最近由國家科學院發表的維他命C每天建議攝取量，建議男人每天攝取90 mg/d的維他命C。然而，因為婦女的資料有限，所以用男性的資料外推，約每天75 mg/d。一份在八月十四日The Proceedings of the National Academy of Sciences的新研究指出，這份每天建議攝取量太低了，婦女們也該每天攝取90 mg/d的維他命C。主筆者Mark Levine, MD,分子及臨床營養團隊領導人、國立糖尿病、消化及腎臟疾病研究協會的資深醫師告訴WebMD：「如果每天有五份的蔬果已能提供約兩百毫客的份量，就沒有必要為了達到這樣的攝取量而再服用另外的補充品。」
RDA for Vitamin C Raised for Women
Young, Healthy Women Need as Much C as Men
By Denise Mann
WebMD Medical News
Reviewed by Aman Shah, MD
Aug. 14, 2001 -- Recent recommended daily allowances (RDA) released by the National Academy of Sciences called for men to consume 90 mg/d of vitamin C. But because there were inadequate data for women, a 75 mg/d recommendation was made by extrapolating the men's data. A new study in the Aug. 14 issue of The Proceedings of the National Academy of Sciences shows that this number is too low and that the RDA for women ought to be 90 mg/d as well.
"There is no need to take supplements to achieve this level; five servings of fruits and vegetables actually provide about 200 milligrams," lead author Mark Levine, MD, chief of molecular and clinical nutrition and senior staff physician at the National Institute of Diabetes and Digestive and Kidney Disease in Bethesda, Md., tells WebMD.
Levine and colleagues conducted a depletion-repletion study in which 15 healthy women were hospitalized for about 6 months and initially fed a diet that contained <5 mg/d of vitamin C. When vitamin C levels were depleted -- without evidence of scurvy -- the level of vitamin C was gradually increased to 2,500 mg/d, and the levels of vitamin C and its metabolites were measured.
The dose-response curve was sigmoidal. The researchers note that at doses less than 100 mg/d, the dose-response was linear, suggesting that vitamin C intake levels up to this point were appropriate.
Calling the new report a "pretty careful study," Jane Higdon, RN, PhD, a research associate at the Linus Pauling Institute at Oregon State University in Corvallis, Ore., says it is "probably a good reason to raise the RDA. No one has ever done a study like this in women."
Older recommendations just extrapolated male data to a lower body weight, she says.
The Linus Pauling Institute, which is founded on the principles of Nobel Prize winner and staunch vitamin C-advocate Linus Pauling, currently recommends that all healthy men and women consume 200 mg of vitamin C per day. "There is good evidence to suggest that if you go over this, it won't increase plasma or tissue levels of vitamin C much more," Higdon tells WebMD.
"[You should] try to get it in fruits and vegetables. But we recognize that less than half of the population actually gets their five servings a day, so we don't see anything wrong with a supplement either," she says.
"Vitamin C has numerous benefits, and this is yet another example of how we are finding through gender-based medicine that what's good for the goose is not necessarily good for the gander," says Neshanic Station, N.J.-based women's health expert Donnica Moore, MD.
"Women are not just smaller versions of men," she says.