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Higher RDA for Vitamin C Needed, How Much and Why

You need more vitamin C

Vitamin C is arguably the most recognized and popular vitamin, but some researchers say we aren't getting enough of it, which could be jeopardizing our health. A new report states that the RDA (recommended dietary allowance) of vitamin C needs to be higher, more than double the current levels, and here's why.

Vitamin C can help prevent chronic disease

Vitamin C is found in abundance in many foods, especially fruits and vegetables, and therein lies a major problem with this critical nutrient. According to the authors of the new study, led by vitamin C expert Balz Frei, professor and director of the Linus Pauling Institute at Oregon State University, most people do not eat the recommended amount of fruits and vegetables, which is five to nine servings per day.

The result, according to Frei, is that "Significant numbers of people in the US and around the world are deficient in vitamin C, and there's growing evidence that more of this vitamin could help prevent chronic disease." One way to attack this problem, say the authors, is to raise the RDA for vitamin C from the current 75 milligrams for women and 90 mg for men to 200 mg per day for adults.

The current RDA for vitamin C is the level needed to prevent scurvy, a vitamin C deficiency disease characterized by anemia, weakness, gum disease, and skin hemorrhaging. Although scurvy is rare in the United States, that does not mean people are getting the amount of vitamin C they need to ward off serious disease, say the authors.

In fact, the authors explained that up to one-third of people in the United States and Canada are marginally deficient in vitamin C. They also warned that up to 20 percent in some populations, including college students, are severely deficient.

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Frei and his colleagues believe there is a solid body of evidence indicating that higher intake of vitamin C could reduce the incidence of the significant killers in the world today: cancer, heart disease, stroke, and the underlying factors that contribute to them, such as atherosclerosis, chronic inflammation, high blood pressure, and a compromised immune system.

Studies of vitamin C
Here are just a few of the results from recent studies of vitamin C.

  • A new study from the University of Iowa reports that the properties of vitamin C "bring a rationale to its use to treat disease...as an adjuvant in the treatment of cancer."
  • A recent Johns Hopkins conducted meta-analysis of 29 human studies found that 500 mg per day of vitamin C significantly lowered both systolic and diastolic blood pressure.
  • A study published in the American Heart Journal in 2011 reported on nearly 20,000 men and women, noting that death from cardiovascular disease was significantly lower in those with the highest concentration of vitamin C.
  • A recent report in the Journal of Alzheimer's Disease noted that "there is a large body of evidence that maintaining healthy vitamin C levels can have a protective function against age-related cognitive decline and Alzheimer's disease."

Vitamin C foods
Meeting the newly recommended RDA of 200 mg per day of vitamin C is not difficult to achieve. Here are just a few foods high in vitamin C, with estimated number of milligrams:

  • Papaya (1): 187 mg
  • Bell peppers (1 cup, raw): 117 mg
  • Orange juice (1 cup): 100 mg
  • Broccoli (1 cup chopped): 100 mg
  • Grapefruit (1 cup sections): 85 mg
  • Strawberries (1 cup): 85 mg
  • Orange (1 medium): 70 mg

Frei noted that "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." The addition of just a few tasty fruits and vegetable servings per day could help you achieve the higher RDA for vitamin C.

Oregon State University
Du J et al. Ascorbic acid: chemistry, biology and the treatment of cancer. Biochim Biophys Acta 2012 Jun 20
Harrison FE. A critical review of vitamin C for the prevention of age-related cognitive decline and Alzheimer's disease. Journal of Alzheimer's Disease 2012; 29(4): 711-26
Juraschek SP et al. Effects of vitamin C supplementation on blood pressure: a meta-analysis of randomized controlled trials. American Journal of Clinical Nutrition 2012 May; 95(5): 1079-88
Pfister R et al. Plasma vitamin C predicts incident heart failure in men and women in European Prospective Investigation into Cancer and Nutrition-Norfolk prospective study. American Heart Journal 2011 Aug; 162(2): 246-53

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