Vitamin C

Vitamin C is also known as ascorbic acid.

What does vitamin C do?

Vitamin C is a water-soluble vitamin that functions as a powerful antioxidant. Acting as an antioxidant, one of vitamin C’s important functions is to protect LDL cholesterol from oxidative damage. (Only when LDL is damaged, does cholesterol appear to lead to heart disease, and vitamin C may be the most important antioxidant protector of LDL.)

Vitamin C is needed to make collagen, the “glue” that strengthens many parts of the body, such as muscles and blood vessels. Vitamin C also plays important roles in wound healing and as a natural antihistamine. This vitamin also aids in the formation of liver bile and helps to fight viruses and to detoxify alcohol and other substances.

Although vitamin C appears to have only a small effect in preventing the common cold, it reduces the duration and severity of a cold. Large amounts of vitamin C (e.g., 1–8 grams daily) taken at the onset of a cold episode shorten the duration of illness by an average of 23%.

Recently, researchers have shown that vitamin C improves nitric oxide activity.³ Nitric oxide is needed for the dilation of blood vessels, potentially important in lowering blood pressure and preventing spasm of arteries in the heart that might otherwise lead to heart attacks. Vitamin C has reversed dysfunction of cells lining blood vessels. The normalization of the functioning of these cells may be linked to prevention of heart disease.

Evidence indicates that vitamin C levels in the eye decrease with age and that supplementing with vitamin C prevents this decrease, leading to a lower risk of developing cataracts. Healthy people have been reported to be more likely to take vitamin C and vitamin E supplements than those with cataracts in some, but not all, studies.

Vitamin C has been reported to reduce activity of the enzyme aldose reductase in people. Aldose reductase is the enzyme responsible for accumulation of sorbitol in eyes, nerves, and kidneys of people with diabetes. This accumulation is believed to be responsible for deterioration of these parts of the body associated with diabetes. Therefore, interference with the activity of aldose reductase theoretically helps protect people with diabetes.

There is some speculative evidence that vitamin C might help prevent gallstones; however, supportive evidence remains preliminary.

Where is vitamin C found?

Broccoli, red peppers, currants, Brussels sprouts, parsley, rose hips, acerola berries, 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 nutritionally oriented 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.

How much is usually taken?

Doctors of natural medicine often recommend 500–1,000 mg per day. Most research uses levels that do not exceed 1,000 mg per day. However, even greater levels (up to 10,000 mg per day) are not uncommon. In terms of heart disease prevention, as little as 100–200 mg of vitamin C might be adequate.

In contrast, current vitamin C researchers believe that 200 mg per day gets close to raising blood levels in healthy people about as high as they will go, and that supplementing more results in an excretion level almost identical to intake, meaning that more vitamin C does not stay in the body. This suggests that levels above 200 mg per day may prove to be superfluous for healthy people. The same kinds of studies that have ascertained that 200 mg is approximately correct for healthy people have not yet been done with sick individuals.