Recommended dietary intakes (RDI) of vitamin C in humans.

Vitamin C is unevenly distributed throughout all body cells and fluids. A total-body pool of 900 mg (5.11 mmol) in an adult male meets the following criteria of a satisfactory vitamin C status: it is threefold higher than one that prevents scurvy, no known health advantages accrue at higher pool sizes, absorption efficiency is high and urinary loss low at appropriate intakes, and a 1-mo reserve allows for periods of low intake or stress. To maintain a suitable body pool in healthy 76-kg men and 62-kg women requires daily intakes (RDI) of 40 mg (227 mumol) and 30 mg (170 mumol), respectively. Reasons for not increasing RDI values to enhance iron absorption and to prevent nitrosamine formation are given. The specific association of normal intakes of dietary vitamin C with cancer is very weak and not quantifiable. Advisable intakes for children, pregnant and lactating women, and the elderly are considered. The present recommendations are in better accord with current information than are the 1980 RDA values.