MICRONUTRIENTS & HEALTH
Werequireavariety of nutrient substances to meet energy requirements and to keep our bodies healthy. Some of these substances are required in relatively large quantities and they are conventionally termed macronutrients. These are the proteins, carbohydrates and fats which make up the bulk of our nutritional requirements. Other substances are required in minute quantities and are termed micronutrients. Even though the requirement of these micronutrients is very small, their need is critical and deiciency results in signiicant clinical problems. There are about 30 such nutrients which are required in trace amounts and so qualify to be termed as micronutrients. Examples of micronutrients include the various vitamins and trace elements such as calcium, iron, zinc, copper, etc.
Vitamins are organic compounds obtainable from diet which are essential for health and normal functioning of the body and which cannot be synthesised by the body. Vitamins are designated by a capital letter with a number also being used to identify some of them. The main vitamins are vitamin A, those of the B group, C, D, E and K. Vitamins are conventionally divided into two classes – water soluble and fat soluble vitamins. Vitamins A, D, E and K are fat soluble while vitamins of the B group and vitamin C are water
Vitamins are organic compounds obtainable from diet which are essential for health and normal functioning of the body and which cannot be synthesised by the body. Vitamins are designated by a capital letter with a number also being used to identify some of them
soluble. As a general rule, water soluble vitamins do not accumulate in our body even when we take large doses. Excess amounts are eliminated fairly easily, thus preventing build up. Fat soluble vitamins on the other hand cannot be easily eliminated and when taken in excess, they can accumulate and cause toxicity. Such a state of affairs almost never arises due to excessive dietary intake but does occur from oral or injectable administration of large doses of vitamin preparations.
The individual vitamins have varied functions which are by and large unrelated to each other. Provided one eats a normal reasonably balanced diet occurrence of vitamin deiciency for most of the vitamins is rare. However, when diet is not nutritious as may occur in famine conditions or as a result of social or medical problems including alcoholism or drug addiction vitamin deiciency does develop. People excessively picky in their selection of foods or those following speciic diets for religious purposes or as a matter of choice too are vulnerable to develop such deiciencies. One of the classical examples is the occurrence of scurvy in sailors in olden times. This is a vitamin C deiciency disease. During long sea voyages sailors had no access to fresh fruit or vegetables, the main sources of vitamin C. This resulted in scurvy which is associated with weakness and marked fatigue, bleeding from gums, swelling of feet
and anaemia and inally death if left untreated for long. The preventive and curative effects of lemons and other citrus fruits was discovered more than two centuries back. Over time, scurvy has become an extremely rare disease being seen only in exceptional circumstances of severe malnutrition. Deiciency of vitamin A is still a signiicant problem in some developing countries and this can lead to blindness. Administering vitamin A supplements to children in affected communities has been found to be very effective in combating such deiciency and preventing blindness.
In people eating a normal diet the only vitamin deiciencies that occur with any signiicant frequency are of vitamin D and vitamin
B12. Regarding vitamin D it can be contested that it should not be called a vitamin at all since it is possible for it to be produced in our skin by the action of sunlight. In spite of this possibility to make the vitamin ourselves and also in spite of fortiication of foods such as dairy products with vitamin D, deiciency continues to be very common. It is true that most of us living in the UAE avoid direct exposure to the sun for common sense reasons. Deiciency of vitamin D causes mild and relatively nonspeciic symptoms such as bone pains and fatigue in most affected individuals. Vitamin D deiciency is also believed to increase the risk for cardiovascular disease and some types of cancer. Severe vitamin D deiciency that causes the childhood
syndrome of rickets and the adult syndrome of osteomalacia is seen with any degree of frequency only in areas of the world aflicted by severe malnutrition. Vitamin D deiciency is treated with supplements of vitamin D. Supplements are available in small doses for prevention and much higher doses for treating established deiciency. Since vitamin
D can accumulate in the body when excessive doses are administered, caution needs to be exercised when taking high doses. Also, the really high dose (50,000 IU) oral preparations are recommended for once a week usage and this frequency should not be exceeded.
Vitamin B12 is the other vitamin deiciency which is relatively common. This vitamin can be sourced only from animal derived foods. People who follow a vegetarian or vegan diet are thus rendered vulnerable to this deiciency. Other individuals may also develop vitamin B12 deiciency but it is generally less common and less severe. Vitamin B12 deiciency also occurs due to inadequate production of a special protein called intrinsic factor by certain cells lining the stomach. Absorption of vitamin B12 takes place in the small intestine but depends on the presence of intrinsic factor. The classical form is called pernicious anaemia and occurs as an inherited disease in which one’s own antibodies act against stomach cells producing intrinsic factor. Surgery
on the stomach which removes this part of the stomach causes a similar deiciency of intrinsic factor leading to vitamin B12 deiciency. Diseases of the small intestine or surgery too may cause vitamin
B12 deiciency as this is the site of absorption of the vitamin. Deiciency of vitamin B12 causes anaemia and it causes neurological problems. Symptoms of the former include fatigue, weakness, breathlessness, palpitations, dizziness, etc. In later stages cardiac failure occurs. Neurological symptoms of vitamin B12 deiciency include tingling and numbness in the lower limbs progressing to weakness and unsteady gait. In older individuals it can cause symptoms such as memory loss and deterioration of other intellectual functions which may be misdiagnosed as Alzheimer’s disease. Severe vitamin B12 deiciency is a serious and potentially fatal disease. The recommended daily allowance (RDA) for Vitamin B12 is 2.4 mcg. This amount is readily available from diet in people eating a nonvegetarian diet. Most multi-vitamin pills used as general health supplements contain amounts adequate to prevent deiciency symptoms from developing even in strict vegetarians. Since intrinsic factor is required for vitamin B12 absorption, people lacking this substance cannot absorb vitamin B12 and hence oral doses are not recommended. However, high dose vitamin B12 (1000 mcg) oral preparations are available and at this concentration some absorption does occur even without intrinsic factor. However, since the absorption in such cases is fairly erratic and unreliable, a monthly injection of vitamin B12 is a better idea. Injection doses are generally of 1000 mcg which is more than adequate to cover the monthly requirement. Since unrequired vitamin is easily eliminated from the body, toxicity from accumulation is not a fear.
That deiciency of vitamins has the potential to cause serious illness is undoubted. However, vitamins have almost no beneits except to prevent deiciency related diseases. They are not magic substances that prevent or avert diseases unrelated to deiciency. They also do not have any invigorating properties providing strength and energy or make people feel or look younger. Vitamin preparations are meant only to prevent or treat deiciency states. Using them to derive any other type of beneit is at best hopeful thinking and at worst a health hazard. Most people eating a balanced and healthy diet do not need vitamin supplements. Although there is no real harm in taking a standard dose multi-vitamin pill daily, one should not expect any meaningful beneit beyond a placebo effect. However, taking high dose vitamin pills or injections is potentially harmful and this applies specially to preparations of vitamins D and A.
The other group of substances that are considered as micronutrients are the trace elements. These too are required in minute quantities to serve diverse and critical functions in our body. Deiciency or excess of these substances leads to major clinical problems. Some of the diseases are inherited while others are acquired due to diverse causes such as nutritional and environmental problems. The importance and impact of some of these trace elements on our health is considered next week.