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HSR's (Health Supplement Retailer) Guide to Vitamins
Vitamin C
Vitamin C cures the world's oldest known nutritional deficiency disease, scurvy. It was first isolated by Albert Szent-Gyorgyi in 1928 from pork adrenal glands and called hexuronic acid. In 1933, its chemical structure was established. It was successfully synthesized, and the name was changed to ascorbic acid.
Humans are one of the few species that cannot manufacture vitamin C. We must depend on our diet, or nutritional supplements, as the source of this
vitamin. Vitamin C exists in nature in both its reduced form, I-ascorbic acid, and in its oxidized form, I-dehydroascorbic acid. L-ascorbic acid is the most active form. However, in the body they convert back and forth to each other in a reversible equilibrium, and both prevent scurvy. Buffered vitamin C refers to the sodium, calcium, magnesium and potassium ascorbate salts. These forms of vitamin C are less acidic and may be less likely to cause gastric irritation when taken in higher doses.
Vitamin C is a water-soluble vitamin that is stored in many tissues throughout the
body, but the adrenal glands contain the highest concentration. It is easily absorbed in the small intestine. There are no known toxicities associated with vitamin C, though large doses may interfere with tests to determine occult blood in the stool and tests to monitor blood glucose levels in diabetics.
Sub-clinical deficiencies of vitamin C are common. Deficiency symptoms include capillary fragility, muscular weakness, easy bruising, gums that bleed easily, poor wound healing, anemia, poor appetite and growth, and tender, swollen joints. Hemorrhage and nonspecific bleeding are also indications, and researchers have suggested testing for vitamin C
deficiency in diagnosing nonspecific bleeding in surgical patients.' Stressful situations (both physical and emotional) also tend to deplete the body's stores of vitamin C quickly.
Diarrhea can occur due to large doses or an overdose of vitamin C, and can generally be controlled by lowering the dose of vitamin C until the diarrhea no longer occurs. Also, approximately 15 percent of people taking moderately high doses of vitamin C experience abdominal gas, bloating and cramping. The mineral ascorbates such as calcium or magnesium ascorbate are not acidic and may solve this problem.
Functions in the Body/Clinical Applications
Vitamin C has myriad activities in the body. It is an antioxidant,
neutralizing free radicals and regenerating the antioxidant vitamin E. It has enzyme activity, as it is involved in oxidation-reduction reactions, energy production, tyrosine metabolism, reduction and storage of iron, and the activation of folic acid. It is essential in the synthesis of collagen and elastin, the major structural components of skin, tendons, bone matrix, blood vessels and connective tissues. This may contribute to its ability to increase wound healing, It increases production of white blood cells, levels of antibodies and production of interferon. It is also required for the synthesis of the body's main stress response hormones in the adrenal glands, including epinephrine, norepinephrine, cortisol and histamine. Stresses, such as fever, burns, exposure to cold, physical trauma, fractures, high altitude and radiation, all require larger doses of vitamin C.
With such a variety of activities, it also has many clinical applications:
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Allergies: Vitamin C's antihistamine activity helps reduce allergy symptoms? It has also been hypothesized that the antioxidant and free radical scavenging activity of vitamin C may reduce the inflammatory or hypersensitivity responses in the body?
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Asthma: Evidence shows that low vitamin C intake is a risk factor for asthma." Though not well defined, multiple therapeutic reviews and meta-analyses have evaluated the role of vitamin C in the treatment of asthma.
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Atherosclerosis: Evaluation of an association between vitamin C and atherosclerosis has been studied for decades and continues to this day. Studies have noted the association between low levels of vitamin C and the presence of various forms of atherosclerotic disease?-' but a link to myocardial infarction is questioned." In one study, vitamins C and E demonstrated retardation of the early progression of transplant-related coronary arteriosclerosis.
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Cancer: A large meta-analysis and epidemiological studies have shown that vitamin C along with other dietary vitamins reduces the risk of many different types of cancers, especially those along the digestive tract.
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Cataracts: Long-term vitamin C supplementation substantially reduced the risk of developing cataracts? In fact, 158 patients were followed for three years, it was found that daily use of beta-carotene, vitamin C and vitamin E demonstrated a small deceleration in the progression of age-related cataracts.
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Cervical dysplasia: Women with cervical dysplasia were found to
hav low levels of vitamin C.
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Cholesterol lowering: Vitamin C has demonstrated an ability to increase HDL levels and has prevented the oxidation of LDL cholesterol? However,
there has been some debate regarding the clinical impact of using antioxidants such as vitamin C in conjunction with standard Western
medical practices. A study involving 153 patients with coronary artery disease evaluated the clinical impact of antioxidant supplementation,
including vitamin C, vitamin E, beta-carotene and selenium, on people with low HDL levels in an effort to improve the HDL-to-LDL ratio. Investigators noted that antioxidant use apparently blunted the beneficial impacts of pharmaceuticals in improving the ratio?
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Common cold: Analysis of 14 placebo-controlled trials showed a 35-percent average reduction in the duration of colds and a decrease in the severity of symptoms when using vitamin C at dosages above RDA levels.
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Diabetes: Most diabetics have a greater need for vitamin C.
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HIV: Preliminary research and observation has noted that extremely high doses, 50 g/d to 200 g/d, can suppress the symptoms of the disease and can markedly reduce the tendency for secondary infections. In order to assess the immunological and virological effects of short-term, high-dose antioxidant treatment in patients with HIV infection, eight patients with HIV infection were given high doses of N-acetylcysteine (NAC) and vitamin C for six days. Though further study is warranted, the five patients with the most advanced immunodeficiency did experience a rise in CD4+ lymphocyte count, a reduction in HIV RNA plasma level and improvements in other measures?
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Immunity: Using supplements with 1 g/d to 3 g/d provides a variety of immunostimulatory effects.
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Osteoporosis: Bone loss and decreases in bone mineral density are inevitable as we age. It is important to slow this process, maintain strong healthy bones and thus decrease the risk of bone fractures. According to the National Osteoporosis Foundation, over half of Americans older than 50 have low bone mineral density, and 80 percent of those are women. Especially when used with other therapies, vitamin C supports bone mineral density.
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Wound healing: Overall, studies identify a possible role for the vitamin in wound healing, and some support the role of vitamin C in properly caring for and treating healing wounds.
Reprinted from the November 2002 issue of HSR's Guide to
Vitamins
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