Ascorbic acid in cholesterol metabolism and in detoxification of xenobiotic substances: problem of optimum vitamin C intake.

There are extreme contradictions in the question of an optimum intake of vitamin C. The Recommended Dietary Allowances (RDA) in the USA, Great Britain, and many other countries range from 30 to 60mg for an adult man or woman, whereas the proponents of megadoses recommend as much as 18,000mg per day. Critical opinions against both the official RDA and the hypothesis of megadoses are summarized. Ideal RDA should be based on studies with increasing vitamin C doses in which the efficiency of the ascorbate-dependent systems would be correlated with the vitamin C concentration in the target tissues. On the basis of correlations of the hepatic vitamin C levels in guinea pigs with the rate of cholesterol degradation and the activity of microsomal detoxification systems, it is suggested that such intake of ascorbic acid is optimum that ensures a maximum body pool and maximum steady-state levels of vitamin C in the tissues. It is probable that in healthy adults, such a dose ranges from 100 to 200mg and that in stress conditions, it exceeds 200mg per day.