Food and nutrition.pdf

Function of Food 127of vitamin D, are described in Chapter 18. As vitamin. D is produced inhumans by the action of the sun on the skin, deficiency is not common intropical countries, although synthesis of vitamin D may possibly bereduced in darkly pigmented skin. Rickets and osteomalacia are seensporadically but are more common in areas where tradition or religionkeeps women and children indoors. Many cases have been reported fromYemen and Ethiopia. The conditions are manifested mainly by skeletalchanges.ToxicityLike other fat-soluble vitamins, vitamin D taken in excess in the dietis not well excreted. Consumption of large doses j which has mostcommonly resulted from overdosing of children with fish-liver oilpreparations, can lead to toxicity. Overdosing may lead to hypercalcaemia,diagnosed from high levels of calcium in the blood. Toxicity usually beginswith loss of appetite and weight, which may be followed by mentaldisorientation and finally by kidney failure. Fatalities have been recorded.Other VitaminsThe two fat-soluble vitamins (A and D) and the six water-solublevitamins (thiamine, riboflavin, niacin, vitamin B12 folates and vitamin C) .have been described in some detail because these are the vitamins mostlikely to be deficient and to be of public health importance in nonindustrializedcountries. Five other vitamins, although vital to humanhealth, are not very commonly deficient in human diets and so are of lesspublic health importance. These are vitamin B(51 biotin, pantothenic acid,vitamin E and vitamin KVitamin 8 6 (Pyridoxine)Vitamin B6 is a water-soluble vitamin widely present in foods of bothanimal and vegetable origin. It is important as a coenzyme in manymetabolic processes. Primary dietary deficiency is extremely rare, butvitamin B6 deficiency became common in tuberculosis patients treatedwith the drug isoniazid. The patients developed neurological signs andsome times also anaemia and dermatosis. Now it is common to provide10 mg of vitamin B6 by mouth daily to those receiving large doses ofisoniazid. Vitamin B6 is relatively expensive, however, and the routineadministration of vitamin B6 to patients receiving isoniazid increases thecost of treatment of tuberculosis.BiotinBiotin is another water-soluble vitamin of the B complex group. It is