RDA of Vitamin C should Be Higher

CORVALLIS, Ore.The recommended dietary allowance (RDA) of vitamin C is less than half of what it should be, according to a recent report, because medical experts insist on evaluating this natural nutrient in the same way they evaluate pharmaceutical drugs.

Researchers in Critical Reviews in Food Science and Nutrition, said there is compelling evidence that the RDA of vitamin C should be raised to 200 mg/d for adults, up from its current levels in the United States of 75 mg for women and 90 for men (Crit Rev Food Sci Nutr. 2012 Sep;52(9):815-29). 

Rather than just prevent vitamin C deficiency disease of scurvy, researchers say its appropriate to seek optimum levels that will saturate cells and tissues, pose no risk and may have significant effects on public health at almost no expense.

Its time to bring some common sense to this issue, look at the totality of the scientific evidence, and go beyond some clinical trials that are inherently flawed," said Balz Frei, professor and director of the Linus Pauling Institute at Oregon State University (OSU).

Significant numbers of people in the United States and around the world are deficient in vitamin C, and theres growing evidence that more of this vitamin could help prevent chronic disease," Frei said. The way clinical researchers study micronutrients right now, with the same type of so-called phase three randomized placebo-controlled trials used to test pharmaceutical drugs, almost ensures they will find no beneficial effect. We need to get past that." 

Unlike testing the safety or function of a prescription drug, researchers said, such trials are ill suited to demonstrate the disease prevention capabilities of substances that are already present in the human body and required for normal metabolism. Some benefits of micronutrients in lowering chronic disease risk also show up only after many years or even decades of optimal consumption of vitamin C, a factor often not captured in shorter-term clinical studies. 

A wider body of metabolic, pharmacokinetic, laboratory and demographic studies suggests that higher levels of vitamin C could help reduce the chronic diseases that today kill most people in the developed world such as heart disease, stroke, cancer, and the underlying issues that lead to them, including high blood pressure, chronic inflammation, poor immune response and atherosclerosis. 

We believe solid research shows the RDA should be increased," Frei said. And the benefit-to-risk ratio is very high. A 200 milligram intake of vitamin C on a daily basis poses absolutely no risk, but there is strong evidence it would provide multiple, substantial health benefits." 

An excellent diet with the recommended five to nine daily servings of fruits and raw or steam-cooked vegetables, together with a six-ounce glass of orange juice, could provide 200 milligrams of vitamin C a day. But most are not getting this diet. Even at the current low RDAs, various studies in the United States and Canada have found that about one-quarter to one-third of people are marginally deficient in vitamin C, and up to 20 percent in some populations are severely deficient.

Even marginal deficiency can lead to malaise, fatigue and lethargy, researchers note. Healthier levels of vitamin C can enhance immune function, reduce inflammatory conditions, such as atherosclerosis and significantly lower blood pressure. 

Critics have suggested that some of these differences are simply due to better overall diet, not vitamin C levels, but the scientists noted in this report that some health benefits correlate even more strongly to vitamin C plasma levels than fruit and vegetable consumption. 

Scientists in France and Denmark collaborated on this report. Research at OSU on these issues has been supported by the National Center for Complementary and Alternative Medicine (NCCAM), a division of the National Institutes of Health (NIH).