Chronically increased vitamin intake and vitamin status of healthy men.

The effects of an 8-wk chronically increased vitamin intake on the biochemical parameters of vitamin status in 498 healthy men were estimated. A control group of 520 volunteers, given a placebo instead of vitamins, was also examined to control the changes that occur in biochemical vitamin supply parameters. Comparison of the measurements between the groups showed that plasma concentrations of folate, vitamin B12, and tocopherol; the urine concentrations of thiamine and riboflavin; and the activities of measured vitamin-related enzymes increased linearly and independently to the baseline vitamin status by the absolute value. Plasma concentrations of ascorbic acid, activity coefficients, and urinary excretion of 4-pyridoxic acid increased more in men with lower baseline values. The plasma retinol concentration did not change despite doubling the vitamin A intake.