hydroxide). After cooking, the mixture is steeped
overnight before being washed with fresh water to
remove the loosened pericarp and any residual alkali
(Macrae et al. 1993).
Fermentation Fermentation is used to produce a num-
ber of cereal products including bread, and alcoholic
beverages such as beer, vodka and whiskey. Examples of
fermented cereal foods include kenkey, made from a fer-
mented maize dough in Ghana and tapé ketan, a rice
dessert in Indonesia (Macrae et al. 1993). During bread
making, fermentation produces carbon dioxide making
the dough rise and increasing its volume. During the
proving stage, mechanically damaged starch grains are
broken down by amylase to produce maltose, which is
important for maintaining yeast activity (and therefore
gas production). In addition to yeast, lactic acid bacteria
are used in the production of sourdough bread to pro-
vide an acidic flavour to the final product. Some of the
bioactive substances in rye increase in sourdough bak-
ing (Liukkonen et al. 2003). The bacteria also affect the
dough proteins, making the dough stronger. In alcohol
production, fermentation produces ethanol and carbon
dioxide. In other fermented cereal products, the bio-
availability of minerals may be higher than in similar
non-fermented products due to the partial breakdown
of the phytate. Fermentation may also improve protein
quality because of bacterially produced lysine and by
improving protein digestibility (Macrae et al. 1993).
Extrusion The extrusion process uses a screw press with
a restricted opening to produce a shaped food product.
Extrusion cooking uses this process in addition to heat
(a high-temperature short-time procedure) to manufac-
ture a range of food products, including breakfast cereals
and pasta. Gualberto et al. (1997) found extrusion had
no effect on the insoluble fibre content of wheat bran but
observed decreased amounts in rice and oat brans. The
amount of soluble fibre increased in all three brans after
extrusion, except at the maximum screw speed (100%
maximum rotations per minute). The phytate content of
the three cereal brans was not affected by extrusion.
Sandberg et al. (1986) found that extrusion cooking
could impair the digestion of phytate in a high-fibre
cereal product owing to loss of phytase activity. No
effect was seen in absorption of iron and calcium but a
small decrease in the absorption of zinc, magnesium and
phosphorus led the authors to suggest that this could
have implications for foodstuffs consumed frequently
(Kivisto et al. 1986). In a more recent study, Fair-
weather-Tait et al. (1989) found extrusion cooking had
no effect on the retention of iron or zinc in adults.
Other processes In the production of breakfast cereals,
a number of other processes may be used (Fast & Cald-
well 2000). For example, flaked cereals can be made
from wholegrains or parts of the wholegrain or from
finer flour materials, with great pressures being used to
flatten the prepared material into flakes. Puffed cereals
are produced using either puffing guns (which are capa-
ble of holding very high temperature and high-pressure
steam) or an oven. Shredded cereals are produced by
passing the tempered grain between two rollers, one of
which is grooved and the other smooth. The grain is
squeezed into the grooves of the roller and emerges as
strands which are removed, accumulated in layers and
formed into biscuits or bite-sized pieces.
2.4 Cereals and food safety
Damage to cereals can occur in the field as well as after
harvesting. In addition to problems with pests, moulds
and fungi can contaminate cereals.
2.4.1 Pests
Infestation of cereal crops by pests can be a problem,
both before and after harvest. Insects (e.g. mites and
weevils) cause the most damage in stored cereals. Insects
can produce substances with unpleasant tastes and
smells (such as uric acid) and some transmit pathogenic
bacteria. They can also affect the cereal’s nutritional
value, for example, decrease the carbohydrate content
and increase free fatty acid levels (Chelowski 1991).
Jood & Kapoor (1994) found insects could affect the
vitamin content of cereals, decreasing the thiamin con-
tent by up to 69%, riboflavin content by up to 67% and
Ta b le 5 Comparison of selected nutrients in brown rice and white
rice (per 100 g)
Nutrient Brown rice, raw White rice (easy cook), raw
Energy (kcal/kJ) 357/1518 383/1630
Fat (g) 2.8 3.6
Protein (g) 6.7 7.3
Fibre (as NSP) (g) 1.9 0.4
Thiamin (mg) 0.59 0.41
Riboflavin (mg) 0.07 0.02
Niacin equivalents (mg) 6.8 5.8
Folate (mg) 49 20
NSP, non-starch polysaccharides.
Source: Food Standards Agency and Institute of Food Research 2002.
© Crown copyright material is reproduced with the permission of the
Controller of HMSO and Queen’s Printer for Scotland
Nutritional aspects of cereals 123
© 2004 British Nutrition Foundation Nutrition Bulletin, 29, 111– 142
niacin by up to 32%. When infestations are detected in
a silo or a ship, insecticides may be used, although the
type of insecticide and the level used are tightly con-
trolled (Macrae et al. 1993). Birds and rodents can also
contaminate stored cereals and cause food safety prob-
lems (Appert 1987).
2.4.2 Other contaminants
There is potential for contamination of cereals and
cereal products at many different stages, e.g. during
growth, harvest and storage. Mycotoxins are toxic
chemical substances produced by certain forms of
mould under specific conditions. A number of moulds
produce toxins (see Table 6). The most important myc-
otoxin with respect to cereals is produced by Aspergillus
flavus (Macrae et al. 1993). As mycotoxins are natural
contaminants of cereals, it is normal for small quantities
to appear in harvested cereals. Mycotoxins are only a
threat to human health if they are absorbed in large
quantities. A range of preventative strategies are used to
prevent the formation of mycotoxins before and after
harvest. Although mycotoxins are relatively stable, cer-
tain manufacturing processes can reduce their level, e.g.
milling of white flour removes deoxynivalenol which is
concentrated in the external layers of the bran (Quillien
2002).
Ergot is a fungus that can be found on a large number
of plants around the world (Lorenz 1979). Claviceps
purpurea, the ergot of medical importance, grows on
rye. Consumption of infected rye is harmful and can
lead to ergotism (also called Saint Anthony’s fire),
which produces gangrenous necrosis and hallucinations
(Macrae et al. 1993; Bender & Bender 1999). Ergot
rarely enters commercial food channels because of strict
grain standards but ergotism still occurs in animals from
time to time (Lorenz 1979).
Other problems that occur in cereals include rusts (a
fungal disease caused by species of Puccinia) and smut
diseases, which are caused by fungi which produce
masses of soot-like spores on the leaves, grains or ears.
2.5 Key points
•Wheat is the largest cultivated cereal crop, accounting
for 30% of the world’s cereal production. Rice is the
second most important crop on a world basis, account-
ing for 21% of the world’s cereal production.
Post-harvest, good grain storage is important to min-
imise losses, with moisture content a key factor.
Cereals undergo a range of processing, the most
common being milling, which affect their technological
and nutritional properties. Generally, the final nutrient
content of a cereal will depend on the extent to which
the outer bran and aleurone layers are removed dur-
ing processing, as this is where the fibre, vitamins and
minerals tend to be concentrated. Recently, acryla-
mide has been found in starchy baked foods. No link
between acrylamide levels in food and cancer risk has
been established and based on the evidence to date, the
UK Food Standards Agency has advised the public not
to change their diet or cooking methods (Kelly 2003).
However, the EU’s Scientific Committee on Food has
endorsed recommendations made by FAO/WHO
which include researching the possibility of reducing
levels of acrylamide in food by changes in formulation
and processing.
There is potential for contamination of cereals and
cereal products by pests, mycotoxins, rusts and smuts.
3The role of cereals in health and disease
Cereals have a long history of use by humans, dating
back to prehistoric times. Cereals are staple foods, with
current estimates of annual cereal consumption at
166 kg per capita in developing countries and 133 kg in
developed countries (FAO 2003). Cereals provide a
range of macro- and micronutrients and a high con-
sumption of cereals has been associated with a
decreased risk of developing several chronic diseases.
3.1 History of cereals in the diet
There is evidence to suggest that wild cereals were eaten
by human hunter-gatherers in ancient times (Toussaint-
Samat 1994). For example, sorghum has been used since
prehistoric times in Africa, Asia and Europe and prob-
ably originated in North Africa around 3000 BC (Kent
& Evers 1994). The origin of rice may be traced to a
plant grown in India at the same time, but it is first men-
tioned historically in China in 2800 BC. This is roughly
the same time maize was being grown in America. While
wild barley and wheat were grown in parts of the Mid-
dle East around 10 000 BC, these varieties produced
low yields because they were brittle and shed their seeds.
Ta b le 6 Examples of moulds producing mycotoxins in cereals
Mould Mycotoxin produced
Aspergillus flavus Aflatoxins B1 and B2
Penicillium verrucosum (temperate regions) Ochratoxin
Aspergillus ochraceus (tropical regions)
Fusarium species Fumonisins
Zearlenone
Deoxynivalenol
124 Brigid McKevith
© 2004 British Nutrition Foundation Nutrition Bulletin, 29, 111 –142
Due to natural mutations, more sturdy varieties devel-
oped and these were selected for cultivation and cereal
crops spread, reaching Britain sometime between 4000
and 2000 BC (Vaughan & Geissler 1997). Rye was
domesticated in Germany at about the same time (Kent
& Evers 1994).
Cereals were obviously an important part of our
ancestors’ lives, as cereals appear in a number of myths
and legends. For example, barley and wheat were
viewed as gifts from one of the gods, while the Aztecs
believed the same for corn (Toussaint-Samat 1994;
Werner 1997). Cereals play a pivotal role in a number of
different religions, including rice in the Japanese religion
of Shinto and bread in Christianity.
3.2 Nutritional value of cereals
Cereals are staple foods, providing a major source of
carbohydrate, protein, B vitamins and minerals for the
world’s population. As well as containing a range of
phytochemicals which may provide some of the health
benefits seen among populations consuming diets based
on plant foods (see Goldberg 2003), cereals also contain
a number of anti-nutrients.
3.2.1 Macronutrients
Carbohydrate Cereals are often classed as carbohy-
drate-rich foods, as they are composed of approximately
75% carbohydrate. Starches, the major component of
the cereal, occur in starch granules in the endosperm.
Starch granules differ in size (e.g. in rice they have a
diameter of only 5 mm, while in wheat they may be 25–
40 mm) and shape (either large, lens-shaped granules or
small, spherical granules). The ratio of amylose to amy-
lopectin within the starch granules varies, depending on
the cereal and its variety. Within common varieties of
cereals, 25–27% of starch is present as amylose, while in
waxy varieties (e.g. rice and corn) most of the starch is
amylopectin (see Fig. 5). However, in cereal products, a
proportion of this starch is not digested and absorbed in
the small intestine. This is referred to as resistant starch
and it appears to act in a similar way to dietary fibre.
Four categories of resistance have been defined
(Baghurst et al. 1996):
RS1 refers to starch that is physically inaccessible for
digestion as it is ‘trapped’ (e.g. intact wholegrains and
partially milled grains).
RS2 refers to native resistance starch granules (e.g.
found in high amylose maize starch).
RS3 refers to retrograded starch (e.g. found in cooked
and cooled potatoes, bread and some types of corn-
flakes).
RS4 refers to chemically modified starch (e.g. com-
mercially manufactured starches).
A small amount of free sugars is also present (~1–2%),
mainly as sucrose but low concentrations of maltose and
very low concentrations of fructose and glucose occur.
Protein Cereals contain about 6–15% protein (Gold-
berg 2003). The major storage proteins in wheat are gli-
adins and glutenins, while in rice it is glutelin (oryzenin),
in maize it is prolamin (zein); barley has hordeins and
glutelins, and in oats there are albumins and globulins
(Kulp & Ponte 2000). Although cereals provide a good
range of amino acids, the building blocks of proteins,
some are present in relatively low amounts. Essential
amino acids must be supplied by the diet, and from these
Figure 5 Approximate amylose and
amylopectin content of selected cereals.
0
25
50
75
100
Standard maize
Waxy maize
High amylose maize
Rice
Wheat
Cereal
Approximate content of starches (%)
Amylose
Amylopectin
Nutritional aspects of cereals 125
© 2004 British Nutrition Foundation Nutrition Bulletin, 29, 111– 142
the human body is able to make other (termed non-
essential) amino acids for itself (Table 7). The essential
amino acid that is in shortest supply in relation to need
is termed the limiting amino acid. For cereals the limit-
ing amino acid is lysine, except for rye, where tryp-
tophan is the first limiting amino acid (Macrae et al.
1993). More favourable essential amino acid composi-
tions can be found in rice, rye, barley and high-lysine
cultivars (e.g. maize, sorghum and barley) (Macrae et al.
1993). Combining cereals with other plant foods (e.g.
rice and beans) can compensate for these limiting amino
acids.
Lipids Although the germ is the richest source of lipids,
overall, lipids are only a minor component of cereals,
with the amount varying from a lipid content of 1–3%
in barley, rice, rye and wheat, to 5–9% in corn and
5–10% in oats, on a dry-matter basis (Southgate 1993).
This lipid fraction is rich in the essential fatty acid
linoleic acid (C18:2) (Table 8).
3.2.2 Micronutrients
Cereals can contribute to vitamin and mineral intake,
although the micronutrient content will depend on the
proportion of germ, bran and endosperm present (see
section 2.3). The pericarp, germ and aleurone layer are
rich in vitamins and minerals so refined cereal products
lose some of these nutrients, although in the UK
legislation requires the addition of thiamin, niacin,
calcium and iron to wheat flour (except wholemeal).
Such legislation currently varies between countries in
the EU.
Vitamins Cereals contain no vitamin C or vitamin B12,
no vitamin A and, apart from yellow corn, no beta-
carotene (Courdain 1999). However, cereals are an
important source of most B vitamins, especially thia-
min, riboflavin and niacin (Kulp & Ponte 2000). Cere-
als also contain appreciable amounts of vitamin E
(Table 9).
Ta b le 7 Essential amino acid composition of cereal grains
Amino acid
(g/ 100 g protein)
Wheat
(hard)
Rice Maize Barley Oats Rye Millet
(average of 7 types)
Sorghum
BMN HL N HL
Phenylalanine 4.6 5.2 5.2 4.8 4.3 5.2 5.4 5.0 5.5 5.1 4.9
Histidine 2.0 2.5 2.5 2.9 3.8 2.1 2.4 2.4 2.0 2.1 2.3
Isoleucine 3.0 4.1 4.5 3.6 3.4 3.6 4.2 3.7 3.8 4.1 3.9
Leucine 6.3 8.6 8.1 12.4 9.0 6.6 7.5 6.4 10.9 14.2 12.3
Lysine 2.3 4.1 3.9 2.7 4.3 3.5 4.2 3.5 2.7 2.1 3.0
Methionine 1.2 2.4 1.7 1.9 2.1 2.2 2.3 1.6 2.5 1.0 1.6
Threonine 2.4 4.0 3.7 3.9 3.9 3.2 3.3 3.1 3.7 3.3 3.3
Tr yptophan 2.4 1.4 1.3 0.5 0.9 1.5 - 0.8 1.3 1.0 0.9
Valine 3.6 5.8 6.7 4.9 5.6 5.0 5.8 4.9 5.5 5.4 5.1
B, brown; M, milled; N, normal; HL, high-lysine.
Source: Macrae et al. 1993.
Reprinted from Encyclopaedia of Food Science, Volume 2, Serna-Saldivar. ‘Dietar y importance (cereals)’, p. 787, © 1993, with permission from Elsevier.
Ta b le 8 Fatty acid profiles of selected cereals
Fat & fatty acids
(g/100 g food) Barley, pearl, raw
Oatmeal,
quick cook, raw Wheat flour, white Rye flour Rice, brown, raw Rice, white, raw
Total fat 1.7 9.2 1.2 2.0 2.8 3.6
Saturated fatty acids 0.29 1.61 0.16 0.27 0.74 0.85
Cis-monounsaturated fatty acids 0.14 3.34 0.13 0.21 0.66 0.91
Polyunsaturated fatty acids:
Total cis 0.77 3.71 0.51 0.95 0.98 1.29
n-6 (as 18:2) 0.70 3.52 0.48 0.82 0.94 1.26
n-3 0.07 0.19 0.03 0.13 0.04 0.03
Source: Ministry of Agriculture, Fisheries and Food 1998.
© Crown copyright material is reproduced with the permission of the Controller of HMSO and Queen’s Printer for Scotland
126 Brigid McKevith
© 2004 British Nutrition Foundation Nutrition Bulletin, 29, 111 –142
Minerals Cereals are low in sodium and are a good
source of potassium, in common with most plant foods.
Wholegrain cereals also contain considerable amounts
of iron, magnesium and zinc, as well as lower levels of
many trace elements, e.g. selenium. Rice contains the
highest level of selenium among the cereal grains, pro-
viding between 10 and 13 mg per 100 g (Table 10). The
selenium content of a cereal will vary depending on the
selenium content of the soil; for example, the selenium
content of wheat-grain can range from 0.001 mg per
100 g to 30 mg per 100 g (Lyons et al. 2003). Wheat
grown in North America generally has a higher sele-
nium content compared to that grown in Europe and
the switch to European wheat in recent years is sug-
gested as the main explanation of falling selenium
intake in the UK, although the effect (if any) of this
decrease on health is not currently known (Goldberg
2003).
3.2.3 Non-starch polysaccharides
All cereals are a rich source of NSP. There are two types
of NSP – insoluble and soluble – and, although both
may help with weight control (by delaying food leaving
the stomach), they have different effects in the body (see
section 3.3). The insoluble NSP content of most cereals
is similar, while the composition of the water-soluble
NSP varies. Arabinoxylans are the main water-soluble
NSP in wheat, rye and barley, while in oats it is the beta-
glucans. The amounts of beta-glucans and arabinoxy-
lans are higher in barley, oats and rye compared to
wheat (on a dry weight basis, 3–11%, 3–7%, 1–2% and
<1%, respectively) (Wood 1997).
3.2.4 Phytochemicals
Cereals contain a range of substances, which may have
health-promoting effects, that are often referred to as
Ta b le 9 Vitamin content of selected cereals (mg/per 100 g, unless specified)
Vitamin Vitamin E Thiamin Riboflavin Niacin equivalent (mg) Vitamin B6 (mg) Folate (mg)
Wheat flour, white, plain 0.30 0.31† 0.03 3.6† 0.15 22
Wheat flour, wholemeal 1.40 0.47 0.09 8.20 0.50 57
Rice, easy cook white, raw (0.10) 0.41 0.02 5.8 0.31 20
Rice, brown, raw 0.80 0.59 0.07 6.80 N 49
Popcorn, plain 11.03 0.18 0.11 1.7 0.20 3
Oatmeal, quick cook raw 1.50 0.90 0.09 3.4 0.33 60
Barley, pearl raw* 0.40 0.12 0.05 4.8 0.22 20
Rye flour, whole 1.60 0.40 0.22 2.6 0.35 78
Millet flour* Trace 0.68 0.19 2.8 N N
*From Holland et al. 1988. These values are for fortified flour.
N, the nutrient is present in significant quantities but there is no reliable information on the amount; (), estimated value.
Source: Food Standards Agency and Institute of Food Research 2002.
© Crown copyright material is reproduced with the permission of the Controller of HMSO and Queen’s Printer for Scotland
Ta b le 10 Mineral content of selected cereals (mg/per 100 g, unless specified)
Mineral Na (mg) K (mg) Ca (mg) Mg (mg) Fe (mg) Zn (mg) Se (mg)
Wheat flour, white, plain 3 150 140† 20 2.0† 0.6 2
Wheat flour, wholemeal 3 340 38 120 3.9 2.9 6
Rice, easy cook white, raw 4 150 51 32 0.5 1.8 13
Rice, brown, raw 3 250 10 110 1.4 1.8 10
Popcorn, plain 4 220 10 81 1.1 1.7 N
Oatmeal, quick cook raw 9 350 52 110 3.8 3.3 3
Barley, pearl raw* 3 270 20 65 3.0 2.1 (1)
Rye flour, whole (1) 410 32 92 2.7 3.0 N
Millet flour* 21 370 40 N N N N
*From Holland et al. 1988. These values are for fortified flour.
N, the nutrient is present in significant quantities but there is no reliable information on the amount; ( ), estimated value.
Source: Food Standards Agency and Institute of Food Research 2002.
© Crown copyright material is reproduced with the permission of the Controller of HMSO and Queen’s Printer for Scotland
Nutritional aspects of cereals 127
© 2004 British Nutrition Foundation Nutrition Bulletin, 29, 111– 142
phytochemicals or plant bioactive substances (see Gold-
berg 2003). Although flavonoids are only present in
cereals in small quantities, a number of other antioxi-
dants are present, including small amounts of tocot-
rienols, tocopherols and carotenoids. In laboratory
studies, wholegrain breakfast cereals have been found to
have an antioxidant content similar to fruits and vege-
tables (Miller et al. 2000) and one study suggests that
the major contributors of overall antioxidant activity
are bound phytochemicals (Adom & Li 2002). Lignans
are a type of phytoestrogen found in cereals, and
although the amount may be low (e.g. compared to that
in linseed), cereals may be an important source because
of the large quantities eaten daily.
3.2.5 Anti-nutrients
As previously mentioned, cereals contain relatively high
levels of phytate. On a dry weight basis, corn contains
0.89% phytate, soft wheat 1.13%, brown rice 0.89%,
barley 0.99% and oats 0.77% (Cheryan 1980). In most
cereals, the phytate is concentrated in the aleurone layer
and, to a lesser extent, the germ (Làsztity & Làsztity
1990). This means that milling affects the level of
phytate of most cereals, e.g. white flour has almost no
phytate remaining (Anon 1979). Phytate can bind min-
erals such as iron, calcium and zinc, and there is some
evidence showing decreased absorption of these miner-
als in the presence of phytate (e.g. McCance and
Widdowson observed a decreased absorption of calcium
in humans when phytate was added to white bread)
(Harris 1955). The extent to which this affects nutrient
status will depend on a number of factors, including the
amount of phytate hydrolysed during processing or the
amount that is digested in the gut; the concentration of
phytate and minerals in the food and the overall diet and
the nutrient status of the individual. This effect may be
of particular relevance to those people consuming a low-
calorie diet (Làsztity & Làsztity 1990).
Tannins, which are found for example in brown sor-
ghum, can bind and precipitate protein, decreasing its
digestibility. Germination and treatment of sorghum
with calcium oxide, potassium carbonate, ammonium
bicarbonate or sodium bicarbonate improves the nutri-
tional value of the grain. Pearl millet barley contains a
goitrogen (thioamide), found in the bran and
endosperm. Trypsin inhibitors, which can impair pro-
tein digestability, have also been isolated in pearl millet
and rye, although these are normally deactivated by
heating (Bender & Bender 1999). Rye also contains
other anti-nutrients, which have an impact in animal
nutrition but are of little concern to humans as they are
either removed during processing or destroyed during
baking.
3.3 Contribution of cereals and cereal products in
the diet
Cereal products play a central role in most countries and
are staple foods for much of the world’s population. In
the UK’s Balance of Good Health food model, cereals
and cereal products are grouped with bread and pota-
toes and this group of foods should form a main part of
meals (Fig. 6). The dietary guidelines accompanying the
Balance of Good Health encourage ‘plenty of foods rich
in starch and fibre’. Many of the foods in this group
could be described as wholegrain foods, although no
legal definition currently exists in the UK (although the
American definition of a minimum of 51% wholegrain
ingredient has been used by the Joint Health Claims Ini-
tiative). Currently America is the only nation to make
specific recommendations regarding wholegrain foods
(three servings a day) (Lang & Jebb 2003).
Table 11 shows the contribution that cereals and
cereal products (including bread, pasta, breakfast cere-
als, biscuits, cakes and pastries) make to the UK diet.
Cereals and cereal products are an important source of
Ta b le 11 Average contribution of cereals and cereal products to
the nutrient intake in the UK
Nutrient
% contribution of cereals to average intake of
nutrients
Boys* Girls* Adults†
Energy 35 33 31
Protein 27 26 23
Carbohydrate 45 42 45
Fat 22 21 19
Fibre (as NSP) 40 37 42
Thiamin 43 38 34
Riboflavin 34 31 24
Niacin 38 34 27
Folate 44 37 33
Vitamin B630 26 21
Vitamin D 37 35 21
Iron 55 51 44
Calcium 27 27 30
Sodium 40 38 35
Potassium 15 14 12
NSP, non-starch polysaccharides.
*Children National Diet and Nutrition Survey (NDNS) from Gregory et al.
2000. Adult NDNS data from Henderson et al. 2003a, 2003b.
© Crown copyright material is reproduced with the permission of the
Controller of HMSO and Queen’s Printer for Scotland
128 Brigid McKevith
© 2004 British Nutrition Foundation Nutrition Bulletin, 29, 111 –142
magnesium (providing 27% of the average adult
intake) and zinc (providing 25% of the average adult
intake) (Henderson et al. 2003b). It is also estimated
that about one-fifth of the UK’s selenium intake is from
cereals and cereal products (Goldberg 2003). Cereal
products also contribute a considerable proportion of
sodium, mainly from bread (15%, 14% and 14% for
boys, girls and adults, respectively). Although cereals
are naturally low in sodium, during production of
cereal products sodium is added. If manufacturers con-
tinue to reduce the sodium content of cereal products it
will help the population to reduce average total sodium
intake.
As can be seen from Table 11, cereals and cereal
products play an important role in the diet and are the
main source of many nutrients for both children and
adults. This is in part due to the mandatory fortifica-
tion of all wheat flour (apart from wholemeal) with
iron, calcium, thiamin and niacin, and the voluntary
fortification of breakfast cereals. This is demonstrated
by the 20% contribution fortified breakfast cereals
make to the average intake of iron in the UK adult
population.
3.3.1 Bread
Bread making goes back to prehistoric times, when a
mixture of grass seeds was ground into a crude form of
flour, to which water was added to form a dough
(Patient & Ainsworth 1994). Bread is made from four
ingredients – flour, water, yeast and salt and in the UK
most bread is produced using wheat flour, although
other flours, e.g. rye, are sometimes used. Different
types of bread are produced from wheat flour depending
on the proportion of the grain used, with brown breads
being made from flour of an intermediate extraction rate
(about 80–85%).
The traditional method of bread making involves the
mixing of the four ingredients to form a dough, which is
then kneaded to develop the gluten, before being left to
stand (during which time fermentation occurs). As this
method is quite time-consuming and labour-intensive, a
mechanical method, the Chorleywood process, was
developed which uses a mechanical mixer, a fast-acting
dough improver and a small amount of fat (Kent &
Evers 1994).
White bread may be the most commonly eaten food in
Figure 6 Balance of Good Health (British Nutrition Foundation version).
Nutritional aspects of cereals 129
© 2004 British Nutrition Foundation Nutrition Bulletin, 29, 111– 142
the UK; data from the recent adult National Diet and
Nutrition Survey (NDNS) indicated that 93% of men
and 89% of women ate it during the 7-day recording
period (Henderson et al. 2002). In the UK, weekly
household consumption of bread has decreased by
almost 1 kg since the 1940s. However, over the last
10 years there has been an increase in breads such as
French bread, naan bread, pitta bread and bagels
(DEFRA & National Statistics 2001). The current aver-
age adult intake of bread (including wholemeal, soft
grain and other bread) is about 91 g a day, roughly three
slices (Henderson et al. 2002).
The typical nutrient content of different breads is
given in Table 12. In terms of macronutrients, about
40% of bread is carbohydrate and 8–9% is protein; the
breads are all low in fat (less than 3 g of fat/100 g).
However, the fibre content is significantly higher in
wholemeal and brown bread than white bread.
3.3.2 Breakfast cereals
Developed in the late 19th century in America and
introduced to the UK in the early 20th century, RTE
breakfast cereals are an important source of nutrients.
For example, in a sample of schoolchildren in North-
ern Ireland, fortified RTE breakfast cereals were asso-
ciated with higher daily intakes of most micronutrients
and fibre, and with a macronutrient profile consistent
with current nutritional recommendations. Inadequate
intakes of riboflavin, niacin, folate and vitamin B12
(and iron in girls) were more likely in those children
not consuming fortified breakfast cereals (McNulty
et al. 1996). Although vitamin D is not usually associ-
ated with breakfast cereals, because of fortification of
RTE breakfast cereals, the recent NDNS report indi-
cated that they now account for 13% of the average
daily vitamin D intake in UK men and women (Hend-
erson et al. 2003b) (Fig. 7). Similarly, in children,
breakfast cereals account for 20% of the average daily
vitamin D intake in girls and 24% in boys (Gregory
et al. 2000).
Some recent work in schoolchildren has suggested
that breakfast cereals may help maintain mental per-
formance over the morning compared to no breakfast
or a glucose drink (Wesnes et al. 2003). A small study
in adults also found that a high-fibre carbohydrate-
rich breakfast was associated with the highest post-
breakfast alertness rating and the greatest alertness
between breakfast and lunch (Holt et al. 1999). A
larger study found an association between breakfast
cereal consumption and subjective reports of health,
with those adults who ate breakfast cereal every day
reporting better mental and physical health, com-
pared to those who consumed it less frequently (Smith
1999).
3.3.3 Pasta
Pasta is traditionally made from very hard (durum)
wheat, which is high in protein, and water. The mixture
is kneaded to produce a very stiff dough which is then
extruded, cut and dried. Pasta was bought to Britain in
the 18th century, and in 2000/2001 in Britain, among
those men and women who ate pasta (52% men and
53% of women), the mean consumption was 406 g and
Ta b le 12 Typical nutrient composition per 100 g of bread
Nutrient White Brown Wholemeal
Energy (kcal/kJ) 219/931 207/882 217/922
Protein (g) 7.9 7.9 9.4
Carbohydrate (g) 46.1 42.1 42
Total sugars (g) 3.4 3.4 2.8
Starch (g) 42.7 38.7 39.3
Fat (g) 1.6 2.0 2.5
Fibre (as NSP) (g) 1.9 3.5 5.0
Thiamin (mg) 0.24 0.22 0.25
Niacin equivalents (mg) 3.6 4.9 6.1
Folate (mg) 25 45 40
Iron (mg) 1.6 2.2 2.4
Calcium (mg) 177 186 106
NSP, non-starch polysaccharides.
Source: Food Standards Agency and Institute of Food Research 2002.
© Crown copyright material is reproduced with the permission of the
Controller of HMSO and Queen’s Printer for Scotland
Figure 7 Contribution of breakfast cereals to the mean vitamin and mineral
intake of UK adults (Henderson et al. 2003b).
© Crown copyright material is reproduced with the permission of the
Controller of HMSO and Queen’s Printer for Scotland
0
5
10
15
20
Thiamin
Riboflavin
Niacin equivalents
Vitamin B6
Vitamin D
Vitamin E
Iron
Calcium
Sodium
Magnesium
Sodium
Potassium
Zinc
Selected micronutrient
% contribution to mean intake in UK
adults
130 Brigid McKevith
© 2004 British Nutrition Foundation Nutrition Bulletin, 29, 111 –142
330 g a week, respectively (Henderson et al. 2002). The
nutrient content of white and wholemeal pasta is shown
in Table 13.
3.3.4 Biscuits, buns, cakes and pastries
Although cereal foods are generally low in fat, this sub-
group contributes 7% to the average daily intake of
total fat in adults and 5% in children (Gregory et al.
2000; Henderson et al. 2003a). Within the Balance of
Good Health, therefore, they do not fall into the same
category as the cereal products discussed above. Biscuits
and buns, cakes and pastries form part of the group of
foods containing fat; foods containing sugar.
3.3.5 Other foods containing cereals
Cereals and cereal products are used in a wide range of
other foods. Cereal-based porridges are traditionally
used as weaning foods in many parts of the world and
within the UK baby cereals are often used at the first
stage of weaning.
3.4 Cereals in health and disease
There is much interest in understanding the role of par-
ticular foods, such as cereals, in the diet and their effect
on health. Some of the work on cereals has focused spe-
cifically on wholegrain cereals and work suggests that
people who eat wholegrains may have better nutrient
intake profiles. For example, people in the USA who ate
wholegrains had higher intakes of vitamins and miner-
als, and lower intakes of total fat, saturates and added
sugars compared to those who did not eat wholegrains
(Cleaveland et al. 2000). Cereals may also have a range
of health benefits as discussed below.
3.4.1 Energy balance
Cereal foods have a relatively low energy density, and
foods rich in wholegrain cereals may help reduce hunger
as they are relatively bulky (Holt et al. 1999; Saltzman
et al. 2001). Cereals may also affect body weight regu-
lation through effects on hormonal factors (Koh-Baner-
jee & Rimm 2003). By focusing on increasing cereal
intake, it is possible to achieve a reduction in consump-
tion of other foods and a reduction in fat intake. For
example, a small study using free-living subjects found
that including 60 g of breakfast cereal with semi-
skimmed milk every day decreased the average intake of
energy from fat by 5.4%, with a similar increase in
energy contribution from carbohydrate (Kirk et al.
1997). In another small study, 14 subjects consumed
four different breakfasts of the same energy content but
with differing macronutrient content – two fat-rich and
two carbohydrate-rich (low or high fibre). The high-
fibre, carbohydrate-rich breakfast was the most filling
meal and was associated with less food intake during the
morning and at lunch. Hunger returned at a slower rate
after this meal than after the low-fibre, carbohydrate-
rich meal. Both fat-rich breakfasts were more palatable
but less satiating than the carbohydrate-rich meals (Holt
et al. 1999). The recent WHO/FAO expert committee
report on nutrition and chronic diseases suggested that a
high intake of NSP may be a protective factor against
overweight and obesity (WHO/FAO 2003).
3.4.2 Glycaemic index (GI)
The GI is used for classifying carbohydrate-containing
foods. It can be defined as ‘the incremental area under
the blood glucose curve after consumption of 50 g car-
bohydrate from a test food, divided by the area under
the curve after eating a similar amount of control food
(generally white bread or glucose)’ (Ludwig & Eckel
2002). The glycaemic load (GL) assesses the total gly-
caemic effect of the diet and is the product of dietary GI
and total amount of dietary carbohydrate (Jenkins et al.
2002). The rate of digestion and absorption of carbo-
hydrates is influenced by a range of factors (Pi-Sunyer
2002), including:
the nature of the monosaccharide components;
the nature of the starch (e.g. the amylose to amylopec-
tin ratio);
Ta b le 13 Nutrient content of white and wholemeal pasta (per
100 g)
Nutrient White (boiled) Wholemeal (boiled)
Energy (kcal/kJ) 104/442 113/485
Protein (g) 3.6 4.7
Carbohydrate (g) 22.2 23.2
Total sugars (g) 0.5 1.3
Starch (g) 21.7 21.9
Fat (g) 0.7 0.9
Fibre (as NSP) (g) 1.2 3.5
Thiamin (mg) 0.01 0.02
Niacin equivalents (mg) 1.2 2.3
Iron (mg) 0.5 1.4
Calcium (mg) 7 11
Source: Food Standards Agency and Institute of Food Research 2002.
© Crown copyright material is reproduced with the permission of the
Controller of HMSO and Queen’s Printer for Scotland
Nutritional aspects of cereals 131
© 2004 British Nutrition Foundation Nutrition Bulletin, 29, 111– 142
cooking or food processing; (e.g. milling increases the
GI of cereals);
other food components (e.g. fat, protein and fibre).
Several metabolic effects may be related to the
reduced rate of glucose absorption after a low-GI food,
e.g. a lower blood glucose concentration and a reduced
post-prandial rise in gut hormones and insulin, main-
taining suppression of free fatty acids. The GI concept
suggests a possible role for the rate of carbohydrate
digestion in the prevention and treatment of chronic dis-
ease. There may also be a role for low-GI foods in
weight management, as they promote satiety. Although
one study observed that a similar amount of weight loss
occurred with a high-GI diet as with a low-GI diet
(Wolever et al. 1992), several intervention studies have
found that energy-restricted diets based on low-GI foods
produce greater weight loss than those based on high-GI
foods (Brand-Miller et al. 2002). A systematic review
highlighted inconsistent results in short-term studies
measuring appetite sensations following low GI vs.
high-GI foods. In terms of weight loss, the 20 longer-
term intervention studies found no advantage in using a
low-GI diet compared to a high-GI diet (1.5 kg loss on
a low-GI diet vs. 1.6 kg on a high-GI diet) (Raben
2002). Several epidemiological studies have also discov-
ered a relationship between a high-GI diet and chronic
disease, e.g. coronary heart disease (CHD – see section
on heart health), type 2 diabetes (see section on diabe-
tes) and cancer (Jenkins et al. 2002).
A high-fibre wheat or high-fibre rye diet has been
shown to decrease post-prandial plasma insulin by 46–
49% and post-prandial plasma glucose by 16–19% in
overweight, middle-aged men compared to a low-fibre
diet but it is unclear if subjects were healthy, or had
impaired glucose tolerance or type 2 diabetes (McIntosh
et al. 2003). Although the authors suggested more com-
prehensive testing should be undertaken, they concluded
that it was promising that even in the short term,
wholegrain foods were capable of decreasing the glycae-
mic response.
The recent WHO/FAO report on nutrition and
chronic disease associated low-GI foods with an overall
improvement in glycaemic control in people with diabe-
tes, and several countries educate people with diabetes
about GI. The WHO/FAO report also listed low-GI
foods as a possible factor in decreasing the risk of devel-
oping type 2 diabetes and reducing the risk of weight
gain (WHO/FAO 2003).
3.4.3 Heart health
Several large cohort studies in America, Finland and
Norway have found that people eating relatively large
amounts of wholegrain cereals have significantly lower
rates of CHD and stroke. A recent review by Hu (2003)
identified several prospective cohort studies showing an
inverse association between wholegrain consumption
and risk of cardiovascular disease (CVD) (Table 14). In
addition, the prospective Physicians’ Health Study in the
USA following ~86 000 men for over 5 years found men
in the highest category for wholegrain breakfast cereal
intake ( 1 serving/day) had a 20% decreased risk of
dying from CVD, compared to those in the lowest cat-
egory [relative risk (RR) of 0.80] (Liu et al. 2003). No
significant associations between total or refined break-
fast cereal intakes and CVD mortality were found.
One way wholegrain cereals may be having an effect
on heart health is the effect of soluble fibre on choles-
terol levels. A meta-analysis of 67 controlled studies
found soluble fibre (2–10 g/day) was associated with
small but significant reductions in total cholesterol and
low density lipoprotein cholesterol (LDL-C) concentra-
tions. No significant difference was seen between solu-
ble fibre from oat, psyllium or pectin. There was,
however, substantial heterogeneity between studies, sug-
gesting the effects of fibre are not uniform. Although in
practical terms, such an effect would be modest (e.g. 3 g
of soluble oat fibre could decrease total and LDL-C con-
centrations by ~0.13 mmol/L), there is a US-approved
health claim for soluble fibre and the risk of CHD (see
Ta b le 14 Wholegrain cereal consumption and decreased risk: prospective cohort studies reviewed by Hu (2003)
Condition Subjects
Decreased risk
(adjusted RR) Reference
Stroke 75 521 women 36% (0.64) Liu et al. 2000
CHD 75 521 women 25% (0.75) Liu et al. 1999
Fatal CHD 34 492 women 30% (0.70) Jacobs et al. 1998
Non-fatal heart attack 31 208 men & women 44% (0.56) Fraser et al. 1992
CHD 31 208 men & women 11% (0.89) Fraser et al. 1992
RR, relative risk; CHD, coronar y heart disease.
132 Brigid McKevith
© 2004 British Nutrition Foundation Nutrition Bulletin, 29, 111 –142
section 3.5 for more on health claims) (Brown et al.
1999). As well as encouraging consumption of foods
rich in soluble fibre, there may be scope for increasing
the soluble fibre content of cereal products. In the only
randomised controlled trial (RCT) using men with a his-
tory of myocardial infarction (the Diet and Reinfarction
Trial study), advice to increase cereal fibre had no effect
on CHD or all-cause mortality (Ness et al. 2002), but
further work in healthy individuals is warranted.
Another area of interest is the influence of GI on
blood lipids. Two observational studies have shown a
negative relationship between GI and high density lipo-
protein cholesterol (HDL-C) concentrations, suggesting
a low-GI diet may preserve HDL-C levels (Jenkins et al.
2002). Several RCTs have shown that, in people with
diabetes, diets containing a large proportion of the
dietary carbohydrate as low-GI foods have shown
improved blood lipids, independent of dietary fibre
intake (Mann 2001).
There may currently be insufficient evidence to dem-
onstrate a cause and effect between heart health and
wholegrain foods, but the WHO/FAO stated that there
was a ‘probable’ level of evidence demonstrating NSP
and wholegrain cereals decrease the risk of CVD
(WHO/FAO 2003). Several health claims in the area of
heart health and wholegrain cereals have been approved
(see section 3.5).
3.4.4 Diabetes
Prevention of diabetes A potential role for fibre in the
prevention of diabetes was put forward over 30 years
ago, and a high intake of cereal fibre has consistently
been associated with a lower risk of diabetes (Willett
et al. 2002). For example, in a large prospective study of
more than 42 000 men followed for about 12 years, an
inverse association was found between wholegrain
intake and type 2 diabetes. After adjustment for con-
founding factors, men in the highest quintile of intake
compared to those in the lowest had an RR of 0.58
(Fung et al. 2002). Similar results have been seen in
women (e.g. Liu et al. 2000; Meyer et al. 2000). Mon-
tonen et al. (2003) studied the intake of wholegrain and
fibre of over 4 000 Finnish men and women, and the
subsequent incidence of type 2 diabetes during a 10-year
follow-up. An inverse association was found between
wholegrain intake and risk of type 2 diabetes, with an
RR between the highest and lowest quartiles of
wholegrain consumption of 0.65, i.e. a 42% reduction
in risk. A reduced risk of type 2 diabetes was also asso-
ciated with cereal fibre (RR 0.39). Data pooled from
seven prospective cohort studies (including the Mon-
tonen study) provided a summary estimate of a 30%
reduction in risk (RR 0.70) (Liu 2003). In this paper the
author highlights the need to distinguish between the
biological effects of wholegrain and those of refined-
grain products, to help clarify the message that should
be communicated to the public.
Several studies have also shown an inverse relation
between GI/GL and risk of developing diabetes, for
example:
The Nurses Health Study found for comparing high-
est GI with lowest GI, the RR of developing diabetes
was 1.37. The GL was also associated with diabetes (RR
1.47), and a high GL combined with a low cereal fibre
intake (< 2.5 g/day) increased the risk of diabetes fur-
ther (RR 2.50) (Salmeron et al. 1997a).
Similarly, in the Health Professionals’ Follow-Up
Study, men with a high-GI diet had an increased risk of
diabetes (comparing the highest with the lowest quintile,
RR 1.37). Those men with a high-GL diet and a low
cereal fibre intake (< 2.5 g/day) had a further increased
risk (RR 2.50 compared to men with a low-GL diet and
high cereal fibre intake) (Salmeron et al. 1997b).
In contrast, The Iowa Women’s Health Study, while
demonstrating a negative association between cereal
fibre intake and risk of diabetes, found no significant
association between GI or GL and diabetes incidence
(Jenkins et al. 2002). However, an elderly cohort was
used in this study, which could have introduced selec-
tion bias (Augustin et al. 2002).
Management of diabetes Currently the evidence base is
strong for the role of a high-carbohydrate high-fibre diet
in improving glycaemic control for people with type 1 or
2 diabetes (Mann 2001) and a higher fibre intake has
been associated with better glycaemic control in people
with type 1 diabetes (Buyken et al. 1998). A recent RCT
demonstrated that, in people with type 2 diabetes, a
high-fibre diet (containing 25 g soluble fibre and 25 g
insoluble fibre) could decrease blood glucose and insulin
more than a diet of equivalent macronutrient and energy
content, containing moderate amounts of fibre
(Chandalia et al. 2000). It is worth noting that the
amount of fibre used in this study (50 g) is high. The
current UK recommendation for adults is 18 g a day and
the average UK intake of fibre in 2000/2001 was 15.2 g
for men and 12.6 g for women (Henderson et al.
2003a). Additionally, the method used for measuring
fibre in the USA differs from that used in the UK (see
section 3.5.1), making comparisons difficult.
There is also a role for low-GI foods in the manage-
Nutritional aspects of cereals 133
© 2004 British Nutrition Foundation Nutrition Bulletin, 29, 111– 142
ment of diabetes. Medium-term studies have shown that
improvements in glycaemic control can be seen when
people with diabetes replace high-GI foods with low-GI
foods, such as wholegrain, minimally refined cereal
products (Willett et al. 2002). For example, a ran-
domised, crossover study by Jarvi et al. (1999) demon-
strated that a low-GI diet improved glycaemic control as
well as decreasing LDL-C and normalising fibrinolytic
activity compared to a high-GI diet, identical for macro-
nutrient composition and amount of dietary fibre.
Although long-term studies are required to establish the
long-term consequences, the GI concept is often used
when counselling people with diabetes.
3.4.5 Digestive health
Insoluble fibre, which is found in a range of foods
including cereals, may be important for gut health.
Insoluble fibre absorbs fluid, increasing stool weight. It
also promotes the growth and activity of the gut bacte-
ria, which could also be beneficial for gut health.
Recently, a small study demonstrated that moderate
intakes of high-fibre wheat and high-fibre rye foods
could improve other markers of gut health, such as
decrease faecal beta-glucoronidase, secondary bile acids
and para-cresol concentrations, and decrease faecal
pH, compared with a low-fibre diet (McIntosh et al.
2003).
From their work in Africa, Burkitt and Walker sug-
gested the importance of dietary fibre for digestive
health, and a role in particular for preventing colorectal
cancer. The World Cancer Research Fund currently lists
NSP/fibre as a possible factor in decreasing the risk of
colorectal cancer (World Cancer Research Fund 1997),
although a UK report concluded that there was moder-
ate evidence that diets rich in fibre would reduce col-
orectal cancer (Department of Health 1998). Since this
report several other studies have been published. A
study of ~455 000 older women with relatively low fibre
intake followed for a mean of 8.5 years found little evi-
dence that dietary fibre intake lowered the risk of col-
orectal cancer. However, this study was set up to
investigate breast cancer and not colorectal cancer, and
the highest quintile only had an average fibre intake of
~17 g a day (Mai et al. 2003).
Two more recent studies have investigated the intake
of dietary fibre and the incidence of colorectal cancer.
The European Prospective Investigation into Cancer
and Nutrition (EPIC) study followed more than 50 000
subjects aged 25–70 years for almost 2 million person-
years. An inverse relationship between dietary fibre in
foods and incidence of large bowel cancer was found,
with an adjusted RR in the highest vs. lowest quintile
of fibre from food of 0.58 (0.41–0.85). No food source
of fibre was found to be significantly more protective
but the results suggested that in populations with a
low average intake of dietary fibre, doubling of total
fibre intake from foods could reduce the risk of col-
orectal cancer by 40% (Bingham et al. 2003). Another
study performed within the Prostate, Lung, Colorec-
tal, and Ovarian Cancer Screening Trial found high
intakes of dietary fibre were associated with a lower
risk of colorectal adenoma, those in the highest quin-
tile having a 27% decrease in risk compared to those
in the lowest quintile. Fibre from cereals and from
fruits showed the strongest inverse association (Peters
et al. 2003). Intakes in the highest quintiles of these
tow studies were more than 30 g of fibre a day, at least
double the current average UK intake. The results from
these last two studies are in contrast to those of a
review of RCTs in this area which found no evidence
to suggest that increased dietary fibre would reduce the
incidence or recurrence of adenomatous polyps within
a 2–4-year period (Asano & McLeod 2002).
The role of fibre in the treatment of other bowel prob-
lems has been investigated. The faecal bulking action of
insoluble fibre makes it useful in the treatment of con-
stipation and diverticular disease (Thomas 1994). In the
past, a high-fibre diet was the normal treatment for irri-
table bowel syndrome, but a recent review by Burden
(2001) revealed a move-away from this approach,
towards manipulation of the fibre fractions in the diet,
dependent on the individual’s symptoms.
3.4.6 Other cancers
Fibre may also decrease the risk of pancreatic and breast
cancer (WCRF 1997). A series of case–control studies in
Italy found an inverse association between wholegrain
food intake and the risk of a range of cancers, including
those of the upper gastrointestinal tract, the bladder and
the kidney (La Vecchia et al. 2003). Cereals may have a
protective effect on hormone-related cancers because of
their lignan content (Goldberg 2003). Lignans, a type of
phytoestrogen, are modified by gut bacteria to be more
similar in structure to mammalian lignans (Truswell
2002).
3.4.7 Hypertension
Hypertension or high blood pressure (defined in the
guidelines of the European Society of Hypertension as
>140/90 mmHg) is a major risk factor for CVD and
renal disease (Hermansen 2000). Changes in sodium
134 Brigid McKevith
© 2004 British Nutrition Foundation Nutrition Bulletin, 29, 111 –142
intake have been shown to affect blood pressure in
older people and those with hypertension and diabetes,
but more recently a food-based approach has been
investigated. The Dietary Approaches to Stop Hyper-
tension (DASH) studies focused on increasing consump-
tion of a range of foods including wholegrain cereals,
but with particular emphasis on fruits and vegetables,
and low-fat dairy products. The DASH diet demon-
strated a strong effect on hypertension, with a decrease
in systolic blood pressure (SBP) of 11.4 mmHg and in
diastolic blood pressure (DBP) of 5.5 mmHg among
those hypertensive subjects (n = 133) (Appel et al.
1997). The benefits seen with the DASH diet may in
part be due to its high fibre content, and several studies
have specifically looked at the effect of fibre on blood
pressure, for example:
In a double-blind RCT, dietary fibre given as a sup-
plement (7 g/day) was found to significantly reduce DBP
among hypertensive patients (n = 32) compared to those
receiving a placebo (n = 31) (Eliasson et al. 1992).
•A pilot RCT involving 18 hypertensive patients found
the addition of 5.52 g beta-glucan/day decreased SBP by
7.5 mmHg and DBP by 5.5 mmHG. Virtually no change
was seen in the control group (Keenan et al. 2002).
Another small RCT study of hypertenisve patients
(n = 88) found that by including a wholegrain oat
cereal, more patients in the oats group could stop or
reduce their anti-hypertensive medication (77% vs.
42%). Those in the oat group whose medication was
not reduced had substantial decreases in blood pressure,
suggesting that wholegrain oats can have a beneficial
effect on blood pressure (Pins et al. 2002).
Although the exact effect (if any) of fibre and/or cere-
als on blood pressure is not known, current recommen-
dations encourage a whole-diet approach, along with
lifestyle modifications such as achieving a healthy
weight, regular physical activity, limiting alcohol intake,
stop smoking and being physically active. In addition to
helping control blood pressure, these recommendations
will have a wide range of beneficial effects on other
areas of health.
3.4.8 Food intolerance and allergy
There are hundreds of different foods which may cause
adverse reactions in certain individuals and cereals con-
taining gluten (defined currently by the EU to include
wheat, rye, barley, oats and spelt or their hybridised
strains) are recognised as one of the more common
causes of intolerance (Buttriss 2002).
A specific intolerance to gluten can cause coeliac dis-
ease, which leads to inflammation of the small intestine
and malabsorption. In the past the prevalence of coeliac
disease in the UK has been estimated at 1 case in 1 500
people. However, the use of serological screening tests
suggests the true prevalence may be higher – a study in
Belfast has suggested a prevalence of 1 in 130 (Buttriss
2002). Traditionally, wheat, rye, barley and oats and
products containing these cereals have been avoided.
However, recently a small study of 15 coeliac disease
patients in remission, who included large amounts of
oats in their diets, found no adverse effects over a 2-year
period (Størsrud et al. 2003). Similarly, work by Jana-
tuinen et al. (2002) also found that there were no sig-
nificant differences in people with coeliac disease
between those consuming oats for 5 years and controls.
Although contamination of oats with wheat, rye and
barley during harvesting, transportation and milling is
possible, several studies have reported no effects of trace
amounts of gluten, either to the small intestine mucosa
or gastrointestinal symptoms.
3.5 Labelling and health claims
3.5.1 Labelling
In the UK, nutrition labelling is not mandatory but if a
claim is made nutrition information must be given. The
two current formats are the Group 1 declaration
(energy, protein, carbohydrate and fat) and Group 2
(as for Group 1 plus sugar, saturates, fibre and
sodium). In the UK the Englyst method, which mea-
sures only the NSP component, has been used to calcu-
late the fibre content of foods. Other EU countries and
the USA use the American Association of Analytical
Chemists (AOAC) method, which also measures lignin
and resistant starch, leading to a higher value when
compared with that found using the Englyst method. In
December 2000, the Food Standards Agency issued a
notice to inform the food industry that the AOAC
method would now be used in order to harmonise free
trade.
With regard to ingredient labelling, an amendment
has been agreed to the EU Directive on food labelling
(2000/13/EC). This will require common foods and
ingredients causing allergic reactions to be labelled –
currently some exemptions exist. Cereals containing
gluten, i.e. wheat, rye, barley, oats (although this may
change due to new research that is emerging, such as
that mentioned in section 3.4.7), spelt or their hybri-
dised strains, and products derived from these foods,
will be included in this proposal.
Nutritional aspects of cereals 135
© 2004 British Nutrition Foundation Nutrition Bulletin, 29, 111– 142
The GI concept (discussed in earlier sections) has been
used in the management of diabetes in a number of
countries, including Australia where they have devel-
oped licensed GI labelling on pre-packaged foods
(Nantel 2003). There are several methodological con-
siderations in determining the GI of a food, e.g. the rise
in blood glucose is highest at breakfast (after a 10–12-h
overnight fast) and there is variability within and
between subjects (so tests should be repeated three times
with each subject to obtain a representative mean).
However, there is interest in bringing this concept into a
UK public health context and several laboratories will
soon offer GI testing.
3.5.2 Health claims
As more is learnt about diet and health, there is an
increased need and justification to communicate positive
health messages, and health claims are one method that
may be used. Although legislation specifically covering
health claims does not currently exist in the UK, in the
USA, where there is such legislation, currently approved
claims include those associating:
soluble fibre from certain foods and the risk of CHD;
diets low in saturates and cholesterol and high in
fruits, vegetables and grain products that contain fibre,
particularly soluble fibre, with reduced risk of heart dis-
ease.
In Sweden, eight generic relationships have been rec-
ognised including constipation and dietary fibre, and
soluble fibre and blood cholesterol. In 2002, the UK
Joint Health Claims Initiative approved a claim for
wholegrain foods and heart health (‘people with a
healthy heart tend to eat more wholegrain foods as part
of a healthy lifestyle’), with wholegrain foods defined as
those containing 51% or more wholegrain cereals.
EU legislation on health claims has been proposed
which potentially will limit the types of foods that will
be allowed to carry claims. As well as prohibitions on
non-specific claims, claims regarding psychological and
behavioural functions and health claims on alcohol,
the proposal outlines plans to evaluate the ‘nutritional
profiles’ of foods, with a view to restricting the use of
claims on some foods with high fat, high salt and/or
high sugar contents. A pre-approval process is
planned, which will require submission of a dossier
containing relevant scientific evidence, prior to
approval of a health claim (further information can be
found at http://europa.eu.int/prelex/detail_dossier_real.
cfm?CL=en&DosId=184390).
3.6 Consumer understanding
Generally it appears that many consumers believe their
diet is healthy. For example, in an EU survey, 71% of
respondents thought they had no need to change what
they were eating. Additionally, almost half of people did
not think about the nutritional aspects of the foods they
eat (Kearney et al. 1997). It seems that nutrition/healthy
eating does not have a top priority for some people
(Kearney et al. 2000). Although the UK has no specific
recommendations for servings of wholegrain foods per
day, evidence from dietary surveys suggests intakes are
low. For example, about 30% of UK adults had no
wholegrain foods during the period of survey (1 week)
and over 97% did not meet the US recommendation of
three servings per day (Lang & Jebb 2003). It has been
suggested that some consumers may find it difficult to
identify wholegrain foods; some people believe they do
not have the necessary skills to prepare and cook
wholegrain foods while others think wholegrain foods
may be bland and dry tasting (Lang & Jebb 2003).
Work in Australia found that the relationship
between fibre intake and its food sources was relatively
well understood, although confusion still existed about
specific food sources of fibre (Cashel et al. 2001). How-
ever, it has been shown that it is possible to change con-
sumers’ purchasing habits through health promotion.
An advertising campaign in the USA highlighting the
possible benefits of a high-fibre, low-fat diet in prevent-
ing some types of cancer increased the purchase of high-
fibre cereal (Levy & Stokes 1987).
There appears to be a belief among some members of
the public that carbohydrate-based foods, such as
cereals, are high in energy and ‘fattening’, while other
individuals see these foods as nutritious and good for
health (Stubenitsky & Mela 2000). High-protein, low-
carbohydrate diets are growing in popularity and,
although short-term weight loss may occur, this is most
likely because of decreased energy intake. There is a lack
of information regarding the long-term effects of carbo-
hydrate restriction and health professionals have
expressed concerns for people with underlying health
problems (e.g. CVD, type 2 diabetes and those with
impaired liver and kidney function) (Stanner in press).
In the UK, there appears to be a misconception
regarding the incidence of allergy and intolerance,
including cereals such as wheat, with many more people
believing themselves to have a problem than the evi-
dence would suggest. For example, one survey found
that 20% of adults believed they had a food intolerance
while in reality food intolerance in total is estimated to
affect 5–8% of children and 1–2% of adults, while the
136 Brigid McKevith
© 2004 British Nutrition Foundation Nutrition Bulletin, 29, 111 –142
prevalence of food allergy is estimated to affect 1–2% of
children and less than 1% of adults (Buttriss 2002).
3.7 Key points
Cereals have been part of the human diet since pre-
historic times. They are staple foods, and cereals and
cereal products are an important source of energy, car-
bohydrate, protein and fibre. They also contain a range
of micronutrients such as vitamin E, some of the B vita-
mins, sodium, magnesium and zinc. Because of the man-
datory fortification of some cereal products (e.g. white
flour and therefore white bread) and the voluntary for-
tification of others (e.g. breakfast cereals), they also con-
tribute significant amounts of calcium and iron. There is
growing interest in the phytochemicals cereal foods con-
tain and the potential health benefits these substances
may provide.
There is evidence to suggest that regular consump-
tion of cereals, specifically wholegrains, may have a
role in the prevention of chronic diseases. The strength
of evidence varies and although cause and effect has
not currently been established, people who consume
diets rich in wholegrain cereals seem to have a lower
incidence of many chronic diseases. It remains to be
established whether this is a direct effect, or whether
wholegrain consumption is merely a marker of a
healthy lifestyle.
The exact mechanisms by which cereals convey ben-
eficial effects on health are not clear but it is likely they
are multifactorial and may be related to their micronu-
trient content, their fibre content and/or their GI.
As there may be a number of positive health effects
associated with eating wholegrain cereals, encouraging
their consumption seems a prudent public health
approach. However, as cereals and cereal products con-
tribute a considerable proportion of the sodium intake
of the UK population, manufacturers need to continue
to reduce the sodium content of foods such as breakfast
cereals and breads where possible.
•Nutrition labelling is currently not mandatory in the
UK, although many manufacturers provide information
voluntarily. The fibre content of most UK foods is still
measured by the Englyst method rather than the AOAC
method used by other EU countries and the USA and
now recommended by the UK’s Food Standards Agency.
Currently, UK recommendations for fibre intake relate
to the Englyst method, and hence need revision.
Changes to EU labelling regulations will see the labelling
of common foods and ingredients causing allergic reac-
tions, including cereals containing gluten, and the intro-
duction of EU legislation covering health claims may
help consumers identify foods with proven health ben-
efits.
Several misconceptions exist among the public with
regard to cereals and cereal products. Firstly, many
more people believe they have a food intolerance or
allergy to these foods than evidence would suggest and,
secondly, cereals are seen by some as ‘fattening’. The
public should not be encouraged to cut out whole food
groups unnecessarily. As cereals and cereal products
provide a range of macro- and micronutrients, eliminat-
ing these foods without appropriate support and advice
from a state-registered dietitian or other health profes-
sional could lead to problems in the long term.
4Future developments
With advances in technology, there are now a number of
ways in which cereals and their products can be
enhanced. Traditional plant breeding is still an impor-
tant tool [e.g. breeding for improved selenium uptake
and/or retention (Lyons et al. 2003)], but it is also pos-
sible to change the nutrient content of cereal products
through fortification and through genetic manipulation
of the crop. Further research into the processing of cere-
als and production of cereal products may also improve
overall nutrient content. Another area of interest is the
interaction between genes and nutrients (see section
4.3). While technology may provide opportunities, it is
important to consider the long-term consequences and
consumer acceptability of new technology.
4.1 Fortification
As discussed earlier in section 3.3, flour (except whole-
meal) in the UK is fortified with calcium, iron, thiamin
and niacin. A number of other cereal products are for-
tified voluntarily, with the best example being some
breakfast cereals which are fortified with a range of B
vitamins, vitamin D, iron, vitamin C, vitamin E, beta-
carotene and zinc (Buttriss 1999). Although some other
cereal products are fortified with folic acid (the man-
made form of the B vitamin folate), cereal products in
America have been fortified with folic acid by law since
1997 and, recently in the UK, there has been debate
regarding mandatory fortification of flour with folic
acid.
Folic acid supplementation in the early weeks of preg-
nancy can protect against neural tube defects (NTD). All
women of child-bearing age who may become pregnant
are advised to take daily supplements (400 mg) of folic
Nutritional aspects of cereals 137
© 2004 British Nutrition Foundation Nutrition Bulletin, 29, 111– 142
acid but in 2000/2001 more than 80% of this subgroup
of the population had intakes from all sources below
400 mg (Henderson et al. 2003b). Additionally, many
pregnancies are unplanned. Poor folate status is also
associated with high homocysteine levels, an emerging
risk factor for CVD, though it has yet to be demon-
strated in RCTs that improvements in folate status
reduce cardiovascular mortality. On the other hand,
high intakes of folic acid may mask vitamin B12 defi-
ciency, which causes a form of anaemia and is some-
times seen in elderly people. Estimates of vitamin B12
deficiency in the over 65s in the UK range from 1 in 500
to 1 in 15. If such a deficiency is not identified early
enough then there is a possible risk of neurological dam-
age. However, folate deficiency is also thought to be
commonplace in elderly people (NDNS information
from 1994/1995 found 1% of men and 6% of women
aged 65 or older had inadequate folate intakes; Finch
et al. 1998), posing a real dilemma for public health
policy makers.
In America, rates of NTD births fell by 20% in 1 year
and heart attacks among the elderly fell by 3.4% fol-
lowing folic acid fortification, but generally there is little
evidence from other countries of the impact of folic acid
fortification, especially on the prevalence of vitamin B12
deficiency. In 2000, the UK’s Committee on Medical
Aspects of Food proposed that flour be fortified with
folic acid (240 mg folic acid/100 g flour) (Department of
Health 2000). In 2002, after wide consultation, the
Food Standards Agency decided against recommending
mandatory fortification. As more information becomes
available especially on the risk to those groups with low
vitamin B12 status and the benefits for pregnant women
and possible heart health benefits, this area should be
revisited.
4.2 Genetic modification
As well as the possibility of manipulating the expression
of native genes for disease resistance, novel genes may
also be used, e.g. using virus-derived sequences to
develop virus-resistant plants. It is also possible to
develop transgenic cereals with resistance to herbicides,
decreasing the need for herbicide use. Genetic modi-
fication also offers the possibility of improving the
nutritional properties of cereals. Examples include
increasing the oligosaccharide, polysaccharide and iron
levels in cereals, enhancing vitamin E levels in corn and
developing rice containing beta-carotene and rice con-
taining iron (Henry 2001; Khush 2001; Lucca et al.
2002).
4.3 Gene–nutrient interactions
Some of the genes involved in the digestion and absorp-
tion of carbohydrate have been shown to be polymor-
phic or to show rare deficiency variants (e.g. glucose and
galactose malabsorption due to lack of the appropriate
transporter in the small intestine) (Swallow 2003).
Although some single genes are being identified, the
genetic component for chronic diseases such as type 2
diabetes, heart disease and obesity are mainly multifac-
torial (Williams 2003). For example, a subtype of type 2
diabetes has been associated with the genetic markers
ADA and DS20S16 on chromosome 20q and abnormal-
ities in the glucokinase gene on chromosome 7p. How-
ever, people without either of these genetic linkages can
also have type 2 diabetes (Neel 1999).
As the knowledge base on gene nutrient interactions
grows, it may be possible to target specific nutrition
messages to people with specific genetic profiles,
although such an approach is probably a way off,
largely because of the complexity referred to above.
With regard to research into nutrition and health,
genetic variation is an important consideration and one
that should be addressed in future studies. It has been
suggested that genotyping of subjects in RCTs be per-
formed prospectively, allocating subjects of each geno-
type randomly to each treatment (Mathers 2003).
However, this will add to the complexity of the study,
influencing recruitment, study length and cost.
4.4 Key points
Fortification of white flour with folic acid (the man-
made form of the B vitamin folate) has been proposed in
the UK, to decrease the rate of NTD. Such a move could
also have a benefit for heart health as poor folate status
is associated with high homocysteine levels, an emerging
risk factor for CVD. However, high intakes of folic acid
can mask vitamin B12 deficiency a condition that occurs
more frequently with age and has serious neurological
symptoms affecting the peripheral nervous system.
The disease resistance of cereal crops can be increased
by manipulating the expression of native genes. Novel
genes may also be used for this purpose as well as for
developing cereals with resistance to herbicides, and
cereals with improved nutritional properties (e.g.
increased levels of iron and rice containing beta-caro-
tene). The long-term consequences and consumer
acceptability of such advances must be considered and
consumer choice maintained.
Knowledge of the interactions between genes and
138 Brigid McKevith
© 2004 British Nutrition Foundation Nutrition Bulletin, 29, 111 –142
nutrients continue to grow and in the future it may be
possible to target specific nutrition messages to people
with specific genetic profiles.
5Conclusions and recommendations
Cereals have been a mainstay of the diets of people
worldwide, since records began. Even with the diversity
of foods now available, cereals remain a fundamental
part of the dietary pattern, providing energy and fibre,
and a range of nutrients, such as carbohydrate, protein,
B vitamins, vitamin E, iron, magnesium and zinc. For-
tified cereal products such as white bread and breakfast
cereals are important sources of nutrients for both chil-
dren and adults, although sodium levels of these and
other processed cereal foods should continue to be
reduced to help people to lower their overall sodium
intake.
It is now recognised that cereals can also provide
other bioactive substances, such as lignans, which may
prove important for health. Further research is required
in this area, including identification of other substances
within cereals and their bioavailability.
Currently, most of the evidence for the health benefits
of cereal foods relates to wholegrain foods and their
fibre content and/or their low GI, although other factors
may also be involved (e.g. resistant starch, micronutri-
ents and bioactive substances in wholegrain cereals). To
increase consumption of wholegrain foods, it may be
useful to have a quantitative recommendation. Addi-
tionally, a wider range of wholegrain foods that are
quick and easy to prepare would help people increase
their consumption of wholegrain foods.
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Glossary
Caryopsis: the fruit of cereal, commonly referred to as
the grain.
Conditioning: the use of heat in tempering.
Couscous: a food product prepared from wheat semo-
lina (T. durum).
Decortication: also referred to as dehulling or dehusk-
ing; this process describes the complete or partial
removal of the outer layers from grains (and seeds,
fruits and nuts).
Embryo or germ: a thin-walled structure within the
cereal grain, containing the genetic material for a new
plant.
Endosperm: the main part of the grain, containing thin-
walled cells packed with starch.
Fibre: a group of substances in plant foods which can-
not be completely broken down by human digestive
enzymes. In the UK the Englyst method has been used
for determining the amount of fibre in food. This
method measures only the polysaccahride component
of dietary fibre, referred to as non-starch polysaccha-
rides (NSP), and does not include lignin and resistant
starch. Other countries and the USA use the American
Association of Analytical Chemists (AOAC) method
which also includes lignin and resistant starch.
Glume: an additional layer to the caryopsis, also
referred to as the husk.
Glycaemic index (GI): used for classifying carbohydrate-
containing foods, GI is the ‘incremental area under
the blood glucose curve after consumption of 50 g
carbohydrate from a test food divided by the area
under the curve after eating a similar amount of con-
trol food (generally white bread or glucose)’ (Ludwig
& Eckel 2002).
Glycaemic load (GL): assesses the total glycaemic effect
of the diet and is the product of dietary GI and total
dietary carbohydrate.
Goitrogen: substance that inhibits either the synthesis of
thyroid hormones, or the uptake of iodine into the
thyroid gland. Goitrogens can be found in food and
can cause goitre when there is a marginal iodine
intake.
Gristing: blending of grains prior to milling to produce
a flour of the required quality.
142 Brigid McKevith
© 2004 British Nutrition Foundation Nutrition Bulletin, 29, 111 –142
Mycotoxin: toxic chemical substance produced by cer-
tain types of mould.
Pearling: A polishing process that removes the outer
husk and part of the grain, leading to rounding of a
cereal grain.
Phytochemicals: bioactive substances found in plants
and plant-derived foods.
Relative risk (RR): used in epidemiology, it defines the
likelihood of an adverse health outcome in people
exposed to a particular risk, compared with people
who are not exposed.
Resistant starch: starch that resists digestion and is only
partially digested in the small intestine.
Temper: the addition of water to cereal grain prior to
milling.
Wheat germ: the embryo of the wheat seed which is usu-
ally discarded when wheat is milled to white flour.
Wheat germ contains most of the lipids of the wheat
grain, most of the vitamin B12, a quarter of the ribo-
flavin and a fifth of the vitamin B6.
... When not processed, they constitute rich sources of carbohydrates, oils, vitamins, fats, proteins and minerals (Goldberg, 2003, Mckevith, 2004. ...
... Microorganisms have been identified as one of the agents that destroy stored grains due to degradation of starch by microbial enzymes (Mckevith, 2004). ...
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... (2) for each paired comparison, treatments and reference treatments have the same location, cropping system, cropping management, and year; (3) grain yields and/or biomass yields were reported; (4) soil bulk density and/or soil penetration index data were reported; (5) the test crops were cereals, including wheat, maize, barley, oat, and sorghum; (6) location(s), year(s) and basic soil information of the experiment(s) were stated. Only studies with cereal crops as test crops were included; one reason is the importance of cereal crops in global food supply (FAO, 2021;McKevith, 2004), the other reason is that the results are likely more robust when using crops with similar root morphology and physiology (Shaheb et al., 2021). Grain yield and/or biomass yield were used as crop response indicators. ...
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Featured Application: The current investigation was part of a collaborative research project aiming at finding innovative decontamination strategies to prevent food waste and reintroduce safe whole wheat grain into the food value chain. Abstract: Wheat is one of the world's key staple foods, but it is often contaminated with mycotoxin-producing microorganisms, resulting in a large amount of food waste every year. The contamination of wheat grains harvested in 2020 and 2021 in Switzerland, as well as of wheat flours bought in local stores with the two mycotoxins zearalenone (ZEA) and enniatin B (ENB) was investigated. The quantification was performed using LC-MS/MS. ZEA, the level in different cereals and food products of which is regulated by law, was detected in half of the grain samples at levels below 100 µg/kg, except for one sample contaminated with 147 µg/kg. No ZEA was detected in the commercial wheat flours. The emerging mycotoxin ENB was detected in all samples of wheat grains and flours, at levels between 3 and 938 µg/kg. The harvest year was shown to affect the ENB content (p value < 0.01), and in particular the humid weather conditions encountered in 2021 during the month of harvest. The refining grade of the flours showed no influence on the contamination by ENB, indicating that the contamination with ENB can occur not only on the surface layers but also on the inner layers on the wheat grain. As chronic exposure to ENB can therefore not be excluded, decon-tamination solutions are needed to prevent food waste and further improve the food safety of wheat-based products.
... Cereals are widely consumed in various forms according to cultural, traditional, and religious practices, though they are primarily considered as significant plant-based energy sources. 4 All cereals are produced from the grains (harvested seeds) of plants classified in the grass family (Poaceae). The common term "millet" has been used for approximately 10 000 years and encompasses some of the grains that have served as plant-based human foods. ...
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... Starch is comprised of 25% amylose (a combination of linear and weakly branched) and 75% amylopectin (monodisperse and highly branched) (Maningat et al., 2009). The ratio of amylose to amylopectin within the starch granules varies, depending on the species and the cultivar (McKevith, 2004). ...
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The findings of a survey of the diet and nutrition of young people aged 4–18 years living in private households in the UK, carried out between January 1997 and January 1998. The National Diet and Nutrition Survey (NDNS) of young people aged 4–18 years forms part of the NDNS programme, which aims to provide a comprehensive, cross-sectional picture of the dietary habits, nutrient intakes and nutritional status of the British population by studying representative samples of defined age groups. The survey components included a detailed interview covering dietary habits, lifestyle and socio-demographic characteristics; a 7-day weighed dietary record; a 7-day physical activity diary; measurements of height, weight, mid-upper arm, waist and hip circumferences, and blood pressure; a blood sample for analysis of a range of nutritional status indices; a single urine sample; and an oral health interview and dental examination. A total of 1701 young people provided 7-day dietary records, representing a response rate of 64%. Results have been published in two volumes covering the diet and nutrition survey and the oral health survey. The reports present results for boys and girls separately in four age groups: 4–6 years; 7–10 years; 11–14 years and 15–18 years. Results are also presented by region and by socio-economic characteristics. This review summarises some of the main findings of the diet and nutrition survey, including: the proportion of young people who ate selected foods; energy and nutrient intakes compared with UK Dietary Reference Values; nutritional status; physical measurements; and physical activity.