OREGON STATE UNIVERSITY

How much vitamin C is enough?

06/02/1998

CORVALLIS, Ore. - Science is taking another hard look at whether or not the recommended amount of vitamin C needed to prevent scurvy - in other words, enough to keep your teeth from falling out - is also the optimal amount for health and the prevention of other diseases.

The process still has a way to go, but it's quite possible the time-honored 60 milligrams per day that has been the "recommended daily allowance" for years will be edged up as researchers continue to explore the value of this vitamin in everything from heart disease to diabetes and cancer.

Researchers in the Linus Pauling Institute at Oregon State University are preparing an analysis of many studies done over the years on the proven, demonstrable benefits of various levels of vitamin C intake, and will soon be submitting a report to the Food and Nutrition Board of the National Academy of Sciences, which is considering changes in the RDA for vitamin C and other antioxidants.

"We aren't sure yet about our final recommendation, but based upon a preliminary review of many studies done over the past 15 years, a number that seems to stand out right now is about 100 milligrams per day," said Anitra Carr, a research associate with the Linus Pauling Institute.

"At least in healthy young adult males, a total vitamin C intake either from food or supplements of around 100 milligrams a day is enough to reach tissue saturation levels of this nutrient," Carr said. "And those are the levels that the best scientific studies are clearly associating with optimal health and the ability of this vitamin to help in disease prevention."

Many people take far higher doses of the vitamin than that, Carr said, and there's no credible evidence it's harming them. But proven benefits above 100 milligrams also appear less obvious, although continued research may determine that people with certain illnesses or less-than-perfect health habits could benefit from higher levels.

And dietary habits are a continued problem, Carr said, with studies indicating that many, if not most Americans - especially those in the hot dog and pizza generation - might benefit from modest vitamin supplementation.

"Current guidelines suggest five to nine servings a day of fresh fruits and vegetables, which will provide about 220 milligrams of vitamin C," Carr said. "Anyone who does that should be fine. But one study of U.S. children and teens found only about one-third of them actually followed the guidelines."