Micro elements
The
micro elements which are essential for normal body functions are Iron(Fe),
Copper(Cu), Iodine(I), Fluorine(F), Zinc(Zn), Cobalt(Co), Manganese(Mn),
Chromium(Cr), Molybdenum(Mo) and Selenium(Se).
Iron is
one of the most essential micro elements in the body. It plays a vital role in
many oxidation-reduction reactions. Hemoglobin and cytochromes contain Iron in
them.
·
Iron is involved in the transport of oxygen by hemoglobin.
·
Iron is essential for synthesis of cytochromes, a component of electron
transport chain.
·
Myoglobin is an iron containing protein similar to hemoglobin and is
present in muscle tissue.
·
Succinate dehydrogenase requires iron as a co-factor.
·
Iron improves immune status.
Meat,
fish, liver are rich sources of iron.
Cereals, nuts, spinach, dates are good plant sources of iron.
Normally,
about 5 to 10% of dietary iron is absorbed by the active transport
process.
Most absorption occurs in the duodenum. Infants and children absorb a
higher
percentage of iron from food than adults. Iron
deficient children absorb
twice as
much as that of normal children. Excess dietary iron is stored as ferritin.
Only
lesser amounts are excreted in the urine, feces and sweat.
· Impaired iron absorption takes place in patients who have total
removal of stomach or a removal of the considerable amount of the intestine.
· A diet high in phosphate causes decreased absorption due to the
formation of insoluble ferric phosphate.
· Copper deficiency reduces iron absorption, as copper helps in
transport of iron.
· Phytic acid and oxalic acid interfere with iron absorption.
· Vitamin C increases iron absorption.
Deficiency of iron causes iron
deficiency anemia. The deficiency may be due to dietary or lack of iron
absorption due to gastro intestinal tract diseases like diarrhoea.
Copper is an essential micro element.
Copper content in an adult human is about 100 mg. Copper in whole blood is
almost evenly distributed between cell and plasma. The highest concentrations
are found in liver and kidney.
·
Copper forms integral part of certain enzymes like cytochrome oxidase
and catalase.
·
Ceruloplasmin a copper containing protein is required for iron
absorption.
·
Superoxide dismutase (SOD) contains copper ion, SOD converts super oxide
radicals to hydrogen peroxide.
·
It is also present in cytochrome C, which is involved in electron
transport in mitochondria.
·
Copper is also needed for bone formation as well as for the maintenance
of myelin within the nervous system.
·
Copper helps to form insoluble elastin fibres by cross-linking soluble
pro-elastin.
Copper is present in many foods and
the best sources are meat, nuts, legumes and cereals.
Absorption of copper into the blood
stream occurs via the villi of the small intestine. About 30 percent of the
dietary copper is absorbed in the duodenum. Only 10 - 60 μg of copper is
excreted in normal urine in 24 hours.
· A diet deficient in copper causes loss of weight.
· Copper deficiency produces microcytic hypochromic
anemia.Elastin formation is impaired in copper deficiency.
· Copper deficiency turns hair grey, which however,
can be controlled by administration of copper.
· Deficiency of copper is sometimes associated with decrease in
taste sensitivity, which is restored by oral administration of copper.
The adult human body contains about
50 mg of organically bound iodine. Nearly half of this is present in muscles.
Most of the body iodine is present in the thyroid gland, but all cells contain
traces of iodine.
The thyroid gland is chiefly
concerned with the uptake of iodine for the synthesis of the thyroid hormones,
tetra Iodothyronine(Thyroxin T4) and tri Iodothyronine(T3) which influence a
large number of metabolic functions. These iodine containing hormones regulate
energy metabolism, synthesis of proteins and cholesterol and also in the
conversion of carotene to vitamin A.
Sea
water is rich source ofIodine. Vegetables grown in Iodine-rich soil will
naturally be the good sources of iodine. Animal sources of iodine include milk,
sea fish and crabs.
Absorption
is through the villi of the small intestine into the blood stream and 90
of the
iodine of the thyroid gland is in organic combination and stored in the
follicular colloids as thyroglobulin.
Inorganic
Iodine is mostly excreted by the kidney. Milk of lactating women also contains
some iodine.
A
deficiency of iodine leads to a decreased production of thyroxine, and in turn
a lowered rate of energy metabolism. In an attempt to produce more thyroid
hormones the thyroid gland enlarges. This condition is called simple or endemic
goiter.
Fluorine
exists in the body as compounds called fluorides.It is used as an
anti-coagulant during collection of blood for the determination of blood sugar.
· Fluorine is required in traces for the development
of bones and teeth.
· It is necessary for the prevention of dental
caries.
· It is used in combination with vitamin D for the
treatment of osteoporosis.
The body
receives fluorine mainly from drinking water, in which concentration varies
with soil content. Some sea fish and tea also contain small amounts of
fluorine.
Absorption
of fluoride is via the small intestine
into the blood stream. Most of the fluorides that are not retained by the bones
and teeth are excreted rapidly into the urine. It is also excreted through
sweat and intestine.
The
absence of fluorine in the diet causes dental caries.
Adult
human body contains approximately 1 to 2 grams of zinc. Like iron, zinc is
absorbed according to the body needs. Prostate gland is very rich in zinc.
·
Zinc forms an integral part of several metallo- enzymes in the body.
·
Zinc is essential for growth and reproduction.
·
It has role in maintaining the plasma concentration of vitamin A.
·
Zinc is essential for the storage of insulin in the β-islet cells.
·
Zinc is necessary for wound healing.
Fish,
meat, liver, egg and certain sea foods are high in zinc. Vegetable sources are
cereals, pulses, yeast and wheat germ. Milk including breast milk also is a
good source of zinc. The colostrum is an especially rich source.
Zinc
present in animal foods is well absorbed in the small intestine, especially
from the duodenum. Zinc present in plant foods are poorly absorbed due to the
presence of phytic acid which interferes with its absorption. Zinc is mostly
excreted in urine.
· Zinc deficiency causes poor growth and hypogonadism
during adolescence.
· In zinc deficiency, there is poor wound healing.
· Zinc deficiency may result in impairment of
sensitivity to taste.
· Deficiency
of zinc may interfere with storage and secretion of insulin.
· Zinc
deficiency causes alopecia (hair loss)
Cobalt
is a component of vitamin B12. Elemental cobalt of the diet can be converted to
Cobalamine by the intestinal bacteria. Cobalt occurs in small amount in all
tissues, higher concentrations occur in liver and kidneys.
Most of the cobalt is present in
vitamin B12, which is necessary for maturation of red blood cells.
Cobalt is an activator of the enzyme
Phosphoglucomutase and glycyl - glycine peptidase.
It is largely available in food.
Normal average diet contains about 5 to 8 micro grams of cobalt. One μg of
vitamin B12 contains ~0.0225- 0.045 μg of cobalt.
Cobalt is absorbed from the small
intestine. About 65% of ingested cobalt is excreted in the urine and the
remaining in the feces.
Cobalt deficiency is rare in human
beings.
Manganese is an essential trace
element. It is present as Mn2+ ion and found in high concentrations
in the mitochondria.
·
Manganese acts as a cofactor for number of enzymes including arginase,
hexokinase and isocitrate dehydrogenase.
·
Manganese is essential for normal bone structure, reproduction and
functioning of the central nervous system.
·
Manganese also functions with vitamin K in the formation of prothrombin.
·
It inhibits lipid peroxidation.
·
Manganese also participates in glycoprotein and
proteoglycan synthesis.
·
It helps in Porphyrin synthesis.
·
Manganese is involved in fatty acid and cholesterol synthesis.
Manganese
is universally distributed in plant and animal tissues, nuts, cereals and
vegetables. The average diet can provide approximately 3 to 4 mg of
manganese.Tea is exceptionally rich in manganese.
Manganese
is readily absorbed in the small intestine. Normally 3 to 4 % of Manganese in
diet is absorbed. Large quantity of Manganese is excreted mostly in the feces.
Only very small quantities of manganese are excreted in the urine.
Manganese
absorption is inhibited by iron.
A deficiency of Mn reduces appreciably the
synthesis of oligosaccharides.
The
deficiency of Manganese leads to impaired growth and skeletal abnormalities.
Chromium
is widely distributed throughout the body. The adult human body contains only 6
mg of chromium.
·
Chromium accelerates the utilization of glucose.
·
It reduces serum cholesterol level.
·
Chromium is also said to be important in the metabolism of plasma
lipoproteins.
Chromium
is highly available in average diets. Significant amount of chromium is obtained in the diet by
cooking foods in steel containers.
It is
absorbed in the small intestine.
Chromium
is mainly excreted in urine.
Chromium
deficiency is characterized by impaired growth, weight loss and disturbances in
glucose, lipid and protein metabolism.
Molybdenum
occurs in traces in the human body.Molybdenum occurs in some hemoflavo
proteins.
·
Molybdenum is required for the function of metallo-enzyme xanthine
oxidase.
·
Presence of small amount of molybdenum helps in the utilization of
copper.
Molybdenum
is available in normal diets. Liver and kidney are good animal sources. Whole
grains and legumes are vegetable sources.
About 50
- 70 % of the ingested Molybdenum is readily absorbed in the small intestine.
About half of the absorbed molybdenum is excreted in urine.
Molybdenum
deficiency is rare in human beings.
Selenium is an essential trace element for all species including humans.
·
Selenium is essential for normal growth and fertility.
·
Selenium is a component of the enzyme which reduces oxidized
glutathione.
·
It is involved in immune mechanism and synthesis of ATP.
·
Vitamin E and Selenium prevent peroxidative damage to cellular and
sub-cellular organelles and chiefly the membrane.
·
Selenium may be a cancer protective agent.
·
Supplements of selenium probably protect against toxic effects of heavy
metals like mercury and silver.
Selenium
is largely present in different foods. Selenium is present in foods of plant
origin grown in selenium rich soils. Any normal diet can meet the daily
requirement of selenium.
The principal dietary forms of selenium, selenocysteine and selenomethionine are absorbed from gastrointestinal tract. Selenium
homeostasis is achieved by removal of excess selenium in urine.
Selenium
deficiency is very rarely seen in human beings. Deficiency of selenium leads to
muscular dystrophy and heart diseases.
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