The assessment of vitamin C nutrition in man

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Abstract
Demonstration of saturation is defined as excretion of 1/3 of a test dose of 700 mg./140 lb. in the subsequent 24 hrs.; a "state of saturation" is attained when this dose is deducted from the total dose required to demonstrate saturation or when the plasma conc. reaches 0.8 mg./100 ml. The curve "initial plasma conc. against total dose required to produce a state of satn." is hyperbolic, the maximum rate of change of dose occurring at a plasma conc. of approx. 0.4 mg./lOO cc. This conc. is equivalent to demonstration of saturation in 2 days. Plasma conc. detns. with subjects on known ascorbic acid intakes showed that if the initial conc. is higher than the final, a period of at least 30 days is required for the latter to reflect the new intake. The time required for this when ascending from a lower to a higher intake is much less. It is concluded that at least 60 mg. of ascorbic acid is required daily to maintain a plasma conc. of 0.4 mg./lOO ml. and this conc. indicates a satisfactory state of vit. C nutrition provided the subject has not received, within the previous 30 days, an appreciably higher intake of ascorbic acid than at the time of the test.