TRACE ELEMENTS & HEALTH
Trace elements are components of our diet which are required in minute quantities but are essential for normal growth and health. the main nutrients required by us are proteins, carbohydrates and fats and they make up the macronutrients. the other substances that are required in very small quantities are called micronutrients. of the about 30 different micronutrients required by us about half are the various vitamins. some elements like sodium, potassium, phosphorus, calcium and magnesium are required in slightly larger quantities while others are required in truly miniscule amounts. these latter are known as the trace elements. notwithstanding the fact that their requirement is really small, a deiciency of any of them has the potential to cause signiicant clinical problems. presence of excessive quantities of trace elements in our body may also lead to major health problems. the elements which are generally considered as trace elements from the nutritional point of view are iodine, manganese, zinc, iron, chromium, selenium, molybdenum, luorine, copper and cobalt. the commonest trace element deiciencies encountered clinically are those of iron and iodine.
iron is critical for oxygen transport and delivery. red blood cells contain haemoglobin of which iron is an integral component. haemoglobin combines with oxygen when oxygen saturation is high as occurs in our lungs. in tissues the oxygen saturation is low and haemoglobin readily gives up oxygen for use by cells in metabolic processes including generation of energy. without oxygen tissues cannot survive for long and some organs such as the brain cannot withstand deprivation of oxygen even for short periods. anaemia is the term used for a low haemoglobin level in blood. There are many causes of anaemia But Iron DEiCIEnCy Is the commonest cause all over the world. It contributes to substantial ill health and poor quality of life in a surprisingly large percentage of the global population. Iron is also a key component of myoglobin which is a protein present in heart and other muscles. Myoglobin serves as a store for oxygen for utilization during strenuous activities and also facilitates delivery of oxygen to muscle. The importance of myoglobin in providing a ready store of oxygen can be appreciated from the fact that racehorses have unusually high levels of myoglobin in their muscles.
Although iron is essential for normal health, the requirement is very small. The recommended daily allowance (RDA) for an adult male is 8 mg. For adult females the RDA is 18 mg as long as the menstrual cycle is still active and thereafter it is 8 mg. The RDA during pregnancy is substantially higher at 27 mg. Iron is available from nutritional sources in two forms. Heme iron is available from lean meat and seafood. Nonheme iron sources include vegetables, nuts and beans. in some countries such as usa and canada lour and cereals are fortiied with iron and such products also become important sources of iron. in general, heme iron is better absorbed than nonheme iron. heme iron also helps absorption of non-heme iron. this is important because non-heme iron is more abundant in most people’s diet. breast milk contains iron suficient for the infant’s needs only till the age of about 4 to 6 months. infant formulas are fortiied with iron. the problem with iron, as with many other metallic elements, is that we cannot eliminate excess stores easily. iron in excess of needs is harmful to us and to avoid accumulation our body controls the absorption of iron in an elaborate way. also, many factors inluence the absorption such as whether it is heme iron or non-heme iron. iron absorption is also affected by whether it is in the divalent ferrous or the trivalent ferric form. the presence of other substances in food may enhance or retard absorption of iron. for example, vitamin c in food increases iron absorption while phytates present in some plant derived foods decrease absorption of iron.
iron deiciency is much commoner in women. they lose a little iron regularly from the blood low during the menstrual cycle. also, they have a higher requirement of iron during pregnancy. blood loss due to any cause may lead to iron deiciency and anaemia. common causes include heavy menstrual bleeding, use of aspirin and other nsaid pain killers which often cause bleeding from the gastrointestinal tract and diseases of the gastrointestinal tract such as gastritis, ulcer and oesophagitis. in endemic areas hookworm infestation is a very common problem. walking barefoot, usually in some agricultural communities with practice of defaecation in the open, allows hookworm larvae to penetrate intact skin of the foot and migrate to the duodenum in the small intestine. here they attach to the wall and suck blood. heavy infestation is not at all uncommon and causes severe anaemia. the other major contributor to iron deiciency is poor nutrition.
iron deiciency is relatively easy to correct provided the underlying cause is attended to and further blood loss is prevented. oral iron is notorious for the complaints of intolerance but most patients can tolerate lower doses. special preparations which cause less gastrointestinal discomfort but are much costlier may also be better tolerated. iron doses need to be taken after food and may impart a dark colour to stools. an alternative is injectable iron, preferably as intravenous injection. the entire deicit can be made up by a single injection in most cases. there is a small but deinite risk of severe reaction during intravenous iron administration. when planning this injection adequate monitoring and availability of resuscitative measures is a must.
accumulation of iron in our bodies is also harmful. it causes what is called haemochromatosis with main complications being cirrhosis of liver and heart failure. haemochromatosis is a genetic disease causing an inappropriately high absorption of iron from the intestine. women are protected to some degree by the safety valve of iron loss in menstrual low. secondary haemochromatosis may also occur in people taking too much iron. patients with severe anaemia such as thalassaemia require regular transfusion. each transfusion represents an iron load which cannot be eliminated without special medication. taking too much oral iron, usually as misguided medication for anaemia not due to iron deiciency may also cause secondary haemochromatosis.
iodine is another important trace element, being a component of thyroid hormones. thyroid hormones regulate the body’s metabolic processes. our requirements of iodine are miniscule. the rda for adult men and women for iodine is only 150 micrograms (0.15 mg). women who are pregnant or are breastfeeding are recommended to take 220 and 290 microgram iodine respectively. however, natural sources of iodine are limited to seafood and sea salt. people living in hilly inland areas and using salt derived from rock rather than from sea water used to be at substantial risk for iodine deiciency. most health authorities have implemented the simple expedient of adding a small quantity of iodine to salt available in the market to prevent iodine deiciency. iodized salt usually contains about 400 microgram iodine in a teaspoon. the thyroid takes up iodine avidly. should iodine be deicient the thyroid enlarges in an attempt to achieve its goal of producing adequate quantities of thyroid hormones. enlargement of the thyroid is called a goitre
and with severe iodine deiciency a goitre can attain an enormous size. more importantly, the lack of thyroid hormones results in clinical hypothyroidism. a deiciency of thyroid hormones during foetal stage or in early childhood is really disastrous as it results in the condition called cretinism. the cretin suffers permanent mental and physical retardation which cannot be corrected by iodine supplementation or administration of thyroid hormones later in life. the effects of deiciency of thyroid hormones cause signiicant clinical problems in adults too. fortunately, widespread iodisation of salt has reduced the occurrence of iodine deiciency and resultant thyroid deiciency disorders to a great extent. many people, however, do opt for noniodised salt and may be at risk for iodine deiciency. taking too much iodine is also hazardous. this too may be associated with development of a goitre and disturbances in production of thyroid hormones. there is also a risk of development of thyroid papillary cancer when taking in too much iodine on a long-term basis.
while deiciency of iron and of iodine are the commonest trace element disorders the other trace elements also serve critical functions and may cause clinical disease, although less commonly. in general, unless one lives in an
area of endemic deiciency, these trace element disorders can be avoided by eating a normal balanced diet. supplementation is usually not required unless one’s diet is unsatisfactory.
Iron is critical for oxygen transport and delivery. Red blood cells contain haemoglobin of which iron is an integral component. Haemoglobin combines with oxygen when oxygen saturation is high as occurs in our lungs