Ascorbic acid intake and plasma levels in healthy elderly people.

Plasma ascorbic acid concentrations were determined in eight men and nine women over age 65 on controlled intakes of vitamin C. Plasma ascorbic acid levels were significantly lower in elderly men compared with women for vitamin C intakes ranging from 30 to 280 mg/d. A maximum steady-state level of 1.0 mg/dL (56.78 mumol/L) ascorbic acid was observed in male subjects at an intake of approximately 150 mg/d; female subjects approached a plasma ascorbate level of 1.0 mg/dL (56.78 mumol/L) with an intake of approximately 80 mg/d. At a total vitamin C intake of 60 mg/d, plasma ascorbate levels in men were estimated to be 0.4 mg/dL (22.71 mumol/L) or less. The amount of dehydroascorbic acid in plasma did not vary with intake of vitamin C.