Ascorbic acid vitamin species differences

Mobilization and Metabolism. The total ascorbic acid body pool in healthy adults has been estimated to be approximately 1.5 g, which increases to 2.3—2.8 g with intakes of 200 mg/d (151—158). Depletion of the body pool to 600 mg initiates physiological changes, and signs of clinical scurvy are reported when the body pool falls below 300 mg (149). Approximately 3—4% of the body pool turns over daily, representing 40—60 mg/d of metabolized, or consumed, vitamin C. Smokers have a higher metaboHc turnover rate of vitamin C (approximately 100 mg/d) and a lower body pool than nonsmokers, unless compensated through increased daily intakes of vitamin C (159). The metaboHsm of ascorbic acid varies among different species. 

This method is dependent on the species. The vitamin requirements differ among the common laboratory animals. The classic example is ascorbic acid, which is not a vitamin in most animals. Humans do not exhibit specific defi-... 

Many remarkable species differences have been found among the coenzymes. Most plants and animals synthesize their own ascorbic acid which is (among other tasks) essential for the hydroxylation of proline and lysine in the biosynthesis of collagen. However, Man, other primates, and the guinea pig are notable exceptions, so that for them, and for them alone, it is a vitamin, and must be taken in with food. 

Abstract. Ascorbic acid differs from other vitamins in that an exogenous source is required by only a few animal species. It is pointed out that this fact indicates that the amount contained in a diet of raw natural plant food is less than the optimum intake, corresponding to the best health. This argument leads to the conclusion that the optimum daily intake is about 2.3 g or more, for an adult with energy requirement 2500 kcal day h... 

Ascorbic acid differs from the other vitamins in that it is required in the diet by only a few species of animals—man, other primates, the guinea pig, an Indian fruit-eating bat, and the red-vented bulbul and some related species of Pas-seriform birds. Other species of animals synthesize ascorbic acid. All mammals and other larger animals require vitamin A, thiamine, riboflavin, nicotinic acid, and pyridoxine as essential nutrients, although microoi anisms usually have the power to synthesize all or most of these substances. 

Ascorbic acid differs from the other vitamins in that most animal species continue to synthesize it despite its availability in natural foods. I think that the only reasonable explanation of this fact is that the foods available to most animals over the past several hundred million years have not provided a supply of ascorbic acid sufficient to justify the abandonment of the mechanism of its synthesis. We are accordingly able to make an estimate of the optimum daily intake of ascorbic acid, on the basis of this fact and the assumption that the foods listed in Table 1 represent approximately the foods available to the ancestors of existing animal species. 

C is rapidly excreted. About 4% of this pool is lost daily (fractional catabolic rate) after intermission of vitamin C supply. The biological half-time of the pool is therefore approximately 8-40 days (Homig, 1981). The first symptoms of scurvy occur upon reaching a total body pool of 300-400 mg. Table II shows data on the turnover rate of ascorbic acid for man and different species. Table III shows the ascorbic acid concentrations in organs and body fluids of the adult man. 

Furthermore, different organisms need different vitamins. More than 4000 species of mammals can synthesize ascorbic acid in their bodies, for instance, but humans are not among them. Ascorbic acid is therefore a human vitamin—what we all know as vitamin C—and must be obtained in our diet. Small amounts of more than a dozen other substances are similarly required by humans retinol (vitamin A), thiamine (vitamin Bi), and tocopherol (vitamin E), for instance. 

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