Vitamin C - Vitamins

Vitamin C

Vitamin C, also known as ascorbic acid, is a water-soluble, white crystalline that is essential for the formation of collagen and fibrous tissue; for normal intercellular matrices in teeth, bones, cartilage, connective tissue, and skin; and for the structural integrity of capillary walls. It aids in fighting bacterial infections, interacts with other nutrients, and has been shown to relieve emotional and environmental stress and depression and to protect the circulatory system from fat deposits. Vitamin C is a key factor in many immune functions as well, including white blood cell function, interferon levels, increasing antibody levels and response, and increasing the secretion of thymic hormones. Vitamin C has been used as part of aggressive treatment programs for people with AIDS, cancer, and other diseases in which optimizing immune function is a critical therapeutic goal.

Vitamin C is present in citrus fruits, tomatoes, berries, potatoes, and fresh, green, leafy vegetables such as broccoli, brussel sprouts, collards, turnip greens, parsley, and cabbage. Relative to other nutrients, it is one of the safest substances known.

Vitamin C is also available in tablets, extended-release capsules, oral solutions, and injections. Tablets and capsules are sold in most health food stores. Vitamin C injections are available only from a physician.

Vitamin C deficiency symptoms include shortness of breath, digestive difficulties, easy bruising, swollen or painful joints, nosebleeds, anemia, frequent infections, and slow healing of wounds. Conversely, while massive daily doses of vitamin C are not necessarily toxic, because the body expels what it cannot use, they can cause stomach upset and diarrhea.

Vitamin C and Cataracts.     Cataracts are caused, in part, by changes in proteins located in the eye, and research studies suggest that vitamin C can prevent these changes. In one study, reported in the July 1992 Environmental Nutrition, people who took several vitamin supplements, including vitamin C, had four times less risk of developing cataracts than those who took no supplements. Research on vitamin C's role in preventing cataracts is still inconclusive, however, as other antioxidant nutrients such as vitamin E and betacarotene help prevent cataracts as well.

Vitamin C and Cholesterol.     Studies have demonstrated that vitamin C lowers LDL (“bad”) cholesterol levels in the blood because it attacks free radicals-the highly unstable oxygen molecules that damage (or oxidize) body tissues and blood fats. The free radicals' effect on LDL is similar to what happens to a steak when it is exposed to the air too long: it oxidizes and turns brown. Scientists now think that vitamin C and other antioxidants prevent the oxidation process caused by free radicals. According to Jeffrey Frei, assistant professor of nutrition at Harvard School of Public Health, in the October 1991 issue of Prevention Magazine, “Vitamin C traps free radicals in the surrounding environment before they can attack the LDL particle. As long as there is vitamin C, free radicals cannot attack LDL because the C forms a very tight, protective shield around it.” Furthermore, vitamin C strengthens HDL cholesterol (the good form) by making it more resistant to free-radical damage. Lowering blood cholesterol levels is still the only proven way to reduce heart disease. As a result, many physicians now recommend foods rich in vitamin C, E, and betacarotene (such as fruits and vegetables) as a way of lowering cholesterol. In addition, many experts suggest that the current RDA for vitamins C and E may be too low, and that betacarotene (a form of vitamin A) should be added.

Vitamin C and Disease Prevention.     Many studies have shown that increased vitamin C intake can produce a number of beneficial effects, including reducing the risk of cancer, strengthening the immune system, protecting against the effects of pollution and cigarette smoke, enhancing wound repair, and increasing life expectancy.

Pauling first postulated the theory that moderate doses of vitamin C (250–1,000 mg) effectively prevented the spread of viral and bacterial infections, and that large doses of one gram or more may cure those infections.

A growing body of scientists now believes that vitamin C also reduces the risk of cancer. In 1991, Dr. Gladys Block, professor of nutrition at the University of California at Berkeley, reviewed more than 100 studies linking vitamin C or vitamin C-rich foods (primarily fruit) and cancer prevention. Block found that vitamin C's protection is most convincing for cancers of the throat, mouth, pancreas, and stomach. In an article in the American Journal of Clinical Nutrition , published in January 1991, she also suggested that vitamin C has a protective effect against cancers of the cervix, rectum, and breast. A 1992 National Cancer Institute study, reported in the July 6, 1992, issue of Cancer Weekly , found that the protective effect of vitamin C against breast cancer was as great, if not greater, than the effect of reducing saturated fat intake.

Vitamin C performs several functions that explain why it may be important in preventing cancer. It acts as an antioxidant that protects cells and tissues from damage caused by free radicals, significantly influences immune function, and may inhibit the spread of tumors. Vitamin C was directly associated with “a significant protective effect” against cancer in 33 out of 46 studies that Block analyzed. Several of the studies also showed a positive correlation between fruit intake and protection against cancer. However, while these studies indicate vitamin C “reduces the risk of cancer,” they do not prove that vitamin C “cures” it.

The importance of vitamin C-rich diets was further confirmed in a broad-based study of esophageal cancer in China. In 1983, blood samples were collected from 100 adults (aged 25–64 years), and then analyzed. Both men and women who took vitamin C had significantly lower death rates from esophageal cancer. Death rates for people who did not take vitamin C were more than three times higher, according to a June 1984 report by Wande Guo and others in Nutrition and Cancer .

Vitamin C levels (as ascorbic acid) also inhibit skin tumors. A 1992 study carried out at Duke University Medical Center strongly suggests that vitamin C protects the skin against ultraviolet A (UVA) and ultraviolet B (UVB) light exposure. This study, reported in the January 1992 Harvard Health Letter , concluded that vitamin C acts as an antioxidant and prevents UVA and UVB oxidative damage to collagen, elastin, proteoglycan, and cell membranes. Some scientists now think that vitamin C will eventually be shown to prevent premature aging, wrinkles, and skin cancer.

Vitamin C and Hypertension.     Medical surveys have found that people whose vitamin C levels are low tend to have high blood pressure. A recent study published in Environmental Nutrition found that 1,000 mg a day of supplemental vitamin C significantly reduced systolic blood pressure (the top number in a blood pressure reading) in a group of 20 women, 12 of whom had borderline hypertension.

Vitamin C and Increased Longevity.     Adding substantially larger amounts of vitamin C to ordinary diets may prolong life by lessening the risk of heart disease and cancer. A large U.S. survey conducted by the National Center for Health Statistics (NCHS) demonstrated a strong correlation between vitamin C intake and decreased mortality. Between 1971 and 1974, the NCHS collected extensive diet and nutrition information from 11,348 adults aged 25–74. Investigators at the UCLA School of Public Health subsequently reviewed the participants' estimated daily vitamin C intake and divided them into three groups: less than 50 mg; 50 mg or more from dietary sources; and 50 mg or more from food, plus regular vitamin C supplementation, usually in the form of pills containing several hundred milligrams.

For men with the highest vitamin C intake, the total number of deaths was 35% lower than predicted; mortality due to cardiovascular diseases was 42% lower, and cancer deaths were 22% less. Benefits were not as apparent for women in the high-C group: there was an overall drop in expected mortality of 10%, with a 25% decline in deaths caused by heart disease, and a 15% reduction in those due to cancer, according to a report published in the July 1992 issue of Environmental Nutrition . Many of the participants also took vitamins A and E, which act to block the oxidation of cholesterol and other molecules thought to play important roles in the development of cancer and heart disease. Although the UCLA study does not prove that vitamin C supplements will guarantee a longer life, the findings do suggest that substantial amounts of vitamin C provide greater protection against fatal diseases.