Food and nutrition.pdf

128 Function of Foodfound widely in food, and deficiency in humans is extremely rare. Thevitamin is very important, however, in physiological and biochemicalmetabolic processes. Avidin in uncooked egg white prevents absorptionof biotin in animals and humans. Rats fed egg white as their only sourceof protein become thin and wasted and develop neuropathies anddermatitis. Biotin deficiency has been reported in a very few cases, inpeople consuming mainly egg white and in a few intravenously-fedpatients with some special forms of malabsorption.Pantothenic AcidPantothenic acid, a water-soluble vitamin, is present in adequateamounts in almost all human diets. It has important biochemical functionsin various enzyme reactions, but deficiency in humans is very rare. Aneurological condition described as burning feet syndrome, reported inprisoners of war held by the Japanese between 1942 and 1945, was ascribedto a deficiency of this vitamin.Vitamin E (Tocopherol)Vitamin E, a fat-soluble vitamin, is obtained by humans mainly fromvegetable oils and whole-grain cereals. It has been termed the" anti-sterilityvitamin" or even the" sex vitamin" because rats fed on tocopherol-deficientdiets cannot reproduce: males develop abnormalities in the testicles andfemales abort spontaneously.Because of its relationship to fertility and to many conditions inanimals, vitamin E is widely self-prescribed and is not uncommonlyrecommended by physicians for a variety of human ills. However, truedeficiency is probably rare; it occurs mainly in association with severemalabsorption states (when fat is poorly absorbed), in genetic anaemias[including glucose-6-phosphatase dehydrogenase (G-6PD) deficiency] andoccasionally in very low-weight babies.Vitamin E (like vitamin C) is an antioxidant, and because of its abilityto limit oxidation and to deal with damaging free radicals it is sometimesrecommended as a possible preventive for both arteriosclerosis and cancer.Its presence in oils helps prevent the oxidation of unsaturated fatty acids.Vitamin KVitamin K has been termed the "coagulation vitamin" because of itsrelationship to prothrombin and blood coagulation, and because it issuccessfully used to treat a bleeding condition of newborn infants(haemorrhagic disease of the newborn). Humans obtain some vitamin Kfrom food, and some is also made by bacteria in the intestines. Newborninfants have a gut free of organisms, so they do not get vitamin K from