The current RDA of 75 milligrams for women was set by the Food and Nutrition
Board of the National Academy of Sciences based on data that had been gathered
for men, says Dr. Mark Levine, chief of NIDDK’s Molecular and Clinical Nutrition
Section and lead author of the study. "With the new data, we can make a more
accurate recommendation for women."
Using Food and Nutrition Board criteria, Levine, NIDDK colleagues Dr. Yaohui
Wang and Dr. Sebastian Padayatty, and Dr. Jason Morrow of Vanderbilt studied
long-term vitamin C uptake in 15 women. The healthy women, aged 19 to 27, were
evaluated from 158 to 214 days at NIH. After they were put on a diet that depleted
them of vitamin C, the women received daily vitamin C doses that varied from 30 to
2,500 milligrams. The researchers found that at doses of 100 to 200 milligrams, cells
and blood plasma nearly reached their saturation points for vitamin C. The authors
believe their study is the first to describe the relationship between vitamin C doses
and steady-state concentrations in healthy young women.
Vitamin C clearly prevents deficiency diseases like scurvy, but what higher
concentrations might do is unclear. Levine says eating five fruits and vegetables daily
would give a healthy woman approximately 200 milligrams of vitamin C and provide
other health benefits such as decreased cancer risk.