Evolution and the need for ascorbic acid.

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(-1).