Vitamin C


Vitamin C, also called ascorbic acid, is powerful water-soluble antioxidant that is vital for the growth and maintenance of all body tissues. Though easily absorbed by the intestines, vitamin C cannot be stored in the body, and is excreted in the urine within two to four hours of ingestion. Humans, along with apes and guinea pigs, are the only species on the planet incapable of synthesizing vitamin C, and must therefore have access to sufficient amounts from adequate dietary sources or supplements in order to maintain optimal health.

One of vitamin C’s most vital roles is in the production of collagen, an important cellular component of connective tissues, muscles, tendons, bones, teeth and skin. Collagen is also required for the repair of blood vessels, bruises, and broken bones.

This easily destroyed nutrient also protects us from the ravages of free radicals, dangerous unpaired oxygen fragments that are produced in huge numbers as a normal byproduct of human metabolic processes. Left unchecked, free radicals can roam the body, destroying cell membranes on contact and damaging DNA strands, leading to degenerative diseases and contributing to accelerated aging. The antioxidant activity of vitamin C can also protect us from the damaging effects of air pollution and radiation, and aid in preventing cancers. Vitamin C also inhibits the conversion of nitrites, chemicals found in foods and processed meats, into nitrosamines, dangerous cancer causing compounds that can lead to cancers of the stomach, bladder, and colon.

Vitamin C helps regulate blood pressure, contributes to reduced cholesterol levels, and aids in the removal of cholesterol deposits from arteriel walls, thus preventing atherosclerosis. Vitamin C also aids in the metabolization of folic acid, regulates the uptake of iron, and is required for the conversion of the amino acids L-tyrosine and L-phenylalanine into noradrenaline. The conversion of tryptophan into seratonin, the neurohormone responsible for sleep, pain control and well being, also requires adequate supplies of vitamin C.

A deficiency of ascorbic acid can impair the production of collagen and lead to joint pain, anemia, nervousness, retarded growth, reduced immune response, and increased susceptibility to infections. The most extreme form of vitamin C deficiency is called scurvy, a condition evidenced by swelling of the joints, bleeding gums, and the bursting, or hemorrhaging, of tiny blood vessels just below the surface of skin. If untreated scurvy is fatal. Before the discovery of lemons and limes as convenient sources of ascorbic acid, seafarers setting out on long ocean voyages could expect to lose up to two-thirds of a ships crew to scurvy. In acknowledgement of the the historical import of this well known and dreaded deficiency disease, in latin, the word ascorbic means “without scurvy”.

A recent important epidemiologic study showed that men who took vitamin C supplements lived, on average, 6 years longer than men who relied on normal dietary sources of vitamin C. This increase in life span seems to be due to a sharp reduction in heart disease. It has been estimated that if the epidemiology study is correct and everyone took just several hundred milligrams of vitamin C a day, it would save 100,000 lives and $100 billion a year in health care costs in the U.S. The recommended daily intake for vitamin c is 60 milligrams, but most health care professionals recognize that this tiny amount is barely enough to prevent the onset of scurvy, let alone confer any of the many well documented benefits of this amazing nutrient. Based on countless medical studies the therapeutic intake of ascorbic acid can be said to safely range from 500 to 4000 milligrams per day. Since this water-soluble vitamin is completely excreted from the body within 2 to 4 hours, and since the idea is to maintain stable serum levels for best results, the desired total daily dose should be divided into three separate doses and be taken throughout the day.

Foods highest in vitamin C include citrus fruits, potatoes, peppers, green leafy vegetables, tomatoes, and berries. Vitamin C is also available as a supplement in a wide range of forms such as pills, tablets, powders, wafers, and syrups. Generally doses range from 500 milligrams to 5000 milligrams depending upon the delivery system. Vitamin C activity is enhanced when taken with natural bioflavanoids such as hesperidn and rutin. Ascorbic acid works synergistically with vitamin E, meaning that both nutrients work more effectively together to extend their antioxidant effects. Ascorbyl palmitate is a fat soluble form of vitamin C that is available only in supplement form. It is a very powerful antioxidant that works to protect fats from peroxidation, and it can be stored in the body in small amounts. Ascorbyl palmitate works best when taken in combination with ascorbic acid.

The topical application of vitamin C inhibits tumor promotion in mouse skin, according to a recent study. Moreover, ascorbyl palmitate, the fat-soluble form of vitamin C, was found to be at least 30 times more effective than water-soluble vitamin C in tumor reduction in the presence of a known tumor promoter.

While the study also demonstrated that it was possible to increase levels of ascorbic acid in the skin via dietary means, that increase did not result in tumor inhibition in this study Only topically applied vitamin C (both the watersoluble and, especially, the fat-soluble forms) resulted in enhanced protection. Mice, unlike humans, can synthesize vitamin C in their bodies. The mice did not do better at the lowest dose of vitamin C, which apparently down-regulated their natural production. At higher doses, however, supplemented mice did better than unsupplemented mice. The ability to inhibit tumor-promotion in skin via dietary supplemen-tation with ascorbyl palmitate is under investigation. (Smart RC, Crawford CL. Effect of ascorbic acid and its synthetic lipophilic derivative ascorbyl palmitate on phorbol ester-induced skin-tumor promotion in mice.Am J Clin Nutr. 1991;54:1266S-12735.)

Mice that had high dietary intakes of vitamin C (ascorbic acid) and were subjected to ultraviolet (UV) light had fewer malignant skin lesions than those with lower levels of vitamin C. In a 20-week study, those mice receiving the lowest levels of dietary ascorbate developed serious malignant lesions at five times the rate of those mice fed the highest amounts of supplemental ascorbate. With a high statistical correspondence, the study showed that vitamin C was able to delay the formation of tumors induced by UV light. No toxic side effects of any sort were found with regard to the levels of vitamin C. (Pauling L. Effect of ascorbic acid on incidence of spontaneous mammal tumors and UV-light-induced skin tumors in mice. Am J Clin Nutr. 1991;54:1252S-1255S.)

While generally nontoxic, even in very large amounts, consuming vitamin C in large doses can lead to oxalic acid and uric acid stone formation unless consumed with plenty of water and supplemented with extra magnesium and vitamin B6. Taking large doses without slowly working up to the desired level can also cause temporary side effects such as diarrhea and skin rashes.

VITAMIN C AND HIV SUPPRESSION: Suppression of human immuno-deficiency virus (HIV) was found to take place in the presence of vitamin C. The near two-fold inhibition of HIV growth in Vitro required a continuous presence of non-cytotoxic amounts of either ascorbic acid or calcium ascorbate. When vitamin C was combined with NAC (N-acetyl L-cysteine), the result was a synergistic eight-fold inhibition of HIV replication. NAC is a mucolytic agent (mucous liquefier) that is structurally and functionally related to L-cysteine. This trial suggests the potential for the antiviral activity of vitamin C, especially in combination with thiol compounds such as L-cysteine, for improved control of HIV infections. (Harakeh S, Jariwalla R.J. Comparative study of the anti-HIV activities of ascorbate and thiol-containing reducing agents in chronically HlV-infected cells. Am J Clin Nutr 1991;54:S1231-1235S.)

Submit a comment or feedback about this article: