Vitamin C, also known as ascorbic acid, has more functions than almost any other vitamin. A water-soluble nutrient, vitamin C is most known for its antioxidant properties, capable of neutralizing free radicals and minimizing oxidative damage. Vitamin C has more uses than the prevention of scurvy, although many people still believe that that is its only use. It has been successfully used in a wide variety of conditions in humans and animals.
Vitamin C is an unusual vitamin, because almost all species make their own, except humans, apes, guinea pigs and some species of bats. Scientists believe that through evolution we somehow lost the ability to synthesize an enzyme required to manufacture it.
Vitamin C’s function as an antioxidant may help delay or prevent the development of cataracts. The nutrient may well be valuable because long-term exposure to ultraviolet radiation and oxidative trauma resulting in cell damage to the lens of the eye are thought to be the primary causes of cataract formation. Ascorbic acid has also been found to lower the risk of diabetic retinopathy, according to a recent study in the American Academy of Ophthalmologyjournal. And in 2001, the National Eye Institute, one of the divisions of the United States National Institutes of Health proved that 500 mg of Vitamin C daily, as part of a high-dose regimen of specific antioxidants and minerals, reduced the rate of progression of an irreversible blinding eye disease known as macular degeneration.
Ascorbic acid strengthens and prevents cellular damage, and has the ability to detoxify lead, mercury, cadmium and other environmental toxins. It is used to aid in the treatment and prevention of the common cold, as well as prevent many types of viral and bacterial infections. It also has been found to decrease levels of histamine, a chemical released by the body that can trigger an inflammatory response. Another important function of vitamin C is in the manufacture and release of neurotransmitters, compounds which allow nerve impulse transition between nerve axons.
One of ascorbic acid’s main functions is in the production of collagen, the building block of tissues. Many nutritional studies have shown ascorbic acid to support and protect skin, tendons, bones, blood vessels, organs and muscles. Vitamin C also assists in healing wounds and burns and can accelerate healing after surgical procedures.
Vitamin C has been found to guard against cancer-producing agents and can help to inhibit the production of nitrosamines — potentially carcinogenic compounds commonly found in processed foods. Experiments have shown that vitamin C can provide considerable protection against the effects of harmful chemicals associated with drinking and smoking. Ascorbic acid is used up in destroying these substances, so it is not surprising that smokers and alcohol drinkers have much lower vitamin C serum levels than those who refrain from these behaviors.
A large number of studies have investigated the role of vitamin C in cancer prevention. In a cancer study by Linus Pauling and Ewan Cameron, 100 terminal cancer patients who took 10 grams of vitamin C a day lived an average of over 200 days compared to only 50 days for the control terminal cancer patients. Another study in the American Journal of Clinical Nutrition shows that the epidemiologic evidence of a protective effect from vitamin C on non-hormonal cancers is strong.
Of the many functions that vitamin C has in the body, several are associated with the health of the heart and blood vessels. Ascorbic acid helps make and stabilize nitric oxide, a signaling molecule that helps relax arteries, and many health studies have shown that taking 500-2000 milligrams lowered blood pressure in people with hypertension. Equally important, vitamin C helps to build the tough connective proteins that are found in the blood vessel walls of the circulatory system. It also assists in lowering certain levels of fats in the blood while increasing levels of protective high-density lipoproteins (HDL).
The First Health and Nutrition Examination Survey (NHANES I) Epidemiologic Follow-up Study found that “the risk of death from cardiovascular disease was 42% lower in men and 25% lower in women who consumed …a total vitamin C intake of about 300 mg/day.” And results from the Nurses’ Health Study (NHS) followed more than 85,000 women over 16 years, and found that higher vitamin C intakes may be cardio-protective
Vitamin C has also been shown to be helpful in assisting people with weight loss. Researchers in the Department of Nutrition at Arizona State University found that participants who had a low blood concentration of vitamin C burned 25 percent less fat than those who had sufficient amounts of vitamin C in their body. Scientists think this may be because ascorbic acid assists in the production of carnitine, which helps facilitate the oxidation of fatty acids.
The U.S. RDA is currently set at 75 mg per day for women and 90 mg per day for men. Many experts feel that this amount is much too low. Recent studies indicate that our RDA for vitamin C is the amount needed to prevent the manifestation of the worst symptoms of scurvy, rather than a level which would encourage ideal health. People who are exposed to tobacco, drugs, alcohol, or those under emotional or physical stress or who eat an unhealthy diet would require more.
Linus Pauling, the Nobel Prize winner who studied the effects of large doses of vitamin C on the common cold, flu and cancer, recommended an optimum intake of between 2 and 9 grams per day, but daily doses most often range from 500 milligrams to 4 grams.
The highest amounts of vitamin C can be found in citrus fruits, berries, strawberries, guava, kiwi, sweet peppers, Brussels sprouts, tomatoes, broccoli, parsley, and dark leafy greens.
In order to maximize vitamin C benefits, you must take vitamin C several times during the day to maintain adequate serum levels, due to the rapid excretion of this water-soluble vitamin.
The first signs of depletion include weakness, lethargy, and poor resistance to infection, followed by delayed wound healing, bleeding gums, anemia, bronchial infections, and a tendency to bruise easily. Severe deficiency includes anemia, shortness of breath, joint tenderness and swelling and tooth loss.
Vitamin C is considered to be non-toxic even at high levels. It may, however, inhibit the absorption of certain antidepressants and may also cause inaccurate readings in some medical diagnostic tests. Ascorbic acid can also reduce the efficacy of statin drugs. Very high doses can cause diarrhea, and stomach irritation can occur if large amounts of vitamin C are taken together with aspirin. Avoid using chewable supplements, as these have a tendency to damage tooth enamel.