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Absorption Studies Show that Phytase from Aspergillus niger Significantly Increases Iron and Zinc Bioavailability from Phytate-Rich Foods


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Iron and zinc deficiency are major public health problems affecting many parts of the world, including Southeast Asia. Infants, young children, and women of reproductive age are particularly vulnerable due to their high requirements. Even though iron and zinc are present in significant amounts in the plant-based diets typically consumed in developing countries, their bioavailability is low due to high levels of absorption inhibitors such as phytate. Phytase has been used in animal nutrition for decades to improve the bioavailability of certain minerals in feed. To show the effect of phytase in human nutrition based on evidence from human studies. Phytase can be used either during processing or as an active food ingredient degrading dietary phytate during stomach transit time. Evidence from human studies testing the effect of phytase on iron and zinc bioavailability using stable isotopes was reviewed. Twelve studies tested the effect of phytase on iron and five tested its effect on zinc bioavailability. Most of these studies used a phytase derived from Aspergillus niger. They found a beneficial effect unless phytate concentrations were too low or levels of inhibitors or enhancers of iron absorption were too high. Twenty to 320 phytase units per 100 g of flour significantly improved iron absorption, even though higher levels might further increase iron bioavailability. For zinc, not enough information is available to determine optimal activities. Phytase clearly has a beneficial effect on iron and zinc absorption from phytate-rich foods. It also has the potential to increase the absorption of magnesium, calcium, and phosphorus in areas such as Southeast Asia where mineral deficiencies are widespread.
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Food and Nutrition Bulletin, vol. 34, no. 2 (supplement) © 2013, The United Nations University.
Absorption studies show that phytase from
Aspergillus niger
significantly increases iron and zinc
bioavailability from phytate-rich foods
Background. Iron and zinc deficiency are major public
health problems affecting many parts of the world,
including Southeast Asia. Infants, young children, and
women of reproductive age are particularly vulnerable
due to their high requirements. Even though iron and
zinc are present in significant amounts in the plant-based
diets typically consumed in developing countries, their
bioavailability is low due to high levels of absorption
inhibitors such as phytate. Phytase has been used in
animal nutrition for decades to improve the bioavail-
ability of certain minerals in feed.
Objective. To show the effect of phytase in human
nutrition based on evidence from human studies. Phytase
can be used either during processing or as an active food
ingredient degrading dietary phytate during stomach
transit time.
Methods. Evidence from human studies testing the
effect of phytase on iron and zinc bioavailability using
stable isotopes was reviewed.
Results. Twelve studies tested the effect of phytase on
iron and five tested its effect on zinc bioavailability. Most
of these studies used a phytase derived from Aspergillus
niger. They found a beneficial effect unless phytate con-
centrations were too low or levels of inhibitors or enhanc-
ers of iron absorption were too high. Twenty to 320
phytase units per 100 g of flour significantly improved
iron absorption, even though higher levels might fur-
ther increase iron bioavailability. For zinc, not enough
information is available to determine optimal activities.
Conclusions. Phytase clearly has a beneficial effect on
iron and zinc absorption from phytate-rich foods. It also
has the potential to increase the absorption of magne-
sium, calcium, and phosphorus in areas such as South-
east Asia where mineral deficiencies are widespread.
Key words: Iron bioavailability, iron deficiency,
phytase, stunting, zinc bioavailability, zinc deciency
Iron and zinc deficiencies: Major public health
Iron-deficiency anemia and zinc deficiency are major
public health problems worldwide [1, 2]. Globally,
anemia affects 1.62 billion people, of whom over 500
million are women of reproductive age and about 600
million are children [3]. Infants are among the most
vulnerable groups, and their development often begins
to falter with the introduction of complementary foods
or shortly afterwards [4, 5]. Iron requirements increase
during this period of development due to rapid growth,
and stores are quickly used up, eventually resulting
in iron deficiency unless sufficient iron is taken up
[1]. This then leads to iron-deficiency anemia and its
associated pathologies, including impaired cognitive
and psychomotor development [6–8] and, later in life,
reduced work capacity [9]. The prevalence of anemia,
of which around half is thought to be caused by iron
deficiency, is high in both pregnant and nonpregnant
women of reproductive age due to increased iron
requirements and menstrual blood losses, respectively
[3]. During pregnancy, iron deficiency significantly
increases the risk of maternal and perinatal mortality
[10]. Zinc deficiency also appears to be widespread in
Southeast Asia and increases the risk of adverse preg-
nancy outcomes [11] and stunting [12]. However, the
evidence linking zinc deficiency with cognitive and
physical development is somewhat inconsistent due to
a lack of reliable biomarkers for individual zinc status.
Barbara Troesch, Hua Jing, Arnaud Laillou, and Ann Fowler
Barbara Troesch and Ann Fowler are affiliated with DSM
Nutritional Products Ltd, Kaiseraugst, Switzerland; Hua Jing
is affiliated with DSM Nutritional Products Asia Pacific, Sin-
gapore; Arnaud Laillou is affiliated with the Global Alliance
for Improved Nutrition (GAIN), Geneva.
Please direct queries to the corresponding author: Barbara
Troesch, DSM Nutritional Products Ltd, Wurmisweg 576, 4303
Kaiseraugst, Switzerland; e-mail:
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Phytase human efficacy review
High level of phytate in diets in the developing world
Diets in developing countries are typically monotonous
and plant-based, containing little or no animal prod-
ucts. Use of the minerals from such diets is inefficient,
as their bioavailability is low due to the presence of
absorption inhibitors such as phytic acid. This also
applies to vegetarian and, to an even larger degree,
vegan diets in industrialized countries. The high-
est levels of phytic acid are found in grains, legume
seeds, and linseed. For example, a study among more
than 1,000 people in Andra Pradesh, India, where
a vegetarian diet is the norm, showed high levels
of phytate in the diet [13]. In 1988, Ferguson et al.
reported that the bioavailability of minerals in Eastern
Africa was low due to the high phytic acid content of
the staple foods [14], even among children [15]. This
hypothesis can be extended to many developing coun-
tries in Southeast Asia where diets are based on rice,
green vegetables, white meat (pork and chicken), and
green tea and consequently are rich in phytates and
polyphenols. In a comparison of women of reproduc-
tive age living in urban and rural Vietnam, those in
rural areas tended to consume more cereals (412.4 vs.
370.6 g/day, p < .01) [16] and thus more dietary phytate
(214 vs.166 mg/day, p < .05) (unpublished data). Simi-
lar trends were observed among Vietnamese children
aged 6 to 59 months, with phytate intakes of 136 mg/
day in rural areas versus 47 mg/day in urban areas
(p < .01) (unpublished data). These data indicate that
women of reproductive age and children, especially
children under 5 years of age, who live in rural areas
may be at higher risks for iron and zinc deficiencies
than those in urban areas, and thus would benefit more
from adequate release of these minerals from absorp-
tion inhibitors such as phytate in the food matrices.
Adequate degradation of phytate in staple foods may
play an important role in improving micronutrient
status worldwide and in Southeast Asia, where the
prevalence of anemia is 38% among women of repro-
ductive age and 65% among preschool children [3, 17].
In Vietnam, for example, zinc deficiencies are among
the most prevalent micronutrient deficiencies, with
more than 50% of women and children under 5 years
being deficient [18].
Phytase: A potential solution to increase
Given the varying affinity of phytic acid protons to
dissociate in the pH range of the stomach and intes-
tine, phytic acid is mostly found as negatively charged
phytate [19], often in the form of mono-, di-, or
trivalent metal salts [20]. These salts have a very low
solubility under the pH conditions of the upper gas-
trointestinal tract, where most minerals are absorbed,
and they tend to precipitate with increasing pH along
the intestine [21]. Iron–phytate complexes are insoluble
in the pH range from around 2.5 to 8 [22]. It was sug-
gested that the inhibition by phytate is not so much due
to the complexing itself, but because they tend to aggre-
gate in insoluble precipitates [23]. This is supported by
the finding that the solubility of inositol phosphates, as
well as the bioavailability of minerals, decreases with
increasing level of phosphorylation [21]. Even though
some level of exchange of ligands exists, it is unlikely
that iron dissociates from the aggregates in sufficient
quantities in the duodenum, where its absorption takes
place [24]. Phytic acid can be degraded by processes
such as fermentation, soaking, germination, and malt-
ing, whereby endogenous phytases in grains and seeds
are activated, or by adding an exogenous phytase [24,
25]. A sufficient degradation of phytate will prevent
the complexing and consequently also the precipitation
of iron into insoluble complexes, thereby increasing
its bioavailability. Enzymatic phytate (myo-inositol-
hexaphosphate) hydrolysis is shown in figure 1.
Phytase has been used in animal nutrition for two
FIG. 1. Enzymatic phytate (myo-inositol-hexaphosphate) hydrolysis
+ H
1 – 5 inorganic
penta, tetra, tri, di or mono
(n) (e.g. Fe
, Zn
, Mg
n Me
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B. Troesch et al.
decades for sustainable mineral nutrition and is today
a standard ingredient in feed for monogastric animals.
Particularly in swine and poultry, dietary supplemen-
tation with phytases has had positive effects on the
availability of minerals such as phosphorus, calcium,
and zinc, and on reduction of fecal excretion of phos-
phorus [26, 27]. In human studies, the use of phytase
to date has mainly focused on the benefit for iron and
zinc absorption. The aim of this review is to summarize
the available evidence for the effect of phytase on the
bioavailability of iron and zinc. We primarily discuss
studies using stable isotopes to assess iron and zinc
absorption, as these provide the most direct measure
of changes in bioavailability and facilitate comparability
between the studies. In addition, we use evidence from
more long-term studies to support these findings and
to corroborate long-term benefits. The review focuses
on conditions of use, origins of the phytases, quantities
applied, and food matrices tested.
Conditions of use
Phytase can exert its effect during processing of
phytate-rich food, in which case it is not intended to
remain active at the time of consumption. Alternatively,
it can be used as a functional ingredient, for example,
in supplements intended for co-consumption with
phytate-rich foods. In both cases, the effect of phytase
is to improve the bioavailability of minerals from
phytate-rich foods.
Available evidence in humans
To our knowledge, 12 absorption studies investigat-
ing the effect of phytase on iron bioavailability in
humans had been published at the time of writing
[28–39] (table 1). Of these, nine used phytase to
degrade phytate during food processing [28–36], and
in three the phytase was used as a food ingredient, i.e.,
consumed as active enzyme [37–39]. The phytase was
derived from Aspergillus niger in eight of the food pro-
cessing studies [28–34, 36] and from Peniophora lycii
in one study [35]. Two of the studies feeding the active
enzyme used a phytase from A. niger [37, 39], while
the third did not state the organism that produced the
phytase [38].
Four studies of zinc absorption used phytase as a
food processing aid [34, 40–42], and in one the phytase
was used as a food ingredient directly given with the
test meal* (table 2). The phytases used were derived
from A. niger [34, 41]* or from cereals [40, 42]. A. niger
* The study has only been presented at a conference so far:
Brnic M. Effect of the enzyme phytase and EDTA on human
zinc absorption from maize porridges fortified with ZnSO
ZnO. Bioavailability Conference 2010. Asilomar Conference
Grounds, Pacific Grove, California, USA, 2010.
TABLE 1. Summary of absorption studies using phytase to improve iron bioavailability
Added iron
compound Phytase (dose) Test meal
Phytate-to-iron molar ratio
ratio Outcome
After dephyti-
Used in food processing
Hurrell et al.
1992 [28]
Native iron with
extrinsic label
Aspergillus niger
Soy protein isolate Adults (n = 8) 4.2 < 0.006 4.8 p < .001
Adults (n = 7) 3.0 < 0.005 4.0 p < .05
Davidsson et al.
1994 [29]
A. niger (NA) Soy formula Infants (n = 10) 2.1 0.4 1.2 p < .05
Infants (n = 10) 2.1 < 0.007 2.2 p < .001
Davidsson et al.
1997 [30]
A. niger (NA) White wheat- and milk powder–
based formula
Infants (n = 12) 0.6 0.08 1.0 NS
Hurrell et al.
1998 [31]
Native iron with
extrinsic label
A. niger (NA) Soy formula Adults (n = 9) 2.1 < 0.007 2.5 p < .05
Davidsson et al.
2001 [32]
A. niger (NA) Pea formula Adults (n = 10) 8.0 < 0.02 1.6 p < .0001
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Phytase human efficacy review
Hurrell et al.
2003 [33]
Native iron with
extrinsic label
A. niger (NA) Wheat porridge Adults (n = 11) 0.12%
≤ 0.002%
11.6 p < .0001
Wheat, milk NA NA 1.3 NS
Rice porridge Adults (n = 9) 0.16%
≤ 0.002%
3.1 p < .001
Oat porridge Adults (n = 10) 0.67%
≤ 0.002%
8.4 p < .0001
Maize porridge 0.26%
≤ 0.002%
5.0 p < .0001
Sorghum porridge
Adults (n = 8) 0.87%
≤ 0.002%
1.3 NS
Sorghum porridge
≤ 0.002%
1.8 p < .01
Sorghum porridge
Adults (n = 9) 0.43%
≤ 0.002%
2.0 p < .001
Sorghum porridge
≤ 0.002%
1.9 p < .01
Wheat porridge with milk Adults (n = 6) NA NA 2.5 p < .05
Wheat porridge with milk and
ascorbic acid
NA NA 2.5 p < .05
Wheat and soy porridge Adults (n = 9) 0.30%
0.02% 3.3 p < .005
Wheat and soy porridge with
ascorbic acid
NA NA 3.5 p < .005
Davidsson et al.
2004 [34]
A. niger (NA) Soy formula Infants (n = 9) 3.1 < 0.1 1.3 NS
Zhang et al.
2007 [35]
Ferric ammonium
Peniophora lycii
Oat drink Adults (n = 20
) 3.7
1.8 p < .05
Petry et al. 2010
A. niger (100
Bean porridge Adults (n = 49
) 5.8 < 0.1 1.2 NS
Dehulled bean porridge 5.7 < 0.1 4.3 p < .001
Used as active enzyme
Sandberg et al.
1996 [37]
A. niger (~ 20
FTU/100 g
Bread rolls with white wheat flour Adults (n = 10) 0.6
NA 2.0 p < .0001
Layrisse et al.
2000 [38]
NA (~ 300
FTU/100 g
Bread with white wheat flour Adults (n =14) 3.2 NA 2.0 p < .05
Iron bis-glycine
3.2 NA 1.7 p < .05
Troesch et al.
2009 [39]
A. niger (~ 320
FTU/100 g
Maize porridge Adults (n = 17) 8 NA 1.7 p < .05
NaFeEDTA Adults (n = 18) 8 NA 1.2 p < .05
NaFeEDTA Maize porridge with ascorbic acid Adults (n = 16) 8 NA 1.8 p < .01
FTU, unit of phytase activity (amount that liberates 1 µmol of inorganic phosphorus per minute from an excess of sodium phytate at 37° C and a pH of 5.5); NA, not available, NaFeEDTA, sodium iron
ethylenediaminetetraacetate; NS, not significant
a. Phytate content only, as no information was available on native iron content.
b. High-tannin sorghum.
c. Low-tannin sorghum.
d. Calculated from phytate phosphorus content assuming that all phytate is present as 6-inositol phosphate.
e. Interstudy comparison.
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B. Troesch et al.
phytase was shown to be active over a broad pH range,
including the physiological pH of the stomach [43]
and to be stable during the expected residence time at
gastric pH [39]. It is therefore a suitable candidate for
phytate degradation in the stomach as well as during
processing. Phytase from wheat, on the other hand, is
thought to be less effective for use as an active ingredi-
ent because of its low activity and stability in the lower
pH range found in the stomach in pockets where the
buffering from food is low [44].
Improvement of bioavailability and nutritional status
Table 1 shows that the majority of studies found statis-
tically significant improvements in iron absorption [28,
29, 31–33, 35–39]; the improvement in iron absorption
achieved following phytase treatment ranged from
1.0- to 11.6-fold. In the studies in which no significant
differences were observed, the low intrinsic phytate
content of the test meal, in combination with the iron
absorption-enhancing effect of added ascorbic acid
[30, 34], the inhibiting effect of milk [30, 33], or the
high levels of polyphenols [33, 36], may account for
the lack of effect. All five zinc studies showed statisti-
cally significant improvements in zinc absorption [34,
40–42]* (table 2), with improvements ranging from
1.4- to 2.0-fold.
These results are supported by a study comparing
the effects of feeding normal and dephytinized maize
flour for 12 days, in which the use of dephytinized
maize flour resulted in a decrease in soluble transferrin
receptor and zinc protoporphyrin levels [45]. In the
study with the longest feeding period to our knowledge,
phytase was used over approximately 6 months [46].
The enzyme was used as part of a home fortification
powder with 2.5 mg of iron from sodium iron ethyl-
enediaminetetraacetate (NaFeEDTA), 2.5 mg of zinc
from zinc oxide, ascorbic acid, and other nutrients in
a maize porridge compared with a control porridge
without added nutrients. Even though the beneficial
effect cannot be attributed to phytase alone, a signifi-
cant decrease in iron and zinc deficiency was observed
despite the low levels of the two minerals in the powder,
TABLE 2. Summary of absorption studies using phytase to improve zinc bioavailability
Added zinc
(dose) Test meal
molar ratio
ratio OutcomeOriginal
Used in food processing
Egli et al.
2004 [40]
Native zinc
with extrinsic
and soy
(n = 9)
6.4 0.15 1.5 p = .005
et al. 2004
niger (NA)
(n = 9)
3.6 < 0.007 1.4 p = .03
Kim et al.
2007 [41]
Native zinc
with extrinsic
A. niger (10
FTU/100 g
brown rice;
20 FTU/
100 g soy-
bean curd
High- vs.
(n = 7)
21.4 9.1 2.0 p < .001
(n = 10)
23.5 10.5 1.7 p < .001
Thacher et
al. 2009
with labeled
(0.2 g/120
(n = 34)
3.9 mg/g
2.8 mg/g
1.7 p < .001
Used as active enzyme
Brnic 2010
A. niger
(n = 15)
9 NA 1.9 p < .001
FTU, unit of phytase activity (amount that liberates 1 µmol of inorganic phosphorus per minute from an excess of sodium phytate at 37°C
and a pH of 5.5); NA, not available
a. In addition to the use of phytase, cooked brown rice in the diet was also replaced by white rice to reduce phytate content.
b. Aged 22 to 24 years.
c. Aged 66 to 75 years.
d. No information was available on activity of this phytase.
e. Phytate content only, as no information on native zinc content was available.
* Brnic M. Effect of the enzyme phytase and EDTA on human zinc absorption from maize porridges fortified with ZnSO4 or ZnO. Bioavail-
ability Conference 2010. Asilomar Conference Grounds, Pacific Grove, California, USA, 2010.
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Phytase human efficacy review
indicating potentially increased bioavailability even
with the high levels of phytate in the food matrix. The
estimated increase in bioavailability corresponds well
with the findings of a series of absorption studies con-
ducted in preparation for this long-term study, which
showed a clear additional benefit of the phytase on the
bioavailability of iron, even in the presence of ascorbic
acid and EDTA [39]. Overall, the reviewed studies pro-
vide strong evidence for a beneficial effect of phytase
on the bioavailability of iron and zinc.
Effect of subject’s age
Of the 12 studies on iron, 9 were performed in adults
[28, 31–33, 35–39] and 3 in infants [29, 30, 34]
(table 1). The infants used for comparison by Hurrell
et al. [31] were the ones reported on in the study by
Davidsson et al. [29] and are therefore not counted
again. The authors showed that the results from stud-
ies in adults can be extrapolated to assess the impact of
phytate on iron absorption in infants, since the relative
inhibitory effect was similar for both, at least for such
formula-type meals [31]. Data from infants suggest
that, whereas homeostatic regulation of iron absorption
is not fully developed in young infants at around 4 to
6 months, it is present in older infants [47]. Similarly,
in rat pups, the intestinal iron transporters divalent
metal transporter 1 and ferroportin were appropriately
regulated in response to iron supplementation by day
20, equivalent to older human infants [47].
Of the five zinc studies, three were performed in
adults [40, 41, 43]*, one was performed in children
[42], and one was performed in infants [34] (table 2).
No information on the zinc status of the infants par-
ticipating in this study is available. Therefore, it cannot
be established whether a correlation exists between
zinc status and level of absorption. However, evidence
from rat pups indicates that homeostatic regulation of
zinc absorption develops during mid to late infancy
but might not be adequate if zinc deficiency of the diet
persists [47]. One study comparing zinc absorption in
elderly and young adults showed no difference in the
inhibitory effect of phytate between the two groups
[48]. This corresponds with results from studies in
animal nutrition, where phytase has been used for
several decades and was shown to increase mineral bio-
availability in pigs independently of their age [27]. In
summary, the available evidence suggests that phytase
has a beneficial effect on iron and zinc absorption inde-
pendently of the age of the target population.
Effect of food matrix
Evidence from an in vitro study suggests that, depend-
ing on the food matrix, 50% to 80% phytate degrada-
tion can be achieved with the use of a phytase from A.
niger [44]. It was proposed that this variation stems
from differences in accessibility of the substrate based
on its location in the plant seed or on the mineral con-
tent of the matrix [44]. The test meals used to assess
the impact of phytase on iron bioavailability consisted
of soy [28, 29, 31, 34], peas [32], beans [36], or a range
of cereals [30, 33, 35, 37–39], including rice [33],
and were given in the form of drinks, infant formula,
porridges, or bread rolls (table 1). The range of food
matrices used in the studies indicates that the effect of
enzymatic dephytinization is not limited to a particu-
lar food type but can be generalized to phytate-rich
foods, at least as long as phytate is the only or the main
inhibitor of iron absorption present in the food [50]. If
foodstuffs also contain other iron absorption inhibitors,
e.g., polyphenols or milk, ascorbic acid should be used
in addition [33]. Ascorbic acid is a known enhancer
of iron absorption and has been recommended for
milk-containing diets fortified with iron [50]. Only
one study investigated the influence of milk on the
effect of phytase, with or without ascorbic acid, and
found somewhat inconsistent results [33]. One, but
not the other, substudy showed a slight but statistically
significant effect of dephytinization on iron absorption.
The effect of the phytase remained in the presence of
ascorbic acid, despite the enhanced absorption already
seen in the meal with the native phytate content due
to the presence of ascorbic acid. This added benefit of
phytase in the presence of ascorbic acid was also shown
for iron absorption from a maize-based porridge [39]
as well as from a wheat- and soy-based porridge [33].
The inhibitory effect of phytate and polyphenols is
not additive, and it is thought that phytate and poly-
phenols affect iron absorption by similar mechanisms
[36]. As a consequence, the impact of phytate removal
will be limited if the inhibiting effect of polyphenols
persists. However, polyphenols are a heterogeneous
group of compounds that vary greatly in their ability
to chelate iron [51, 52]. The inhibitory effect of poly-
phenols from tea, red wine, and cocoa is thought to be
stronger than that of polyphenols from beans, but even
among beans, differences in polyphenol composition
and content lead to varying effects on iron bioavail-
ability [36]. The importance of such intervariety dif-
ferences in polyphenol content was also highlighted
by Hurrell et al. [33], who found a positive effect of
dephytinization of low-tannin but not of high-tannin
sorghum on iron absorption.
In vitro studies of enzymatic degradation of poly-
phenols confirmed that the presence of high amounts
of these compounds can mask the beneficial effect of
dephytinization [53]. However, at lower polyphenol
levels, the addition of an exogenous phytase even
reduced the amount of iron bound to polyphenols,
*Brnic M. Effect of the enzyme phytase and EDTA on
human zinc absorption from maize porridges fortified with
ZnSO4 or ZnO. Bioavailability Conference 2010. Asilomar
Conference Grounds, Pacific Grove, California, USA, 2010.
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B. Troesch et al.
thereby potentially increasing iron bioavailability
beyond the benefit of liberating phytate-bound iron
[49]. The authors suggest that phytate hydrolysis prod-
ucts might complex polyphenols and consequently
reduce their iron-binding capacity. Addition of ascorbic
acid can also counter inhibition of iron absorption by
polyphenols [54]. Other options would be to remove
polyphenols from foods by soaking, cooking, or dehull-
ing them, or by breeding low-polyphenol varieties [36].
The zinc studies used soy-based [34, 40, 41] or
cereal-based [40–43]* meals, and all of them showed
a beneficial effect of dephytinization on zinc absorp-
tion or status (table 2). Even though less evidence is
available, the results from a rat study indicate that zinc
absorption might be inhibited by cow’s milk, most
likely by casein with a potential contribution of cal-
cium [55]. The effect of ascorbic acid on zinc absorp-
tion has not been studied as extensively as its effect
on iron absorption. The results from an absorption
study suggest that ascorbic acid does not enhance zinc
bioavailability [56]. Although the evidence is limited,
the results from Caco2-cell models indicate that some
degree of inhibition of zinc absorption by polyphenols
exists but that it is less extensive than for iron [57]. The
inhibition of absorption by polyphenols also seems to
be brought about by different mechanisms for zinc
than for iron.
In summary, phytase improves mineral bioavail-
ability from various phytate-rich foods, both when it is
used as a food ingredient, acting in the stomach of con-
sumers, and when it is used as a food processing aid,
acting during food manufacturing. The food matrix
appears to be less relevant, unless high concentrations
of other potent inhibitors or enhancers of absorption
are present.
Effect of conditions of use
In the studies that showed significant improvements
in iron absorption, phytate-to-iron molar ratios of
approximately 2:1 to 8:1 were reduced to 0.6:1 to
< 0.005:1 (table 1). In a slightly longer study, a signifi-
cant improvement in iron status was already achieved
when the ratio was reduced from 11:1 to 4:1 [45]. Based
on the evidence available from studies investigating
the effect of dephytinization with various methods,
it has been recommended that, in order to achieve a
relevant increase in iron absorption, the phytate-to-
iron molar ratio should be decreased at least to < 1:1,
and preferably to < 0.4:1 [50]. The studies that did not
show a significant improvement in iron absorption
found reductions from 0.6:1 to < 0.08:1 [30], from 3:1
to 0.1:1 [34], and from 5.8:1 to 0.1:1 [36]. In one of the
studies, the lack of effect was likely due as much to the
comparatively low initial phytate levels [30] as to the
relatively high ascorbic acid [30, 34] or polyphenol
[36] contents of the test meals. A recent review judged
a reduction to a phytate-to-iron ratio of < 6:1 in meals
containing some enhancers of iron absorption to be
sufficient [58].
The zinc studies cited show that statistically sig-
nificant effects were seen with residual phytate-to-
zinc ratios ranging from < 0.07:1 to 10.5:1 (table 2).
Since the reduction from 23.5:1 to 10.5:1 resulted in
a significant improvement of zinc absorption [41], a
relative reduction might already be beneficial, even
if the residual phytate content remains at an elevated
level. This is supported by a study investigating the
effect of dephytinization on serum zinc levels, which
found that a reduction from a phytate-to-zinc ratio
as low as 0.8:1 to 0.05:1 still had a positive impact on
apparent zinc absorption [59]. Thus, phytate inhibition
of zinc absorption may follow a dose–response rela-
tionship without a specific threshold for inhibition, as
was proposed for iron. However, zinc absorption only
increased up to twofold in the study with relatively
low phytate reduction and might further increase with
more complete phytate degradation. More evidence is
needed to draw firm conclusions.
In the three iron studies published at the time of
writing, amounts of approximately 20, 300, and 320
FTU (unit of phytase activity: the amount that liber-
ates 1 µmol of inorganic phosphorus per minute from
an excess of sodium phytate at 37°C and a pH of 5.5)
were added to 100-g portions of flour [37–39]. Despite
the differences in the amount of added enzyme, the
fold increase in iron absorption from iron sulfate was
comparable. However, this is likely due to the much
lower phytate-to-iron ratio in the study using the low
level of phytase. The rationale given in one study is that
the quantity of phytase needed was calculated assuming
that the meal contained approximately 1 g of phytate
[39]. The authors assumed that this had to be degraded
sufficiently, i.e., up to four phosphate units had to be
released per phytate molecule during the stomach resi-
dence time of approximately 60 minutes. It is reported
that phytates with five or six phosphate groups bind
iron sufficiently strongly to inhibit its absorption [60],
but there is also some evidence for an inhibitory effect
of phytates with only three or four groups, probably by
complexing iron between more than one molecule of
phytate [60]. As the phytase activity at the pH in the
stomach was estimated to be around 50% compared
with its activity under optimal conditions, 8 FTU
would be necessary to adequately degrade 1 µmol or
approximately 0.7 mg of phytate during a stomach resi-
dence time of approximately 1 hour [39]. Assuming a
phytate content of about 1 mg per 100 g of whole grain
flour, this would result in the addition of 320 FTU.
Since the increase in the absorption was less than in
*Brnic M. Effect of the enzyme phytase and EDTA on
human zinc absorption from maize porridges fortified with
ZnSO4 or ZnO. Bioavailability Conference 2010. Asilomar
Conference Grounds, Pacific Grove, California, USA, 2010.
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Copyright (c) Nevin Scrimshaw International Nutrition Foundation. All rights reserved.
Phytase human efficacy review
some of the studies in which phytate was degraded by
other means [28, 31, 33], a higher dose for meals with
comparable phytate levels might be indicated.
A study in pigs given feed containing 0, 15, and 90
FTU/100 g found a clear dose–response relationship,
with 7%, 22%, and 52% of phytate being degraded,
respectively, at the duodenal site [61]. With the higher
dose, around half of the inositol-penta-phosphate
was further hydrolyzed, and inositol-tri- and di-
phosphates dominated, whereas with the lower dose,
mainly penta-, tetra-, and tri-phosphates were found
[61]. Therefore, an increase in the dose of added
phytase might result in a more complete hydrolysis
with a further shift toward less phosphorylation and
consequently, an additional increase in bioavailability.
Degradation of higher inositol-phosphates further
along the small intestine is probably low, given the
pH conditions, the low solubility of phytate, and the
enzymatic digestion of the added phytase occurring in
the small intestine [62]. However, since iron is mostly
absorbed in the proximal part of the duodenum, later
degradation of phytate will not have a major impact
on its absorption. Evidence from a further study in
pigs indicates that complete phytate degradation, even
through the addition of exogenous phytases, is not
possible, as around one-third of it is protected from
hydrolysis due to its binding to the food matrix [21].
In summary, approximately 20 to 320 FTU per 100 g
of flour was demonstrated to improve iron bioavail-
ability significantly. Higher doses of supplementary
phytase may improve mineral bioavailability even
further, as suggested by the results of studies achiev-
ing complete dephytinization of the foods. Further
studies are warranted to explore the potential for more
complete phytate degradation during stomach transit
time. For zinc, no information on the dose in the one
study that used the active phase was published, and the
effect of dosage should be studied in future studies to
optimize the use of phytase. Some indication can be
derived from a study in rats, in which the addition of
1,000 FTU of an A. niger phytase resulted in a doubling
of apparent absorption [63].
Outlook and conclusions
Iron and zinc deficiencies remain major public health
problems, especially in developing countries, and for-
tification programs often do not achieve the expected
results due to the low bioavailability of the minerals
resulting from high levels of inhibitors of absorption,
such as phytate. For example, the median intakes of
dietary iron and zinc met less than 50% of the require-
ments for Vietnamese children [18]. Fortified rice and
wheat flour intakes provided less than 60% and 10% of
the iron and zinc requirements, respectively, to children
in Vietnam [18]. The beneficial effect of phytase will
be most pronounced on diets with very high levels of
phytate containing little or no enhancers of mineral
absorption, such as diets based on plant staples such as
maize and wheat. Although the typical complementary
foods consumed in developing countries were shown
to contain significant amounts of minerals, including
iron and zinc, these are often poorly available because
of the presence of high levels of phytate. They may
provide 2.5 to 12.0mg of iron as well as 1.0 to 10.4 of
mg zinc daily [64] that could potentially be made at
least partially available by adding phytase either during
preparation or just before consumption. This could
reduce the amount of minerals added to the diet via
fortification and supplementation. Besides cost savings,
such an approach might also have advantages from a
safety point of view, since concerns have been raised
about negative health effects of supplemental iron in
the presence of infections, particularly malaria and
diarrheal diseases [65]. Providing adequate amounts of
bioavailable iron while minimizing the intake of added
iron might therefore be advisable.
Moreover, evidence is emerging that unabsorbed
iron has a negative effect on the gut flora, shifting its
composition toward a more pathogenic profile [66].
Even though the iron complexed by phytate is not
available for absorption, it appears to be available to
the bacteria in the large intestine. Extensive phytate
degradation by microbial phytases in the colon of pigs
was shown, despite the fact that most of the phytate was
in the solid phase by that time and therefore was less
accessible to enzymes [62]. When normal and germ-
free rats were compared, a 56% difference in phytate
degradation was observed [67]. Colonic phytate degra-
dation in pigs was actually increased when less phytate
was degraded in the stomach and small intestine [62].
The increase in bioavailability as a result of the addition
of phytase makes a reduction in iron intake possible
while keeping the amount of absorbed iron constant.
Whether this reduction in unabsorbed iron translates
into a relevant impact on the gut microbiota needs to
be shown by in vitro and long-term studies.
A potential risk associated with phytase is increased
bioavailability of heavy metals such as arsenic, cad-
mium, lead, and mercury. However, data from rats
indicate no increase in cadmium uptake and only a
tendency toward increased bone lead levels following
a diet with high levels of these heavy metals as well as
a microbial phytase [68]. Blood lead levels measured
during an intervention study with phytase as part of
a micronutrient powder were unaffected by the use
of phytase (unpublished data from a study described
by Troesch et al. [46]). Moreover, improving iron
status by increasing iron bioavailability is thought to
have a positive effect on lead levels, possibly by down-
regulating transport proteins used for lead and iron
uptake [69]. The bioavailability of arsenic is already
quite high [70], and it is highly unlikely that phytase
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B. Troesch et al.
will contribute significantly to the intake of inorganic
arsenic. Mercury exposure is predominantly associated
with the consumption of fish and other seafood. Expo-
sure to mercury in cereals and a potential increase in
bioavailability with the use of phytase is therefore not
relevant. Consequently, the risk of increased exposure
to heavy metals due to the inclusion of phytase into the
largely plant-based diets in developing countries can be
regarded as minimal.
Iron and zinc deficiencies are thought to affect cog-
nitive development, and evidence, albeit somewhat
inconsistent and limited, from humans and animals
exists to support a causal relationship [71, 72]. A recent
systematic review based on available studies found a
mildly positive effect on cognitive outcomes from iron
supplementation of infants, children, and adolescents
[73]. Improving iron and zinc status, by the addition
of phytase or by other means, may therefore have a
beneficial impact on brain and mental development.
Even though the prevalence of childhood stunt-
ing decreased from approximately 40% in 1990 to
approximately 27% in 2010, it is estimated that around
171 million children aged 0 to 5 years still suffer from
impaired growth worldwide, most of them in develop-
ing countries [17]. Around 70 million preschool chil-
dren in South Central Asia and 15 million preschool
children in Southeast Asia are affected. Moreover,
stunting is estimated to be the cause of approximately
15% of deaths in children under 5 years of age, cor-
responding to 1.5 million lives lost in 2004 [74]. For
normal growth and formation of the skeleton, adequate
supplies of macronutrients, various vitamins, as well
as minerals such as calcium, phosphorus, magnesium,
and zinc, are essential [75]. Because these so-called
type II nutrients are not stored in the body outside
functional tissue and are lost if tissue is lost (such as
during weight loss in times of malnutrition), they have
to be replaced in balance to allow for tissue synthesis
needed for growth [76]. Consequently, the effect of one
of these nutrients on growth can only be studied if all
the others are available in adequate amounts [76]. Zinc
intervention studies aiming at improving growth often
show only a small benefit [77]; a potential reason for
this is that other nutrients essential for growth, such as
phosphorus, are often missing or are poorly available
from the typically monotonous, plant-based diets with
little or no animal products. Yet, specific data on the
effect of phosphorus on growth in humans are very
limited, and studies evaluating the intake of this min-
eral hardly seem to take bioavailability into account.
Phytate serves as the most important phosphorus
storage compound of the plant [19], with 60% to 80%
of phosphorus bound to this molecule [78]. Phytase is
added to animal feed to reduce the amount of added
phosphorus by improving the absorbability of phytate–
phosphorus, while still allowing for rapid growth of
the animals [78]. This makes a strong case for the
essentiality of phosphorus for physical development.
Its role in catch-up growth as well as the prevention of
stunting should be studied in humans in more detail,
as this might be another application where the addition
of phytase is potentially beneficial. To our knowledge,
no study has examined the effect of the phosphorus
released from phytate by the addition of phytase on
growth in infants, but, given its importance in bone
formation [75], a beneficial effect is conceivable.
The evidence summarized in this review clearly
shows the beneficial effect on iron and zinc absorp-
tion of phytase added either during processing or as
an active food ingredient. It makes a strong case for
using the enzyme to improve mineral bioavailability
from plant-based foods in developing countries, but
also from vegetarian diets in the Western world. Fur-
ther studies can be expected to strengthen the case for
phytase use to improve growth and cognitive develop-
ment thanks to its impact on the absorption of iron,
zinc, calcium, magnesium, and phosphorus, especially
in Southeast Asia, one of the regions most affected by
iron and zinc deficiencies.
Barbara Troesch, Hua Jing, and Ann Fowler are
employed by DSM Nutritional Products Ltd., a pro-
ducer of enzymes for human consumption, including
a phytase from Aspergillus niger.
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... Phytic acid chelates important cations, forming insoluble complexes in the upper GIT. The use of phytase can reduce the negative effects of phytic acid on the utilization of trace elements [2,27]. Dietary fibers negatively affect the absorption of trace elements in the GIT due to mineral binding or physical entrapment [3]. ...
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This study investigated the effects of supplementing phytase and non-starch polysaccharide-degrading enzymes (NSPases) to corn–soybean meal-based diet on the growth performance, trace element deposition, and intestinal health of growing–finishing pigs. Fifty pigs were randomly assigned into the control (basal diet), phytase (basal diet + 100 g/t of phytase), β-mannanase (basal diet + 40 g/t of β-mannanase), β-glucanase (basal diet + 100 g/t of β-glucanase), and xylanase (basal diet + 100 g/t of xylanase) groups. The results show that the supplementation of phytase and NSPases had no impacts (p > 0.05) on the growth performance of pigs. Compared with the control group, pigs fed with xylanase had higher (p < 0.05) Zn concentrations in the ileum and muscle and those fed with phytase had higher (p < 0.05) Zn concentrations in the ileum. Phytase and xylanase supplementation decreased (p < 0.05) fecal Zn concentrations in pigs compared with the control group (p < 0.05). In addition, phytase, β-mannanase, β-glucanase, and xylanase supplementation up-regulated (p < 0.05) the FPN1 expression, whereas xylanase up-regulated (p < 0.05) the Znt1 expression in the duodenum of pigs compared with the control group. Moreover, phytase, β-glucanase, and xylanase supplementation up-regulated (p < 0.05) the jejunal Znt1 expression compared with the control group. The intestinal morphology results show that the phytase, β-mannanase, and xylanase groups had increased villus heights (VHs), an increased villus height–crypt depth ratio (VH:CD), and decreased crypt depths (CDs) in the duodenum, whereas phytase, β-mannanase, β-glucanase, and xylanase groups had decreased VH and VH:CD, and increased CD in the jejunum compared with the control group (p < 0.05). Pigs fed with exogenous enzymes had decreased bacterial diversity in the cecum. The dietary supplementation of NSPases increased the relative abundance of Firmicutes and decreased spirochaetes (p < 0.05). Compared with the control group, dietary NSPase treatment decreased (p < 0.05) the opportunistic pathogens, such as Treponema_2 and Eubacterium_ruminantium. Moreover, the relative abundances of Lachnospiraceae_XPB1014 and Lachnospiraceae were enriched in the β-glucanase and β-mannanase groups (p < 0.05), respectively. In conclusion, phytase and xylanase supplementation may promote zinc deposition in pigs. Additionally, the supplementation of NSPases may improve the gut health of pigs by modulating the intestinal morphology and microbiota.
... Microbial phytases are also of great interest to industry due to their high level of production and extracellular activity(Cangussu et al., 2018).Of the microorganisms, fungi, bacteria and yeast are effective in phytase production, with fungi giving better results(Patel et al., 2017;Parhamfar et al., 2015) while over 200 fungal isolates, mainly Aspergillus, Mucor, Penicillium and Rhizopus have been tested. Among these Aspergillus niger phytase exhibited activity over a broad pH range, including that of the stomach and is stable during the expected residence time(Gupta et al., 2013;Troesch et al., 2013). It also produces heat stable commercial phytases, a pre-requisite in food processing involving heat treatment(Sharma Vivek, 2017). ...
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Plant-based foods constitute an important source of carbohydrates, protein, dietary fiber and vitamins. They are also associated with anti-nutrients, whose presence result in low bioavailabity of several micronutrients causing metabolic disorders related to the nutritional factors. Of prime concern for human nutrition and health management is phytic acid. In this review the effect of phytase application on micronutrient content and bioavailability of plant-based foods was critically analyzed. PubMed and Google scholar databases were searched for articles using phytase, phytase application in cereals, plant-based foods, micronutrients and deficiency as keywords. A total of 105 articles were obtained out of which 39 were included in the review. Results indicate that application of exogenous phytase to plant-based foods increases micronutrient content and bioavailability alongside improvements in baking and brewing.
... They concluded that phytase promotes the absorption of iron and zinc from phytate-rich meals and can potentially improve magnesium, calcium, and phosphorus absorption. 75 The dose-dependent inhibitory impact of sodium phytate on iron absorption was investigated by Hallberg et al. Wheat rolls with no phytates and including seven dose levels from 2 and 250 mg were served to humans. ...
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Iron is an essential element for human life since it participates in many functions in the human body, including oxygen transport, immunity, cell division and differentiation, and energy metabolism. Iron homeostasis is mainly controlled by intestinal absorption because iron does not have active excretory mechanisms for humans. Thus, efficient intestinal iron bioavailability is essential to reduce the risk of iron deficiency anemia. There are two forms of iron, heme and nonheme, found in foods. The average daily dietary iron intake is 10 to 15 mg in humans since only 1 to 2 mg is absorbed through the intestinal system. Nutrient-nutrient interactions may play a role in dietary intestinal iron absorption. Dietary inhibitors such as calcium, phytates, polyphenols and enhancers such as ascorbic acid and proteins mainly influence iron bioavailability. Numerous studies have been carried out for years to enhance iron bioavailability and combat iron deficiency. In addition to traditional methods, innovative techniques are being developed day by day to enhance iron bioavailability. This review will provide information about iron bioavailability, factors affecting absorption, iron deficiency, and recent studies on improving iron bioavailability.
... Another key strategy for increasing iron absorption from diets is by reducing the dietary phytic acid content (23), through the introduction of the phytase enzyme into grain flours (24), but requires specific conditions for effective enzymatic activity (25). This strategy will be effective only if most phytate is removed. ...
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Iron deficiency and anemia are common in low- and middle-income countries. This is due to a poor dietary iron density and low iron absorption resulting from the high inhibitory phytic acid content in cereal and millet-based diets. Here, we report that a naturally occurring low phytic acid finger millet accession (571 mg 100 g ⁻¹ ), stable across three growing seasons with normal iron content (3.6 mg 100 g ⁻¹ ), increases iron absorption by 3-folds in normal Indian women. The accessions differing in grain phytic acid content, GE 2358 (low), and GE1004 (high) were selected from a core collection of 623 accessions. Whole genome re-sequencing of the accessions revealed significant single nucleotide variations segregating them into distinct clades. A non-synonymous mutation in the EcABCC phytic acid transporter gene between high and low accessions could affect gene function and result in phytic acid differences. The highly sensitive dual stable-isotope erythrocyte incorporation method was adopted to assess the fractional iron absorption. The low phytic acid accession resulted in a significantly higher iron absorption compared with the high phytic acid accession (3.7 vs. 1.3%, p < 0.05). The low phytic acid accession could be effective in preventing iron deficiency in regions where finger millet is habitually eaten. With its low water requirement, finger millet leaves low environmental footprints and hence would be an excellent sustainable strategy to mitigate iron deficiency.
... 61 Finally, phytase could be added to supplements and micronutrient powders to help make calcium and the other divalent cations more available. [62][63][64][65] Nixtamalization Nixtamalization is a process that refers to soaking boiled corn overnight in a lime solution of calcium hydroxide. 66 After soaking, some of the outer layer of the corn, which can contain aflatoxins, is removed. ...
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Calcium intake remains inadequate in many low‐ and middle‐income countries, especially in Africa and South Asia, where average intakes can be below 400 mg/day. Given the vital role of calcium in bone health, metabolism, and cell signaling, countries with low calcium intake may want to consider food‐based approaches to improve calcium consumption and bioavailability within their population. This is especially true for those with low calcium intake who would benefit the most, including pregnant women (by reducing the risk of preeclampsia) and children (by reducing calcium‐deficiency rickets). Specifically, some animal‐source foods that are naturally high in bioavailable calcium and plant foods that can contribute to calcium intake could be promoted either through policies or educational materials. Some food processing techniques can improve the calcium content in food or increase calcium bioavailability. Staple‐food fortification with calcium can also be a cost‐effective method to increase intake with minimal behavior change required. Lastly, biofortification is currently being investigated to improve calcium content, either through genetic screening and breeding of high‐calcium varieties or through the application of calcium‐rich fertilizers. These mechanisms can be used alone or in combination based on the local context to improve calcium intake within a population.
... The increase of the ash content in FTDs was consistent with the increase of the minerals content. Fungal hyphae are abundant and there are various kinds of metabolic enzymes, which can synthesize phytase, which may degrade phytate phosphorus and phytate mineral complex in TDs, resulting in the increase of the mineral content [43]. Moreover, the mineral content increasing effect of A. niger is better than that of T. koningii. ...
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This study evaluated the ability of Aspergillus niger and Trichoderma koningii to improve the quality of tea dregs (TDs) through solid-state fermentation as well as the value of the fermented tea dregs (FTDs) produced for use as bio-feed additives. After fermentation, FTDs differed in color and structure. Fermentation with A . niger and T . koningii increased the contents of crude protein, crude fiber, neutral detergent fiber, and acid detergent fiber of TDs. Compared to the unfermented group, the contents of reducing sugar, total flavonoids, total polyphenols, and theasaponins were increased in A . niger FTDs, while in T . koningii FTDs caffeine was completely degraded, the theasaponins were lower, and the contents of reducing sugar and caffeine higher. Regarding free amino acids, A . niger FTDs had the highest content of total amino acids, total essential amino acids, total non-essential amino acids, total aromatic amino acids, total branched-chain amino acids, and total non-protein amino acids, and all types of essential amino acids, followed by T . koningii FTDs and the control TDs. Fungal fermentation had similar effects on the content of various hydrolytic amino acids as those on above free amino acids, and increased the content of bitter and umami components. The composition of essential amino acids of TDs or FTDs was similar to that of the standard model, except for sulfur-containing amino acids and isoleucine. Solid-state fermentation with A . niger and T . koningii effectively improved the nutritional value of TDs, increased the contents of functional substances, and improved the flavor of TDs. This study demonstrated a feasible approach to utilize TDs that not only increases animal feed resources, but also reduces the production of resource waste and pollution.
Anemia is a worldwide deficiency that affects women and children. It can be overcome by adding iron in the diet by food fortification. The objective of the study was to improve iron bioavailability in bakery products by adding cumin and inulin. The physicochemical, nutritional and iron bioavailability properties of cumin and inulin fortified bakery products like breads, muffins, cookies and rusk were determined. The ash content analysis of cumin fortified bread was found to have higher mineral content in comparison to the other fortified bakery products. Among all the bakery products cumin fortification with inulin containing bread was found to have second higher iron bioavailability (0.7±0.004 mg/100 g). In the fortified bakery products, bread fortified with cumin and inulin was found to be better than the reference bread. Still in comparison to the reference bread fortified bread, organoleptic was found to be better. Therefore considering the iron bioavailability and relative overall acceptability, cumin fortified bread may be considered as one of the alternative for iron fortified products for preventing the iron deficiency anemia.
We investigated the Fe²⁺ chelating properties and the mechanism of improving Fe²⁺ bioavailability of the Fe²⁺ chelating peptide (GLPGPSGEEGKR, peptide-G-R). Fe²⁺ was chelated with the carboxyl oxygen atom of the Glu-Glu residue in the form of monodentate and bidentate chelating mode. After chelation, peptide-G-R was folded and aggregated to form spherical particles with increasing particle size. Peptide-G-R could increase the Fe²⁺ transport/retention/uptake rate and the relative expression levels of divalent metal transporter 1 (DMT1) in the Caco-2 cells monolayer model. Peptide-G-R could reverse the inhibition of phytic acid on the Fe²⁺ utilization in the Caco-2 cells monolayer model. Molecular dynamics simulation showed that peptide-G-R interacted with DMT1 in the form of intermolecular hydrogen bonds. The transport mechanism of the peptide-G-R-Fe²⁺ complex included endocytosis (main pathway), paracellular pathway (auxiliary way), and DMT1 (potential pathway). Thus, peptide-G-R derived from tilapia skin collagen could be used as a dietary iron supplement.
The chelation process of antioxidant peptides with iron was optimized by response surface methodology with iron chelation percentage as a response. The optimum process was chelation time of 38 min, chelation temperature of 31°C, chelation pH of 5.2, and peptides‐to‐iron mass ratio of 3.4:1. Scanning electron microscopy observation showed the chelate was a smooth and dense granular aggregate morphology. Fourier transform infrared spectroscopy analysis indicated the chelate's characteristic peaks shifted significantly compared with the antioxidant peptides. The α‐helix and random coil contents decreased from the peptides of 60.86% to the chelate of 43.74%. However, the β‐structure contents increased from the peptides of 39.14% to the chelate of 56.26%. The in vitro digestion test suggested the chelate had 97.37% bioaccessibility and 58.53% DPPH radical scavenging effect in gastric digestion. But those in intestinal digestion remained 50.02% and 41.02%, respectively. The chelate can be used as a new iron supplement. The preparation process of wampee seed antioxidant peptides‐iron chelate was optimized by response surface methodology. Iron ions binding to the peptides was through carboxyl oxygen and amino nitrogen atoms. Chelate showed good antioxidant activity and bioaccessibility during gastrointestinal digestion.
Quinoa is a pseudocereal that has gained more attention in the last decades, due to its outstanding nutritional value. Quinoa has a very good protein quality and content, with a complete amino acid profile; it is also rich in minerals and bioactive compounds. However, quinoa, like other cereals and legumes, has phytate which inhibits the absorption of essential minerals. High content of phytate is usually associated with vegetarian diets and diets of rural areas of developing countries. Such diets may lead to mineral deficiencies. Fermentation of quinoa has been shown to be a very effective method for reducing the phytate content and therefore increasing the bioavailability of essential divalent minerals such as iron, calcium and zinc. Fermentation has also been investigated for its effect on improving the antioxidant capacity and content of phenolic compounds, which are considered health-promoting molecules. In addition, this chapter also presents information on the organoleptic changes that occur during quinoa fermentation, which in some cases were shown to be negative. Successful research has been done on the use of dry toasting, either before or after fermentation, to improve the sensory properties of the fermented quinoa. Fermented quinoa, besides having the attributes of being nutritionally adequate, safe and healthy, should also have good sensory properties, which are indispensable for its broad acceptability.
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Phytic acid (PA) is the main phosphorus storage compound in cereals, legumes and oil seeds. In human populations where phytate-rich cereals such as wheat, maize and rice are a staple food, phytate may lead to mineral and trace element deficiency. Zinc appears to be the trace element whose bioavailability is most influenced by PA. Furthermore, several studies in humans as well as in monogastric animals clearly indicate an inhibition of non-haem iron absorption at marginal iron supply due to phytic acid. In fact PA seems to be, at least partly, responsible for the low absorption efficiency and high incidence of iron deficiency anaemia evident in most developing countries, where largely vegetarian diets are consumed. Microbial phytases have provided a realistic means of improving mineral availability from traditionally high-phytate diets. In fact it has been consistently shown that Aspergillus phytases significantly enhance the absorption of calcium, magnesium and zinc in pigs and rats. Furthermore there are a few studies in humans indicating an improvement of iron bioavailability due to microbial phytase. Copyright © 2008 by New Century Health Publishers, LLC. All rights of reproduction in any form reserved.
Iron bioavailability from an infant cereal made of wheat flour with a low extraction rate (70%) and cow milk was measured in infants by using a stable-isotope technique. A dephytinized infant cereal was prepared by adding commercial phytase during manufacture, resulting in degradation of 88% of the native phytic acid. Paired comparisons were made to evaluate the effect of phytic acid on iron bioavailability. Both infant cereals contained identical amounts of ascorbic acid and had a molar ratio of ascorbic acid to iron of 2:1. Iron was added as ferrous sulfate. No difference in iron bioavailability was observed in this study; the geometric mean was 8.7% (range: 3.8–16.9%) and 8.5% (range: 3.4–21.4%) from the cereal with native phytic acid (0.08% phytic acid) and the dephytinized cereal (0.01% phytic acid), respectively. Dephytinization of infant cereals containing a relatively low native phytic acid content and high amounts of ascorbic acid is thus unnecessary to ensure adequate bioavailability of iron.
Conference Paper
Historically, food fortification programs were often undertaken with little attention to issues such as micronutrient bioavailability, optimal levels of addition, or efficacy or to monitoring impact on nutritional status, health, and human function. Several developments in recent years have enabled substantial progress to be made in the design and evaluation of fortification programs. The methodology for estimating the prevalence of inadequate nutrient intakes in a population and tolerable upper intake levels has been established and can be used as the basis for estimating desirable amounts of nutrient addition. More attention is being paid to assessing the bioavailability of nutrients (especially minerals) using stable and radioactive isotopes, and bioavailability of iron compounds can be estimated from changes in total body iron calculated from the ratio of transferrin receptors to serum ferritin. Procedures for quality control of the fortification process have been established. New approaches to monitoring the impact of fortification over time include assessment of liver retinol stores using retinol isotope dilution. In summary, the design and evaluation of food fortification programs now requires a series of formative research procedures on the part of nutritionists, which were not often expected or conducted in the past.
Conference Paper
Comprehensive recommendations for the assessment and control of vitamin A deficiency (VAD) were rigorously reviewed and revised by a working group and presented for discussion at the XX International Vitamin A Consultative Group meeting in Hanoi, Vietnam. These recommendations include standardized definitions of VAD and VAD disorders. VAD is defined as liver stores below 20 mug (0.07 mumol) of retinol per gram. VAD disorders are defined as any health and physiologic consequences attributable to VAD, whether clinically evident (xerophthalmia, anemia, growth retardation, increased infectious morbidity and mortality) or not (impaired iron mobilization, disturbed cellular differentiation and depressed immune response). An estimated 140 million preschool-aged children and at least 7.2 million pregnant women are vitamin A deficient, of whom >10 million suffer clinical complications, principally xerophthalmia but also increased mortality, each year. A maternal history of night blindness during a recent pregnancy was added to the clinical criteria for assessing vitamin A status of a population, and the serum retinol criterion for a "public health problem" was revised to 15% or more of children sampled having levels of <20 mug/dL (0.7 mumol/L). Clinical trials and kinetic models indicate that young children in developing countries cannot achieve normal vitamin A status from plant diets alone. Fortification, supplementation, or other means of increasing vitamin A intake are needed to correct widespread deficiency. To improve the status of young infants, the vitamin A supplements provided to mothers during their first 6 wk postpartum and to young infants during their first 6 mo of life should be doubled.
The Consultation reached consensus on several important issues related to providing additional iron to infants and young children in malaria-endemic areas. The conclusions in this report apply specifically to regions where malaria is endemic. In this report, "iron supplements" refers to medicinal iron supplements given orally to population groups for the prevention and control of iron deficiency. "Iron therapy" refers to medicinal iron supplements given orally or parenterally for treatment of iron deficiency of individual patients. "Iron preparations for home fortification" refers to iron mixed with foods at home. Such iron preparations may be in the form of a powder, crushable tablet, or fat-based spread. "Processed foods fortified with iron" refers to food fortified with iron during food processing.
The effects of different polyphenol-containing beverages on Fe absorption from a bread meal were estimated in adult human subjects from the erythrocyte incorporation of radio-Fe. The test beverages contained different polyphenol structures and were rich in either phenolic acids (chlorogenic acid in coffee), monomeric flavonoids (herb teas, camomile (Matricaria recutita L.), vervain (Verbena officinalis L.), lime flower (Tilia cordata Mill.), pennyroyal (Mentha pulegium L.) and peppermint (Mentha piperita L.), or complex polyphenol polymerization products (black tea and cocoa). All beverages were potent inhibitors of Fe absorption and reduced absorption in a dose-dependent fashion depending on the content of total polyphenols. Compared with a water control meal, beverages containing 20-50 mg total polyphenols/serving reduced Fe absorption from the bread meal by 50-70%, whereas beverages containing 100-400 mg total polyphenols/serving reduced Fe absorption by 60-90%. Inhibition by black tea was 79-94%, peppermint tea 84%, pennyroyal 73%, cocoa 71%, vervain 59%, lime flower 52% and camomile 47%. At an identical concentration of total polyphenols, black tea was more inhibitory than cocoa, and more inhibitory than herb teas camomile, vervain, lime flower and pennyroyal, but was of equal inhibition to peppermint tea. Adding milk to coffee and tea had little or no influence on their inhibitory nature. Our findings demonstrate that herb teas, as well as black tea, coffee and cocoa can be potent inhibitors of Fe absorption. This property should be considered when giving dietary advice in relation to Fe nutrition.