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Heme iron in meat as the main source of iron in the human diet



Iron is a trace element involved in many cardinal metabolic processes of almost all living organisms. It is well known that iron participates in oxygen transport as well as it is a cofactor in many fundamental enzymatic and nonenzymatic processes. Accordingly, disturbances of iron homeostasis can cause serious clinical consequences. In humans, dietary iron can enter the body in two main forms: heme and nonheme. The former is a component of many hemoproteins (including myoglobin, hemoglobin, cytochromes b and c) and is easily absorbed in the duodenal enterocytes. Red meat is an excellent source of heme iron, while the less bioavailable nonheme form is found in large amounts in milk products and vegetables. For this reason, consumers of meat have a better iron status than vegetarians and vegans. Heme iron found in muscle protein should be supplied to humans to prevent iron deficiency, which can lead to anemia. It is easily absorbed and its main source is red meat. In addition, heme iron, which is mainly found in myoglobin in meat, contributes to the desirable bright red color and to the most undesirable brown color of meat. Both heme and nonheme iron are catalysts of lipid oxidation in meat. This process lowers the nutritive value through oxidation of polyunsaturated fatty acids, which produces an undesirable flavor and aroma. The aim of this paper was to discuss the role of heme iron in the human diet.
Buzała M., Słomka A., Janicki B. 2016. Heme iron in meat as the main
source of iron in the human diet. J. Elem., 21(1): 303-314. DOI: 10.5601/
Journal of Elementology ISSN 1644-2296
Mateusz Buzała1, Artur Słomka2, Bogdan Janicki1
1Department of Animal Biochemistry and Biotechnology
UTP University of Science and Technology, Bydgoszcz
2Department of Pathophysiology
Nicolaus Copernicus University in Toruń
Ludwik Rydygier Collegium Medicum in Bydgoszcz
Iron is a trace element involved in many cardinal metabolic processes of almost all living
organisms. It is well known that iron participates in oxygen transport as well as it is a cofactor
in many fundamental enzymatic and nonenzymatic processes. Accordingly, disturbances of iron
homeostasis can cause serious clinical consequences. In humans, dietary iron can enter the body
in two main forms: heme and nonheme. The former is a component of many hemoproteins
(including myoglobin, hemoglobin, cytochromes b and c) and is easily absorbed in the duodenal
enterocytes. Red meat is an excellent source of heme iron, while the less bioavailable nonheme
form is found in large amounts in milk products and vegetables. For this reason, consumers of
meat have a better iron status than vegetarians and vegans. Heme iron found in muscle protein
should be supplied to humans to prevent iron deciency, which can lead to anemia. It is easily
absorbed and its main source is red meat. In addition, heme iron, which is mainly found in my-
oglobin in meat, contributes to the desirable bright red color and to the most undesirable brown
color of meat. Both heme and nonheme iron are catalysts of lipid oxidation in meat. This process
lowers the nutritive value through oxidation of polyunsaturated fatty acids, which produces an
undesirable avor and aroma. The aim of this paper was to discuss the role of heme iron in the
human diet.
Keywords: iron, meat, lipid oxidation, metabolism, meat color.
Mateusz Buzała, MSc, Department of Animal Biochemistry and Biotechnology, UTP University
of Science and Technology, Mazowiecka 28, 85-084 Bydgoszcz, Poland, e-mail:
Iron is crucial for many of the body’s metabolic processes, such as oxygen
transport and storage, and electron transfer. Iron is also necessary for normal
development of the central nervous system, cell proliferation, synthesis and
the repair of genetic material. As a component of catalase and peroxidase,
iron represents a protective mechanism against reactive oxygen species (Mar-
tınez-navarrete et al. 2002, PaPanıkolaoua, PantoPoulos 2005, Mcafee et al.
2010, Słomka et al. 2012). For this reason, prenatal and postanatal iron de-
ciency may affect adversely the cognitive processes and thus lead to neuropsy-
chological disorders (conrad, uMbreıt 2000, taPıero et al. 2001, Mancını,
Hunt 2005). Iron deciency is one of the most common nutritional decien-
cies, affecting around 20% of the world’s population. Deciency of this ele-
ment is more prevalent in less industrialized countries (20-50% of the popula-
tion) than in more developed countries (2-28%) (Martínez-navarrete et al.
2002). The most signicant consequence of iron deciency is sideropenic (iron
deciency) anemia. It is mostly caused by insufcient dietary intake of iron,
often when the demand is high. The disease is most commonly found in in-
fants and in women of childbearing age, often as a result of heavy menstrual
bleeding. It is also stressed that iron deciency can induce many abnorma-
lities in fetal and neonatal development (Słomka et al. 2012). In adolescence
the demand for iron increases, due to the growth and development of muscles
and increasing blood volume. This results in an intensication of erythropoie-
sis, for which iron is necessary to produce myoglobin and hemoglobin (Mesías
et al. 2013). Although iron plays a signicant role in the human body, an ex-
cessive intake of this element may contribute to intestinal mucosal damage
and be a risk factor in cardiovascular diseases, neurodegenerative diseases,
infections and colorectal cancer (Pereıra, vıcente 2013). The results of the
meta-analysis suggest that the intake of heme is associated with an increased
risk of coronary heart disease. In individuals who consume more heme iron a
31% increase in the risk of the disease was found compared with those with
a lower consumption of this type of element (Yang et al. 2014).
The present review is focused on role of heme iron, which is mainly fo-
und in meat and is the principal source of iron in the human diet.
Iron as a component of meat myoglobin
Myoglobin (17 kDa) is the main proteins of muscle tissue sarcoplasm,
containing a centrally located heme (Figure 1), which is a complex of proto-
porphyrin IX with Fe(II). Globin is a single chain of 153 amino acid residues
with 80% of the polypeptide chain existing in a-helical conformations, which
makes protein structure highly compact. Heme in the hydrophobic pocket of
this molecule is protected from oxidation to Fe(III) (brewer 2004, Mancını,
Hunt 2005, PaPanıkolaoua, PantoPoulos 2005). The fth coordination position
of the iron atom is occupied by the imidazole nitrogen atom of histidine resi-
due (His 93). The sixth coordination position of the iron atom on the opposite
side of the heme is the main binding site for oxygen and also for nitric oxide
and carbon oxide. In addition, differences in the occupancy of the sixth coor-
dination position enable myoglobin to exist in three physiological forms. In
deoxymyoglobin, this position remains empty; in oxymyoglobin, it is occupied
by oxygen, and in ferrimyoglobin, the site is occupied by water (brewer 2004,
Mancını, Hunt 2005).
The myoglobin content of skeletal muscles can be inuenced by an ani-
mal’s breed, age and muscle activity (kołczak 2008). Red meat owes its dark
red color to the presence of large amounts of heme, the content of which in
this meat is 10-fold higher than in white meat (bastıde et al. 2011). Beef has
the highest amount of myoglobin per gram of fresh meat (15 mg) compared
to mutton (10 mg), pork (5 mg), poultry and rabbit meat (≤ 5 mg) (valenzu-
ela et al. 2011). Heme iron content in beef may depend on the type of musc-
le, breed and storage time (raMos et al. 2011). Physical activity of animals
may increase the amount of heme iron, especially in muscles having high
oxidative activity. A greater degree of physical tness increases the muscle
oxidative capacity by increasing the number of mitochondria in the white -
bers, hence turning them into red bers (castellını et al. 2002). The muscles
of heifers, young bulls and steers contain less myoglobin than the muscles of
cull cows, while calf muscles have less pigment than steer muscles (kołczak
2008). In addition, the content of total iron, heme iron and myoglobin in the
muscles of animals on low level feeding is higher than in those on high fe-
eding level (PurcHas, busbooM 2005, calkıns, Hodgen 2007). Furthermore,
the above parameters of iron homeostasis are lower in older animals than in
younger ones (calkıns, Hodgen 2007).
Effect of iron on meat color
Meat color is primarily determined by its content of myoglobin, but also
hemoglobin and cytochrome c. The binding of an oxygen molecule to myoglo-
Fig. 1. The structure of heme
bin makes it oxygenated (oxymyoglobin), thus giving the desired bright red
color of meat. During the oxygenation, iron’s valence does not change and the
sixth coordination position is occupied by an oxygen molecule. In addition,
the distal histidine (His 64) in myoglobin interacts with bound oxygen, alte-
ring the oxygen’s structure and stability. As exposure to oxygen increases,
the oxymyoglobin penetrates deeper beneath the meat’s surface. The depth of
oxygen penetration depends on the meat’s temperature, oxygen partial
pressure, pH and competition for oxygen by other processes that require this
cofactor (Mancını, Hunt 2005, kołczak 2008).
Under anaerobic conditions, most often during the vacuum packaging of
meat, oxymyoglobin is converted to deoxymyoglobin, because the sixth coor-
dination position for oxygen is unoccupied and iron is present in the form of
Fe(II). In this case, meat becomes purple red or purple pink, because very
low oxygen partial pressure (<1.4 mm Hg) maintains myoglobin as deoxymy-
oglobin (myoglobin without oxygen).
Metmyoglobin is a molecule between the oxymyoglobin present on the
surface of meat and the deoxymyoglobin present in meat, as a result of a
change in valency of from Fe(II) to Fe(III). Metmyoglobin is formed inside
meat and extends towards the surface, producing the undesirable brown co-
lor of the meat. Metmyoglobin formation depends on many factors, including
oxygen partial pressure, temperature, pH, the reducing activity of meat com-
ponents and in some cases the growth of microorganisms. Metmyoglobin re-
duction is essential to meat color and largely depends on the enzymatic acti-
vity and pool of NADHs (reduced nicotinamide adenine dinucleotide), which
are constantly depleted with the increasing time after slaughter. Lactate
dehydrogenase, which catalyzes the interconversion of pyruvate and lactate
with concomitant interconversion of NADH and NAD+, injected postmortem
into meat was found to oxidize lactate to pyruvate and to reduce the amount
of metmyoglobin, thus improving the color of meat (Mancını, Hunt 2005, k-
czak 2008).
Iron as a catalyst of lipid oxidation in meat
During postmortem changes, the natural antioxidant system that pre-
vents living cells from lipid oxidation becomes increasingly weaker, which
accelerates the lipid oxidation processes. The cessation of blood circulation in
the body shifts metabolism from oxidative to glycolytic during the conversion
of muscle to meat. This results in lactic acid accumulation, which reduces pH
from 7.4 to approx. 6.0-5.5. This is when the structural integrity of muscle
cells is compromised as a result of proteolysis and protein denaturation, re-
leasing iron ions from hemoproteins and low-molecular-weight compounds,
which may become catalysts. Iron initiates lipid oxidation by generating, via
the Fenton reaction, reactive oxygen species capable of abstracting a proton
from unsaturated fatty acids. Free iron ions may bind to negatively charged
phospholipids (such as phosphatidylcholine) in cell membranes and catalyze
the breakdown of pre-formed lipid hydroperoxides. The lipid hydroperoxides
are further decomposed oxidatively to form peroxide radicals or, by reduc-
tion, to produce alkoxyl radicals. These radicals may initiate new chain reac-
tions, and alkoxyl radicals may further decompose to produce aldehydes and
other secondary products of lipid oxidation (carlsen et al. 2005, Mın, aHn
2005, orıno, watanabe 2008). One such short-chain aldehyde is malondialde-
hyde (taPıero et al. 2001, Hęś, korczak 2007, danesHYar 2012). This compo-
und is often used to evaluate the degree of lipid peroxidation and may produce
a rancid avor and aroma, undesirable for the consumer (taPıero et al.
2001, faustMan et al. 2010, danesHYar 2012). Malondialdehyde may induce
DNA damage, leading to mutations, and can react with DNA to form adducts
with deoxyguanosine, deoxyadenosine and deoxycytidine. The major DNA
adduct formed by the reaction of malondialdehyde with DNA is 1,N2-malon-
dialdehyde-deoxyguanosine (M1dG) (bastıde et al. 2011). In addition, heme
proteins that initiate lipid oxidation in biological membranes may impair
membrane function, decrease uidity, inactivate membrane-bound recep-
tors and enzymes, and increase permeability to ions such as Ca2+ (baron,
andersen 2002).
Free iron ions released from heme and ferritin may be considered as the
main catalysts of lipid peroxidation in both raw and cooked meat. Ferritin is
a ubiquitous intracellular protein (consisting of 24 protein subunits) that
stores iron and releases it in a controlled fashion. Ferritin releases iron in
the presence of reducing agents such as superoxide anion and ascorbate
(Mın, aHn 2005). Hydrogen peroxide, present in the muscle cell cytosol, rele-
ases free iron from heme as a result of oxidative cleavage of the porphyrin
ring, whereas ascorbate releases iron ions from ferritin, which catalyzes lipid
peroxidation in meat. Ascorbic acid can exhibit both antioxidant and prooxi-
dant properties, depending on its concentration and the amount of iron pre-
sent. In low concentrations, ascorbic acid most often contributes to lipid pe-
roxidation in muscle tissue by reducing iron, and in high concentrations it
transforms some of peroxide radicals directly into lipid hydroperoxides, as a
result of breaking the free radical reaction by donating a hydrogen atom to
the free radical. Ascorbic acid also regenerates a-tocopherol in biological
membranes (Mın, aHn 2005).
In addition, iron in muscle can be chelated by low-molecular-weight com-
pounds, such as organic phosphate esters, inorganic phosphates, amino acids
and organic acids. Low-molecular-weight, water-soluble iron-chelating agents
may be responsible for catalyzing the oxidation of tissue lipids by iron. What
is more, the conversion of ferritin to hemosiderin in the body is biologically
benecial because it decreases the availability of iron for promotion of lipid
peroxidation. Therefore, the body’s iron metabolism should be strictly regu-
lated by iron-binding proteins to ensure that no free iron exists (Mın, aHn
2005). Ferritin is a ubiquitous and highly conserved iron storage protein,
which plays a major role in iron metabolism by storing iron ions and protec-
ting tissues from its toxic effect. Furthermore, owing to the enzymatic activi-
ty, ferritin molecules are able to oxidize Fe(II) to Fe(III) (orıno, watanabe
2008, Słomka et al. 2012). Non-transferrin-bound iron (NTBI) can be highly
toxic because it facilitates reactive oxygen species generation, which contri-
butes to the damage of all biomolecules. Non-transferrin-bound iron may be
involved in the pathogenesis and progression of many hematological disor-
ders, as well as in the etiopathogenesis of the central nervous system in
neonates, neurodegenerative diseases and diabetes (Słomka et al. 2011, koba
et al. 2013).
The susceptibility of raw meat to lipid oxidation depends on the animal
species, muscle type, activity of antioxidant enzymes, fat content, fatty acid
prole and other factors (Mın et al. 2008). Muscles with a higher number of
red bers (type I or type IIa) are more sensitive to lipid oxidation because
they contain more iron and phospholipids compared to muscles that mostly
contain white bers (faustMan et al. 2010, saMuel et al. 2012). Muscles with
more red bers generate more hydrogen peroxide during auto-oxidation of
this protein compared to meat with a lower content of this pigment. Hydro-
gen peroxide may react with metmyoglobin to form ferrylmyoglobin, which
initiates lipid oxidation by abstracting a hydrogen atom from polyenoic fatty
acids and generates lipid hydroperoxides. Additionally, heating reduces the
activation energy for lipid peroxidation and breaks down initially formed
hydroperoxides to free radicals, which stimulate auto-oxidation processes and
the development of undesirable avor and aroma (Mın et al. 2008). Nonheme
iron plays a greater role in this process, especially in an acidic environment
and in cooked meat. In turn, heme iron may initiate lipid oxidation in both
raw and cooked meat (Hęś, korczak 2007). Additionally, the meat cooking
process inhibits the activity of antioxidant enzymes and releases iron from
heme, leading to its oxygenation.
Source of iron in the human diet
Iron in the human diet has two forms: heme iron (II), which is easily ab-
sorbed, and nonheme iron (III), which is much less readily absorbed by the
body (carPenter, MaHoneY 1992, beard, Han 2009, valenzuela et al. 2009,
scHonfeldt, Hall 2011). Red meat, in particular beef, mutton and goat meat,
is regarded as a richer source of heme iron (Table 1) than poultry meat and
sh (taPıero et al. 2001, uMbreıt 2005, valenzuela et al. 2009, Mcafee et al.
2010, scHonfeldt, Hall 2011, zotte, szendro 2011). Heme iron, although con-
sumed in smaller amounts, is two- or threefold more easily absorbed (50-87%)
than nonheme iron. Nonheme iron, which is found mainly in vegetables and
milk products, forms the majority of all dietary iron (approx. 60%), but its
absorption is low (2-20%) (carPenter, MaHoneY 1992, benıto, Mıller 1998,
valenzuela et al. 2009, 2011). The absorption rate of nonheme iron depends
on the presence of dietary components that increase or inhibit its bioavailabi-
lity (taPıero et al. 2001, uMbreıt 2005, scHonfeldt, Hall 2011, Pereıra et al.
2013). Its absorption is facilitated by factors such as ascorbic acid, citric acid
and some amino acids. Citric acid enhances the absorption of nonheme iron
through chelation, preserving it in the solution of ascorbic acid and some ami-
no acids such as cysteine, which reduce iron to a more readily available form
of Fe(II), thus facilitating its intestinal absorption (carPenter, MaHoneY 1992,
benıto, Mıller 1998, conrad, uMbreıt 2000, uMbreıt 2005, beard, Han 2009,
Pereıra, vıcente 2013). Other organic acids, such as malic and tartaric acid,
can also improve the absorption of iron (lıM et al. 2013). Infants and approx.
one-third of the elderly have low secretion of hydrochloric acid by gastric pa-
rietal cells, which may lead to iron malabsorption (benıto, Mıller 1998). The
absorption of nonheme iron is inhibited by factors such as phosphates, phyta-
tes, dietary ber, lignins, polyphenols and tannins. These inhibitors generally
bind most iron ions into complexes and make them unavailable to transport
proteins. In turn, heme iron, which is easily soluble in the alkaline environ-
ment of the duodenum, is immediately absorbed by enterocytes (conrad,
uMbreıt 2000, 2005, beard, Han 2009). Minerals such as zinc, calcium, copper
and manganese can also inhibit the bioavailability of iron by competing
for the same carrier in enterocytes, modifying the oxidation state of iron or
interfering with metabolism (Mesías et al. 2013). Studies have shown that
calcium chloride also inhibits the absorption of heme iron (lóPez, Martos
2004). As a result, iron in a diet which is high in cereal products and
thus has a substantial bre content will be less bioavailable than in a diet
containing meat, regardless of other factors affecting iron absorption in the
human body (benıto, Mıller 1998, uMbreıt 2005, beard, Han 2009).
Table 1
Iron content in meat of different species of animals
of meat
Iron content
(mg kg-1)Source
Beef 8-220 (Mın et al. 2008, valenzuela et al. 2009, scHonfeldt, Hall 2011,
HoffMann et al. 2010)
Veal 5.5-23 (scHonfeldt, Hall 2011, zotte, szendro 2011)
Mutton 33 (zotte, szendro 2011)
Lamb 9.6-26 (scHonfeldt, Hall 2011, HoffMann et al. 2010)
Goat 21-44 (webb et al. 2005)
Game 33-47 (sales, kotrba 2013, trıuMf et al. 2012)
Pork 5.5-17 (Mın et al. 2008, zotte, szendro 2011, HoffMann et al. 2010)
Poultry 5.9-20 (Mın et al. 2008, zotte, szendro 2011, Buzała et al. 2014)
Rabbit 1-13 (zotte, szendro 2011, cYgan-szczegıelnıak et al. 2012)
Fish 1.2-5 (stanek et al. 2012, grela et al. 2010)
Iron metabolism in the human body – short presentation
The average intake of meat is 41-72 g day-1 in men and 24.2-45.5 g day-1
in women, which supplies the body with 14.5±5 mg and 20.2±28 mg of iron,
respectively (Pereıra, vıcente 2013). Daily dietary iron requirements are
approx. 8 mg for adult men and approx. 18 mg for adult women with men-
strual iron losses (ganz, neMetH 2012). During pregnancy, total iron require-
ment is approx. 1,040 mg (Słomka et al. 2012). However, iron deciency often
occurs in young women in Poland (Hamułka et al. 2011, WaśkieWicz, SygnoW-
ska 2011). Consequences of iron deciency and iron overload in humans are
shown in Figure 2.
Iron is stored mainly in the liver, containing around 60% of the body’s
iron pool, of which around 95% is stored as ferritin in hepatocytes. Small
amounts of iron (around 5%) can also be stored as hemosiderin, apparently a
degradation product of ferritin, which is mainly found in Kupffer cells. The
amount of ferritin, an easily available source of iron, is mainly regulated by
iron regulatory proteins (IRP1 and IRP2). These proteins are key regulators
of iron cell homeostasis in higher eukaryotes. A single ferritin molecule can
hold up to 4,500 iron atoms, which may participate in erythropoiesis. Ery-
Fig. 2. Summary of the consequences of iron deciency and iron overload in human
(koHgo et al. 2008, falkowska, ostrowska 2010, Słomka et al. 2012)
thropoiesis requires around 30 mg of iron/day, and erythrocytes contain aro-
und 80% of the body’s total iron. The remaining content of iron in the body
(around 40%) is found in muscle tissue myoglobin, epithelial reticular cells,
cytochromes and iron-containing enzymes (catalase, peroxidase). Only very
small amounts of iron are excreted and the body’s iron cycle is nearly closed.
A human with around 4 g of iron stored in the body loses only 1 mg per day
(0.025% of the body’s iron) and consumes a similar amount daily with food.
Body iron is lost, among others, through iron found in sloughing epidermal
and intestinal epithelial cells, and as a result of menstrual bleeding in wo-
men (conrad, uMbreıt 2000, taPıero et al. 2001, PaPanıkolaoua, PantoPoulos
2005, uMbreıt 2005, beard, Han 2009, Słomka et al. 2012).
Iron ions in food are absorbed mainly in the duodenum. The transport of
iron ions into enterocytes occurs through the divalent metal transporter
DMT-1, which is located at the apical membrane of intestinal enterocytes.
DMT-1 works in concert with duodenal cytochrome b (Dcytb) (ganz, neMetH
2012). Heme iron passes through the apical membrane of the duodenal ente-
rocytes with the help of the heme transporter HCP1 protein (heme carrier
protein 1). Next, heme is released from the porphyrin ring by the action of
the heme oxygenase enzyme and divalent iron is released. The porphyrin
ring may be responsible for the high absorption of heme iron (lóPez, Martos
2004). In turn, globin degradation metabolites facilitate the absorption of
nonheme iron. Next, iron leaves the cell through the basolateral membrane
of the enterocyte and enters the bloodstream via ferroportin, which works in
combination with hephaestin. Ferroportin is a key iron transporter found on
duodenal enterocytes. It is also subject to molecular control. After binding to
hepcidin, ferroportin decreases the export of iron from cells to the blood.
Hepcidin is a peptide hormone that inhibits duodenal iron absorption and its
synthesis is regulated by iron. Large amounts of iron in the hepatocytes
(inammation) contribute to higher hepcidin production in the liver, thus
reducing iron absorption and release in the body. In turn, iron deciency
decreases or inhibits hepcidin production by hepatocytes, allowing more iron
to enter blood plasma (lóPez, Martos 2004, ganz, neMetH 2012). Following
release from enterocytes, the ferrooxidase enzymes hephaestin and cerulopla-
smin, which contain atoms of copper, can oxidize Fe(II) to Fe(III). In the
blood, two atoms of oxidized iron bind to transferrin, which is a 78 kDa gly-
coprotein. This protein is responsible for transporting iron to most cells and
normally about 25-30% of transferrin is saturated by iron. The transferrin-
-Fe(III) complex in blood is taken up by transferrin receptors (TfR1 and
TfR2) located in the target cell membrane. The rate and site of iron uptake
from plasma depends on the number of transferrin receptors, which are hi-
ghly expressed in all diving cells, especially erythroid cells. Transferrin re-
ceptor 1 binds two molecules of transferrin, as a result of which iron ions are
released into the cell cytoplasm. The role of the second receptor (TfR2)
in iron metabolism has received less attention. Probably, this receptor is
responsible for binding non-transferrin-bound iron (NTBI). Iron ions are
transported into the cell via endocytosis. In the resulting endosome, which
maintains an acidic pH, iron is separated from transferrin. Next, iron enters
the cytoplasm via DMT-1 present in the endosome membrane. Iron ions in
the cytosol are incorporated into ferritin and hemosiderin to form a storage
pool or are used for producing heme and nonheme proteins. After release of
iron, apotransferrin is recycled to the membrane, leaves the cell and enters
circulation to transport the next iron ions again (benıto, Mıller 1998, con-
rad, uMbreıt 2000, taPıero et al. 2001, uMbreıt 2005, beard, Han 2009,
Słomka et al. 2012).
Heme iron found in muscle protein should be supplied to humans to pre-
vent iron deciency, which can lead to anemia. Heme iron, whose main sour-
ce is red meat, is easily absorbed by the human body. In addition, heme iron,
which is mainly found in myoglobin in meat, contributes to the desirable
bright red color and to the most undesirable brown color of meat. Both heme
and nonheme iron are catalysts of lipid oxidation in meat. This process lo-
wers the nutritive value through oxidation of polyunsaturated fatty acids,
which produces an undesirable avor and aroma.
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... colorectal cancer (CRC), negative environmental effects, and non-sustainable land use issues (Bertolotti, Carfora, & Catellani, 2020). Regarding the former, heme-proteins and their capacity to stimulate lipid oxidation is hypothesized to be one of the risk factors, while these proteins at the same time are nutritionally important since heme iron has significantly higher bioavailability compared with nonheme iron (Buzala, Slomka, & Janicki, 2016). Substituting red meat by fish protein has been found to lower the risks of CRC as well as cardiovascular disease and all-cause mortality, based e.g. on a study that tracked 29,682 men and women for up to 30 years (Zhong et al., 2020). ...
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The degradation of trout and bovine hemoglobin (Hb) and their pro-oxidant activities in washed cod muscle mince (WCM) were studied using simple pH-shifts to simulate gastrointestinal (GI) conditions (pH 7→6→3→7), as well as full static in vitro GI digestion. Following gastric acidification to pH 6, metHb formation increased, especially for trout Hb. Subsequent acidification to pH 3 promoted Hb unfolding and partial or complete heme group-loss. During full GI digestion, polypeptide/peptide analyses revealed more extensive Hb-degradation in the gastric than duodenal phase, without any species-differences. When digesting WCM +/-Hb, both Hbs strongly promoted malondialdehyde (MDA), 4-hydroxy-2-hexenal (HHE), and 4-hydroxy-2-nonenal (HNE) formation, peaking at the end of the gastric phase. Trout-Hb stimulated MDA and HHE more than bovine Hb in gastric phase 1. Altogether, partially degraded Hb, and/or free hemin -both mammal and fish-derived- stimulated oxidation of PUFA-rich lipids under GI-conditions, especially gastric ones.
... Meat in the human diet is a source of wholesome, easily digestible proteins, highenergy fat, vitamins-especially from the B group, as well as micronutrients necessary in metabolic processes in the human body [1]. The bioavailability of selected ingredients in meat is much higher than in food of plant origin [2,3]. ...
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Social pressure on increased protection and welfare of animals results mainly from the initiative of people living in the urbanized parts of the world. The respect for the right to freedom of religion, which is indisputably one of the fundamental liberal rights, must be taken into account. The right to freedom to religion also includes the right to follow a religion’s dietary recommendations. The aim of the literature analysis was to systematize the knowledge on the ethical aspects and quality of meat obtained from carcasses of animals subjected to conventional and ritual slaughter. Consistent with the importance of ritual slaughter for humans of two major faiths (Islam and Judaism), it is important that scientists be objective when evaluating these practices from an animal welfare and meat quality point of view. To evaluate the welfare of the slaughtered animal, it is necessary to openly discuss ritual slaughter and the improvement of its methods. The quality of meat and the degree of bleeding of animals do not always correlate with the ritual slaughter method used.
... In line with our finding, a recent multi-country study suggested that very low intake of saturated fat (less than 7% of energy) might have an adverse effect on mortality [32]. In addition, animal proteins are rich in iron, and low iron intake is associated with anemia [33], which is a risk factor for CVD [34]. In contrast, excessive dietary iron intake is associated with increased risk of coronary heart disease [35]. ...
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Background Evidence is limited regarding the association between low-carbohydrate diet (LCD) score and mortality among Asians, a population that consumes a large amount of carbohydrates. Objective The present study examined the association between low-carbohydrate diet (LCD) score (based on percentage of energy as carbohydrate, fat, and protein) and the risk of total and cause-specific mortality among Asians. Design This study was a prospective cohort study in Japan with follow-up for a median of 16.9 years involving 43008 men and 50646 women aged 45–75 years. Association of LCD score, LCD score based on animal sources of protein and fat, and LCD score based on plant sources of protein and fat with risk of mortality was assessed using Cox proportional hazards model. Results A U-shaped association was observed between LCD score and total mortality: the multivariable-adjusted hazard ratios (HRs) (95% CI) of total mortality for lowest through highest scores were 1.00, 0.95 (0.91, 1.01), 0.93 (0.88, 0.98), 0.93 (0.88, 0.98), and 1.01 (0.95, 1.07) (P-non-linearity <0.01). A similar association was found for mortality from cardiovascular disease (CVD) and heart disease. LCD score based on carbohydrate, animal protein, and animal fat also showed a U-shaped association for total mortality (P-non-linearity <0.01). In contrast, LCD score based on carbohydrate, plant protein, and plant fat was linearly associated with lower total (HR, 0.89; 95% CI: 0.83, 0.94 for highest versus lowest quintile), CVD [0.82 (0.73, 0.92)], heart disease [0.83 (0.71, 0.98)], and cerebrovascular disease [0.75 (0.62, 0.91) mortality. Conclusions Both LCD with high animal protein and fat and high-carbohydrate diet with low animal protein and fat were associated with higher risk of mortality. Meanwhile, LCD high in plant-based sources of protein and fat was associated with a lower risk of total and CVD mortality.
The studies aimed to verify the effect of Cu, Zn and Fe glycine chelate on the antioxidative status in the thigh meat of broiler chickens. The study assumption was that due to the antioxidative or prooxidative effect of Cu, Zn and Fe, these elements supplemented to chickens in an easily assimilable form would modify the antioxidative status of meat and those having a prooxidative effect could deteriorate the quality of meat. The experiment involved three hundred and fifty Ross 308 chickens divided into seven equipotent experimental groups. Over 42 days of the experiment, the chickens were administered Cu, Zn and Fe glycine chelates in an amount corresponding to 50% of the requirement (experimental factor I) or 25% of the requirement (experimental factor II). The level of oxidative stress indicators such as superoxide dismutase, catalase, glutathione, glutathione peroxidase and malondialdehyde was determined in the muscles and blood. The groups receiving Zn or Cu chelate showed statistically confirmed higher activity of superoxide dismutase, catalase, and a higher level of glutathione in comparison to the group receiving Fe chelate. In order to increase the antioxidative stability of thigh meat, it is sufficient that broiler chickens receive Zn or Cu in the form of glycine chelate in an amount covering 25% of their requirement of such minerals. On the other hand, the use of Fe glycine chelates decreased antioxidative stability due to an increase in the level of malondialdehyde, so it should be considered whether the administration of pro-oxidative Fe chelate to broilers is advisable.
This chapter gives an overall introduction of food pigments including their roles in the food industry, coloring mechanisms behind their chemical nature and their classification. Based on the chemical structures, some important and common natural pigments are illustrated according to their chemical molecules, changes and treatments during food processing, and related protective techniques including heme, chlorophylls, carotenoids and flavonoids with anthocyanins, catechins and tannins emphasized. In this chapter, plenty of detailed information about surrounding environmental effects on the changes of pigment molecules and the related color is provided to help readers understand the reaction mechanisms and to associate them with food processing techniques such as acid/alkaline treatment, modified atmospheric package and heat treatment.
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Meat from food animals is an important and long established dietary source of protein and essential nutrients. Many studies consistently reported that red and white meat can act as an important source of nutrients like iron, zinc, selenium and vitamin B12. However, various reports have also confirmed a positive correlation between meat consumption and the risk of cardiovascular disease and colon cancer, which led to a negative perception of the role of animal protein source in health. The aim of this review is to highlight on existing literature on risks and benefits of meat consumption, focusing on anxieties, myths, concerns and accurate facts. While we investigate many such reports about the correlation between meat consumption and the risk of such diseses, we could identify several methodological limitations and inconsistencies, which may affect the validity of their research findings. There is no well-built report or study to support the recent conclusion from the World Cancer Research Fund (WCRF) about red meat and its suspected role in colon cancer. Several cohort studies indicated the role of lean meat as positive moderator of lipid profiles as well as dietary source of anti-inflammatory long chain (LC) ω3 PUFAs and conjugated linoleic acid (CLA). In conclusion, moderate level of meat consumption as part of a balanced diet is unlikely to increase risk for cardiovascular disease or colorectal cancer, but may unquestionably influence nutrient bioavailability and fatty acid profiles, thereby positively lead to better health benefits. Keywords: Meat consumption, red meat, conjugated linoleic acid, meat nutrients
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Iron is one of the most important micronutrients for crop plants due to its use in important physiological processes such as photosynthesis, mitochondrial respiration, metal homeostasis, and chlorophyll synthesis. Crop plants have adapted different strategies for uptake, transport, accumulation, and storage of iron in tissues and organs which later can be consumed by humans. Estimates indicate that about 2 billion people (33% of human population) are at risk of iron deficiency in which infants, children, and pregnant women are potentially compromised. Biofortification refers to the increase in concentration of micronutrients in edible parts of plants and understanding the pathways for iron accumulation in plants is necessary for breeding iron‐enriched crops. Iron‐biofortified crops are also one of the key factors in achieving multiple United Nations Sustainable Development goals. This review article covers different strategies of iron acquisition and transport in plants, its bioavailability, coping with the iron deficiency as a global perspective, the current status of iron biofortification, and how breeding future biofortified crops could be helpful in combating the said issue in a sustainable manner.
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The study assessed the stability for fresh beef patties with the inclusion of clove extract (CE) as a natural antioxidant in comparison to butylated hydroxytoluene (BHT) and ascorbic acid (AA) at frozen storage. Four different patties were made dependent on the added antioxidants: control (added no antioxidants), added with 0.02% BHT, 0.05% AA, and 0.1% CE. Inclusion of BHT, AA, and CE resulted in a significant reduction of thiobarbituric acid reactive substances (TBARS) and hue angle (h°) value and increase of redness (CIE a*) and chroma (C*) values (p<0.05). BHT, AA, and CE were observed effectively to retard lipid oxidation and increase color stability. BHT and AA revealed significantly (p<0.05) higher thiol content than the control and CE. However, the reduction percentage for thiol content in CE treated patties was lower than the control and AA-treated patties from first to last time of storage. Moreover, inclusion of AA and CE led to significantly (p<0.05) increased heme iron content when compared to BHT and the control. In conclusion, CE can replace the application of AA and BHT while improving lipid stability, heme iron content, and color stableness of fresh beef patties throughout frozen storage.
Iodine, selenium and iron are micronutrients essential for thyroid hormone synthesis causing their low plasma levels an additional risk of autoimmune thyroid diseases. A Portuguese TDS pilot study representative of diets in Portugal was carried out, since foods are the main natural sources of these micronutrients. Six hundred and twenty-four samples were collected based on local markets and later analysed in pools of ten meat samples, twenty-seven fish, nine chicken eggs and six cow dairy products. The iodine and selenium contents were determined using ICP-MS after alkaline (iodine) or acid digestion (selenium) and iron by ICP-OES after acid digestion. The highest content of three oligoelements was detected in fish. Meat had lower iodine content and the dairy products lower selenium and iron levels. Sardine presented significant different levels in summer and winter for iodine, and in summer and autumn for selenium, mackerel had diverse contents of iron in summer and autumn. The contribution of salmon and milk for iodine RNI was around 40%, for children and adults. Shrimp is also the food with more selenium, exceeding 1.5 times the % RNI for children and adults females, while iron maximum contribution was observed in meat for children and adult males.
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Because the production of oat geese in Poland, destined mostly for markets of Western Europe, has increased, there is a need for a review on the performance traits of these geese and on the quality of their meat and fat. Goose production is based on a genotype of Italian geese brought to Poland in 1962 and selected for improving their reproduction and meat traits. Currently the population of geese, their reproduction and the commercial birds derived from them, are referred to as White Kołudzka® geese. Selection of these birds is based on a programme based on genetic improvement of strains W11 (reproduction traits) and W33 (meat traits). The programme’s aim is not only to enhance breeding and the performance value of these strains, but to produce, as a result of cross breeding, good quality of meat and fat in the form of the crossbred W31, and thus to produce oat geese that meet today’s market requirements. Poland is one of the largest goose producers in Europe. Goose meat and fat show high nutritional quality due to the specific nutrition and conditions in which the geese are kept, i.e. in open-air runs and at pasture. Recently, goose meat has become increasingly popular and has attracted much consumer interest. This increase in demand requires more knowledge about the meat’s nutritional value. Polish oat geese are reared up to 14 weeks of age, then fattened freely with oats up to the 17th week of age. Fattening with oats results in good quality meat and fat, with excellent sensory properties. The following paper reviews the rearing systems, slaughter value and quality of meat and fat of White Kołudzka® geese kept under semi-intensive systems.
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This review compares iron and zinc food sources, dietary intakes, dietary recommendations, nutritional status, bioavailability and interactions, with a focus on adults in economically-developed countries. The main sources of iron and zinc are cereals and meat, with fortificant iron and zinc potentially making an important contribution. Current fortification practices are concerning as there is little regulation or monitoring of intakes. In the countries included in this review, the proportion of individuals with iron intakes below recommendations was similar to the proportion of individuals with suboptimal iron status. Due to a lack of population zinc status information, similar comparisons cannot be made for zinc intakes and status. Significant data indicate that inhibitors of iron absorption include phytate, polyphenols, soy protein and calcium, and enhancers include animal tissue and ascorbic acid. It appears that of these, only phytate and soy protein also inhibit zinc absorption. Most data are derived from single-meal studies, which tend to amplify impacts on iron absorption in contrast to studies that utilize a realistic food matrix. These interactions need to be substantiated by studies that account for whole diets, however in the interim, it may be prudent for those at risk of iron deficiency to maximize absorption by reducing consumption of inhibitors and including enhancers at mealtimes.
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Iron deficiency is the most common and widespread nutritional disorder in the world. Consuming foods rich in dietary iron (high in both content and availability) is an effective way to alleviate iron deficiency. Iron from animal foods is more bio-available than iron from plant sources. This is due to the heme iron content in animal foods. According to the Monsen model, an average of 40% of total iron in meat, fish and poultry is in the heme form. Although the Monsen model can provide a generally good estimate of the heme iron content in animal products, recent research has suggested that the constant 40% value of heme iron is either an under- or over-estimation, depending on the source of the food. During this study a review was performed on the heme iron content of meat, fish and poultry, and comparisons are made with reference to the Monsen model. The aim of this study was to investigate whether using the constant 40% value for heme iron is adequate in describing the bio-availability of total iron in a particular food.
Four species of freshwater fish were included into the research project, namely: pike (Esox lucius L.), zander (Sander lucioperca L.), carp (Cyprinus carpio L.), and bream (Aramis brama L.). Six fish of each species were fished every month from September to November 2007. Morphometric features of fish were assessed as was the content of nutrients and mineral components. Furthermore, a profile of fatty acids was analysed. The content of nutrients in fish depended on the fishing period and its level diminished during the consecutive months of fishing. The highest amount of saturated fatty acids was determined in the fat of bream and pike flesh. The flesh of carp had the lowest level of polyunsaturated fatty acids, whereas the flesh of pike and zander - the highest. From the nutritional point of view, the flesh of pike and zander was characterized by the most beneficial n-3 to n-6 fatty acids ratio. The highest level of EPA was found in the lipids derived from bream and pike, and the fat from pike and zander flesh had the highest level of DHA. The content of heavy metals did not exceed the permissible levels as pointed in relevant standards, and no significant differences depending on the fishing period were found.
The aim of this work was to analyse the concentrations of selected some elements such as sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe) and zinc (Zn) in the water, muscle tissue and gills of perch sampled in autumn from Lake Gopło in NW Poland. The correlations between the fish size (body length) and metal concentrations in the tissues were investigated by the linear regression analysis. In addition, the bioaccumulation coefficient, as a measure of accumulation intensity of an element in an organ was analysed. The mean content of K, Mg and Zn in the analysed perch was higher in the muscle (18.90, 1.53 and 52.92 mg×kg-1) than in gills (8.88, 1.30 and 44.99 mg×kg-1) and the difference between these values (except for Zn) was statistically significant (p 0.05). The analyses of the correlation between metal concentration in the meat and the body length of fish show that the bioaccumulation of Na, K, Mg and Zn decreases as the fish body length increases (negative correlation). The evaluation of the chemical pollution of Lake Gopło concentrations was based on the following ions (N-NO3, N-NO2 and P-PO4) and minerals (Na, K, Ca, Mg and Zn). The concentrations of nitrite nitrogen in the waters of Lake Gopło range from 0.012 (in September) to 0.057 mg N-NO2 dm-3 (in November). The concentration of nitrate nitrogen ranges from 0.09 to 1.888 mg N-NO3 dm-3. The concentration of orthophosphate in surface waters of Lake Gopło is not very diverse (0.17 – 0.2 mg PO4-3 dm-3).
Iron is a mineral that is necessary for producing red blood cells and for redox processes. Iron deficiency is considered to be the commonest worldwide nutritional deficiency and affects approximately 20% of the world population. Lack of iron may lead to unusual tiredness, shortness of breath, a decrease in physical performance, and learning problems in children and adults, and may increase your chance of getting an infection. This deficiency is partly induced by plant-based diets, containing low levels of poorly bio-available iron. The most effective technological approaches to combat iron deficiency in developing countries include supplementation targeted to high risk groups combined with a program of food fortification and dietary strategies designed to maximize the bio-availability of both the added and the intrinsic food iron. In this paper, different aspects related to iron-fortified foods is reviewed. These include used iron compounds, considering its bioavailability and organoleptic problems, food vehicles and possible interactions.
Adolescence is an important period of nutritional vulnerability due to increased dietary requirements for growth and development. Iron needs are elevated as a result of intensive growth and muscular development, which implies an increase in blood volume; thus, it is extremely important for the adolescent's iron requirements to be met. Diet, therefore, must provide enough iron and, moreover, nutrients producing adequate iron bioavailability to favor element utilization and thus be sufficient for needs at this stage of life. Currently, many adolescents consume monotonous and unbalanced diets which may limit mineral intake and/or bioavailability, leading to iron deficiency and, consequently, to ferropenic anemia, a nutritional deficit of worldwide prevalence. Iron deficiency, apart from provoking important physiological repercussions, can adversely affect adolescents' cognitive ability and behavior. Accordingly, promoting the consumption of a varied, adjusted, and balanced diet by adolescents will facilitate iron utilization, benefiting their health both at present and in adulthood. This review discusses how physiological changes during adolescence can cause iron requirements to increase. Consequently, it is important that diet should contribute an appropriate amount of this mineral and, moreover, with an adequate bioavailability to satisfy needs during this special period of life.
Goat meat has been established as lean meat with favourable nutritional quality. Its attributes are concordant with present day consumer demands for leaner and nutritious meat, and hence should be the basis for promoting the meat. Sensory evaluations have shown that goat meat is acceptably palatable and desirable to consumers. The meat may be as acceptable as mutton if animals of similar ages are compared. However, goat meat tends to be less tender and less juicy than sheep meat because of some possible mitigating factors that are discussed. Goat meat has a species-specific flavour and aroma, which differ from that of sheep meat. In terms of appearance, goat meat tends to have a slightly lower a* value than had been reported for sheep meat, but indications are that the colour is acceptable to consumers. The meat tends to have a high ultimate pH, a fact that is at least partly attributed to stressful peri-mortem handling and the related effects on glycogen metabolism. Goat carcasses are less compact and leaner than those of sheep. This has implications on the proportions of primal cuts, separable tissues within the carcass as well as carcass chilling, which affects the quality of the meat. Recommendations have thus been made about the post-mortem handling of goat carcasses, carcass grading/classification systems and that carcass jointing be cognisant of these factors.
Purpose: Heme iron may contribute to the development of atherosclerosis by catalyzing production of hydroxyl-free radicals and promoting low-density lipoprotein oxidation. However, epidemiologic findings regarding the association between heme iron intake and risk of coronary heart disease (CHD) are inconsistent. We aimed to investigate the association by carrying out a meta-analysis of prospective studies. Methods: Relevant studies were identified by using PubMed and EMBASE databases between January 1966 and April 2013 and also by manually reviewing the reference lists of retrieved publications. Summary relative risks (RRs) with corresponding 95% confidence intervals (CIs) were computed using a random-effects model. Results: Six prospective studies, which contained a total of 131,553 participants and 2,459 CHD cases, met the inclusion criteria. Combined results indicated that participants with higher heme iron intake had a 31% increased risk of CHD, compared with those with lower intake (RR = 1.31, 95% CI 1.04-1.67), with significant heterogeneity (P(heterogeneity) = 0.05, I(2) = 55.0%). Excluding the only study from Japan (limiting to Western studies) yielded a RR of 1.46 (95% CI 1.21-1.76), with no study heterogeneity (P(heterogeneity) = 0.44, I(2) = 0.0%). The dose-response RR of CHD for an increase in heme iron intake of 1 mg/day was 1.27 (95% CI 1.10-1.47), with low heterogeneity (P (heterogeneity) = 0.25, I (2) = 25.8%). We observed no significant publication bias. Conclusions: This meta-analysis suggests that heme iron intake was associated with an increased risk of CHD.