557
and hydroperoxides which induce cell death and tissue atrophy (Mairrino et al.
1991). Another group of selenoproteins are the iodothyronine deiodinases essential
for the conversion of thyrocin or tetraiodothyronine (T4) to its physiologically
active form tri–iodothyronine (T3) (Arthur 1997). Keshan disease linked to coxasackie B virus and dietary deficiency of selenium was named after Keshan county of
China. The primary symptoms of Keshan disease is myocardial necrosis leading to
weakening of heart. Another major disease caused by Se is Kaschin–Beck is bone
and joint disease referred to as osteoarthropathy which occurs in children of China
and in Southeast Siberia (Ge and Yang 1993; Li et al. 1984) areas where the availability of soil selenium for crop growth is low (Khokhar et al. 2012). Acidic soils
high in organic matter and iron oxide content appear to be responsible for fixing
selenium in the forms that are poorly absorbed by staple crops for example cereal
grains, typically have a selenium content of less than 0.01ug/g (Johnson et al. 1996).
Best natural sources of Se include Brazil nuts, fish, whole grain cereals, pork, ham,
chicken, cheese, and eggs, mushrooms, lentils, spinach, milk, banana etc.
Zinc Zinc is required for proper growth and maintenance of human body and
working of the body’s immune system. It plays a vital role in cell division, cell
growth, wound healing, and breakdown of carbohydrates. It is distributed widely in
plant and animal tissues and occurs in all living cells. It is required for the structure
and activity of more than 300 enzymes from many species. The significance of zinc
is reflected by the numerous functions and activities over which it exerts a regulatory role (Falchuk 1993; Lukaski 2004; Vallee and Falchuk 1993). It is required in
the synthesis of nucleic acid and protein, cellular differentiation and replication, and
glucose use and insulin secretion. It exerts regulatory actions in the production, storage, and secretion of hormones and regulating interactions between hormones and
receptors and end–organ responsiveness. Adequate zinc is needed for the integration
of many physiologic functions in the body such as immunity, reproduction, taste,
skeletal development, behavior, and gastrointestinal function. Carbonic anhydrase,
a zinc metalloprotein (Falchuk 1993; Vallee and Falchuk 1993) that regulates the
elimination of carbon dioxide from cells, may play a role in facilitating performance. Natural food sources of zinc include oysters, red meat, poultry, beans, nuts,
whole grains, pumpkin seed and sunflower seeds. Certain herbs like alfalfa, burdock
root, cayenne, chamomile, chickweed, dandelion, eyebright, fennel seed, hops, milk
thistle, mullein, nettle, parsley, rose hips, sage, sarsaparilla, skullcap, and wild yam
are also considered as good source of zinc (Lukaski 2004; Gibney et al. 2009).
Chromium Chromium is an essential nutrient required for carbohydrate and fat
metabolism. It has been found to potentiate the action of insulin at the cellular level
(Lukaski 1999). The mechanism involves various enzymatic changes including
insulin binding to its membrane receptor which results in an intermolecular phosphorylation cascade leading to increased insulin sensitivity (Vincent 2000).
Physiologically active forms of chromium facilitate insulin action, which results in
a decreased need for insulin (Anderson 1997; Mertz 1993). The perception that the
general public may consume diets low in chromium (Anderson and Kozlovsky
25 Bioavailability of Nutrients and Safety Measurements
and hydroperoxides which induce cell death and tissue atrophy (Mairrino et al.
1991). Another group of selenoproteins are the iodothyronine deiodinases essential
for the conversion of thyrocin or tetraiodothyronine (T4) to its physiologically
active form tri–iodothyronine (T3) (Arthur 1997). Keshan disease linked to coxasackie B virus and dietary deficiency of selenium was named after Keshan county of
China. The primary symptoms of Keshan disease is myocardial necrosis leading to
weakening of heart. Another major disease caused by Se is Kaschin–Beck is bone
and joint disease referred to as osteoarthropathy which occurs in children of China
and in Southeast Siberia (Ge and Yang 1993; Li et al. 1984) areas where the availability of soil selenium for crop growth is low (Khokhar et al. 2012). Acidic soils
high in organic matter and iron oxide content appear to be responsible for fixing
selenium in the forms that are poorly absorbed by staple crops for example cereal
grains, typically have a selenium content of less than 0.01ug/g (Johnson et al. 1996).
Best natural sources of Se include Brazil nuts, fish, whole grain cereals, pork, ham,
chicken, cheese, and eggs, mushrooms, lentils, spinach, milk, banana etc.
Zinc Zinc is required for proper growth and maintenance of human body and
working of the body’s immune system. It plays a vital role in cell division, cell
growth, wound healing, and breakdown of carbohydrates. It is distributed widely in
plant and animal tissues and occurs in all living cells. It is required for the structure
and activity of more than 300 enzymes from many species. The significance of zinc
is reflected by the numerous functions and activities over which it exerts a regulatory role (Falchuk 1993; Lukaski 2004; Vallee and Falchuk 1993). It is required in
the synthesis of nucleic acid and protein, cellular differentiation and replication, and
glucose use and insulin secretion. It exerts regulatory actions in the production, storage, and secretion of hormones and regulating interactions between hormones and
receptors and end–organ responsiveness. Adequate zinc is needed for the integration
of many physiologic functions in the body such as immunity, reproduction, taste,
skeletal development, behavior, and gastrointestinal function. Carbonic anhydrase,
a zinc metalloprotein (Falchuk 1993; Vallee and Falchuk 1993) that regulates the
elimination of carbon dioxide from cells, may play a role in facilitating performance. Natural food sources of zinc include oysters, red meat, poultry, beans, nuts,
whole grains, pumpkin seed and sunflower seeds. Certain herbs like alfalfa, burdock
root, cayenne, chamomile, chickweed, dandelion, eyebright, fennel seed, hops, milk
thistle, mullein, nettle, parsley, rose hips, sage, sarsaparilla, skullcap, and wild yam
are also considered as good source of zinc (Lukaski 2004; Gibney et al. 2009).
Chromium Chromium is an essential nutrient required for carbohydrate and fat
metabolism. It has been found to potentiate the action of insulin at the cellular level
(Lukaski 1999). The mechanism involves various enzymatic changes including
insulin binding to its membrane receptor which results in an intermolecular phosphorylation cascade leading to increased insulin sensitivity (Vincent 2000).
Physiologically active forms of chromium facilitate insulin action, which results in
a decreased need for insulin (Anderson 1997; Mertz 1993). The perception that the
general public may consume diets low in chromium (Anderson and Kozlovsky
25 Bioavailability of Nutrients and Safety Measurements