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Vital Vitamin C

 

Vitamin C is a water-soluble vitamin that has a number of biological functions.

Where is it found?
Broccoli, red peppers, currants, Brussels sprouts, parsley, potatoes, citrus fruit, and strawberries are good sources of vitamin C.

Who is likely to be deficient?
Although scurvy (severe vitamin C deficiency) is uncommon in Western societies, many doctors believe that most people consume less than optimal amounts. Fatigue, easy bruising, and bleeding gums are early signs of vitamin C deficiency that occur long before frank scurvy develops. Smokers have low levels of vitamin C and require a higher daily intake to maintain normal vitamin C levels. Women with preeclampsia have been found to have lower blood levels of vitamin C than women without the condition. Women who have lower blood levels of vitamin C have an increased risk of gallstones.

People with kidney failure have an increased risk of vitamin C deficiency. However, people with kidney failure should take vitamin C only under the supervision of a doctor, as excessive vitamin C intake can be toxic in people who cannot excrete it properly.

How much is usually taken?
The recommended dietary allowance (RDA) for vitamin C in nonsmoking adults is 75 mg per day for women and 90 mg per day for men. For smokers, the RDAs are 110 mg per day for women and 125 mg per day for men. Most clinical vitamin C studies have investigated the effects of a broad range of higher vitamin C intakes (100 to 1,000 mg per day or more), often not looking for (or finding) the “optimal” intake within that range. In terms of heart disease prevention, as little as 100 to 200 mg of vitamin C appears to be adequate.4 Although some doctors recommend 500 to 1,000 mg per day or more, additional research is needed to determine whether these larger amounts are necessary. Some vitamin C experts propose that adequate intake be considered 200 mg per day because of evidence that the cells of the human body do not take up any more vitamin C when larger daily amounts are used.

Some scientists have recommended that healthy people take multi-gram amounts of vitamin C for the prevention of illness. However, little or no research supports this point of view and it remains controversial. Supplementing more results in an excretion level virtually identical to intake, meaning that consuming more vitamin C does not increase the amount that remains in the body. On the basis of extensive analysis of published vitamin C studies, researchers at the Linus Pauling Institute at Oregon State University have called for the RDA to be increased, but only to 120 mg. This same report reveals that “. . . 90 to 100 mg vitamin C per day is required for optimum reduction of chronic disease risk in nonsmoking men and women.” Thus, the multiple gram amounts of vitamin C taken by many healthy people may be superfluous.

The studies that ascertained approximately 120–200 mg daily of vitamin C is correct for prevention purposes in healthy people have typically not investigated whether people suffering from various diseases can benefit from larger amounts. In the case of the common cold, a review of published trials found that amounts of 2 grams per day in children appear to be more effective than 1 gram per day in adults, suggesting that large intakes of vitamin C may be more effective than smaller amounts, at least for this condition

Are there any side effects or interactions?
Some people develop diarrhea after as little as a few grams of vitamin C per day, while others are not bothered by ten times this amount. A review of the available research concluded that high intakes (2 to 4 grams per day) are well-tolerated by healthy people. However, intake of large amounts of vitamin C can deplete the body of copper—an essential nutrient, so people using higher intakes of vitamin C should also supplement with copper, or take a multivitamin that contains copper.

Vitamin C increases iron absorption and should be avoided by people with iron-overload diseases (for example, hemochromatosis, hemosiderosis). People with the following conditions should consult their doctor before supplementing with vitamin C: glucose-6-phosphate dehydrogenase deficiency, iron overload (hemosiderosis or hemochromatosis), history of kidney stones, or kidney failure.

As vitamin C may react with certain medicines, people undergoing treatment should consult with their doctor or pharmacist before adding the nutrient to their self-care regimen.

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