TAILIEUCHUNG - Ebook ABC of nutrition (4/E): Part 2
(BQ) Part 2 book “ABC of nutrition” has contents: Vitamins and some minerals, overweight and obesity, measuring nutrition, therapeutic diets, food poisoning, food sensitivity, processing food, nutritional support, some principles. | 10 Vitamins and some minerals No animal can live on a mixture of pure protein, fat and carbohydrate, and even when the necessary inorganic material is carefully supplied the animal still cannot flourish. The animal body is adjusted to live upon plant tissues or the tissues of other animals and these contain countless substances other than the proteins, carbohydrates and fats. Sir Frederick Gowland Hopkins (1906) Deficiencies of vitamins still occur in affluent countries: folate, thiamin, and vitamins D and C. Some of these deficiencies are induced by diseases or drugs. In developing countries deficiency diseases are more prevalent. Vitamin A deficiency (xerophthalmia), for example, is a major cause of blindness. Some vitamins may have useful actions above the dose that prevents classic deficiency disease—for example, vitamins A, C, and B-6; nicotinic acid has been used to treat hyperlipidaemia. Vitamins have caught the popular imagination, and they are also big business. Many people take over the counter vitamins without medical advice and a few unorthodox practitioners prescribe “megavitamin therapy”. Doctors therefore need to know the symptoms of overdosage. Definition Vitamins are: (a) Organic substances or groups of related substances (b) found in some foods (c) substances with specific biochemical functions in the human body (d ) not made in the body (or not in sufficient quantity) (e) required in very small amounts. Many people seem to have lost sight of point (e), but it appears in all dictionary definitions and can be seen in the table of requirements. The daily requirement of most vitamins is around 1 mg, the weight of one grain of raw sugar. There are no exceptions to points (a), (b), and (e). On point (c), the biochemical action of most vitamins can now be visualised, but those of vitamins A and C are not yet explained fully, and the active metabolite of vitamin D acts as a hormone. Exceptions to point (d) are that certain carotenoids can replace .
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