Vitamin C RDA should be doubled, says Linus Pauling Institute researcher

By Stephen Daniells

- Last updated on GMT

An excellent diet could provide 200 mg of vitamin C a day... But most people do not have an excellent diet...
An excellent diet could provide 200 mg of vitamin C a day... But most people do not have an excellent diet...

Related tags Vitamin c

The recommended dietary allowance (RDA) for vitamin C should be increased to 200 milligrams per day for adults, an increase of over 100% from current levels in the United States, says a new analysis from the Linus Pauling Institute at Oregon State University.

According to a new article in Critical Reviews in Food Science and Nutrition​, levels should be raised from the current levels of 75 mgs per day for women and 90 mg per day for men to an optimum level that ensures cell and tissue saturation, that poses no risk, and that may have significant effects on public health at almost no expense – about a penny a day if taken as a dietary supplement.

Current levels are dictated by the levels required to prevent the vitamin C deficiency disease of scurvy.

Look beyond ‘flawed’ clinical trials

"It's 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 Professor Balz Frei, director of the Linus Pauling Institute.

"Significant numbers of people in the U.S. and around the world are deficient in vitamin C, and there's growing evidence that more of this vitamin could help prevent chronic disease.

"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."


Duffy MacKay, vice president, scientific and regulatory affairs, for the Council for Responsible Nutrition (CRN), told NutraIngredients-USA: “We’re in agreement with Dr. Frei in this area and applaud the authors for embracing the need for a new paradigm in micronutrient research.

“CRN, along with academic scientists, has for several years now been leading the way in encouraging the scientific community, the regulatory world, and the media to understand when it comes to studying nutrition, we need to move beyond the traditional evidence-based drug model of RCTs as the only gold standard.” 

Totality of evidence

Prof Frei and his co-workers note that nutrient recommendations are based on short-term trials that are ill suited to demonstrate the disease prevention capabilities of substances that are already present in the human body and required for normal metabolism. Micronutrient benefits for reducing the risk of many chronic diseases may not reveal themselves until many years or even decades, they said.

"We believe solid research shows the RDA should be increased,"​ said Frei. "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."

Marginal deficiency

Even at the current low RDAs, various studies in the U.S. and Canada have found that about a quarter to a third of people are marginally deficient in vitamin C, and up to 20% in some populations are severely deficient, wrote Frie and his co-workers.

-          A recent analysis of 29 human studies concluded that daily supplements of 500 milligrams of vitamin C significantly reduced blood pressure, both systolic and diastolic. High blood pressure is a major risk factor for heart disease and stroke, and directly attributes to an estimated 400,000 deaths annually in the US.

-          A study in Europe of almost 20,000 men and women found that mortality from cardiovascular disease was 60% lower when comparing the blood plasma concentration of vitamin C in the highest 20% of people to the lowest 20%.

-          Another research effort found that men with the lowest serum vitamin C levels had a 62% higher risk of cancer-related death after a 12-16 year period, compared to those with the highest vitamin C levels.

Source: Critical Reviews in Food Science and Nutrition
Volume 52, Issue 9, doi:10.1080/10408398.2011.649149
“Authors' Perspective: What is the Optimum Intake of Vitamin C in Humans?”
Authors: B. Frei, I. Birlouez-Aragon, J. Lykkesfeldt

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