Vitamin C supplements

Vitamin C supplements are used to treat and prevent many diseases and conditions. For some of these there is research evidence while for others the evidence is mainly anecdotal. Vitamin C supplement use appears to be associated with a lower risk of death in elderly people and vitamin C seems to enhance the beneficial effects of vitamin E. Researchers involved in a study published in 1996 found that those elderly people who took vitamin C and vitamin E supplements had a lower risk of death from any cause and also from both cancer and heart disease. Those taking vitamin E supplements had a 34 per cent lower risk, and those taking both vitamin C and vitamin E had a 42 per cent reduced risk.

Cardiovascular disease

The evidence from epidemiological studies, animal experiments and some clinical trials suggests that vitamin C supplements may protect against the development of cardiovascular disease. In the same study mentioned in the previous paragraph, those taking vitamin E supplements had a 47 per cent lower risk of death from heart disease and those taking both vitamin C and vitamin E had a 53 per cent reduced risk.

Vitamin C supplementsVitamin C may exert its protective effects by lowering total blood cholesterol and harmful LDL cholesterol and raising beneficial HDL cholesterol. Vitamin C also increases the production of prostacyclin, a prostaglandin which decreases the clumping of blood platelets and dilates blood vessels, therefore reducing the risk of heart disease, atherosclerosis and stroke.

High fat meals cause damage to artery linings, which may contribute to the development of atherosclerosis. Research published in 1997 suggests that taking the antioxidant vitamins C and E before a meal may help to prevent this damage. The study which was carried out at the University of Maryland School of Medicine involved 13 women and seven men with normal blood cholesterol levels. Once a week for three weeks, the subjects ate either a high fat meal, a low fat meal, a high fat meal after taking 1000 mg of vitamin C and 800 IU of vitamin E, or a low fat meal after taking the antioxidants. Before and after the meals, the researchers measured blood fat and cholesterol levels, blood pressure and heart rate in the subjects. They also used ultrasound to measure the dilation of an artery in the arm after release of a tourniquet which had been applied for five minutes. If the artery lining is functioning normally, it releases nitric oxide which causes dilation. The results showed that the high fat meal decreased artery lining function for up to four hours afterwards, whereas the low fat meal did not. This is probably due to oxidative stress caused by an accumulation of triglyceride-rich lipoproteins (blood fats). Vitamins C and E prevented this decrease in artery lining function.

A recent US study looked at the effect of either 2 g of vitamin C or a placebo on patients with coronary artery disease. In such patients the arteries leading to the heart are unable to open when the heart requires increased blood flow. Those patients given the vitamin C experienced expansion in their arteries while those given the placebo experienced no effect. Vitamin C has similar effects in those with high cholesterol and in those with chronic heart failure.

When blood is re-supplied to an organ from which it was previously cut off, oxidative damage can occur. This has been found in many types of surgery, for example in heart bypass operations. Vitamin C has also been shown to protect against this reperfusion injury.


Vitamin C needs are higher in smokers and several studies suggest that vitamin C may protect against smoking-related damage. It may help to decrease the smoking-related build-up of atherosclerotic plaque by limiting the amount of white blood cells that stick to artery walls. Vitamin C supplements may be helpful in restoring reduced plasma vitamin C concentrations in smokers. Like those with high cholesterol levels and coronary heart disease, the arteries of smokers have a reduced ability to dilate. Vitamin C supplements may counteract this impairment.

High blood pressure

Vitamin C may also be of benefit in the treatment of mild high blood pressure, another risk factor for heart disease and stroke. Some research suggests that vitamin C may have beneficial effects in lowering high blood pressure. Vitamin C supplements improve abnormal artery lining function in hypertensive people.

Cancer prevention

Vitamin C supplements may have a part to play in cancer prevention. Some research suggests that the risk of cancer is lower in those taking supplements. Vitamin C may exert its anticancer effects by acting as an antioxidant and shielding the genetic mechanism of the cell from damage that can lead to cancerous changes. Vitamin C may also strengthen the ability of the immune system to track down and destroy pre-cancerous cells. Vitamin C may exert its protective effects against some cancers by inhibiting the formation of toxic

compounds known as nitrosamines from nitrite food additives. These compounds are also found in cigarette smoke and are linked to an increased risk of stomach and lung cancers.

Stomach cancer

Supplements may be useful in helping to prevent stomach cancer. In a 1996 study, researchers gave 32 patients 500 mg of vitamin C twice daily for two weeks. Levels in gastric juices and gut tissues were increased, raising the pos- sibility of increased protection against free radicals.

A 1997 report in the journal, Cancer, suggests that vitamin C may inhibit the growth of Helicobacter pylori, a stomach bacterium that increases the risk of ulcers and stomach cancer. High concentrations of vitamin C inhibited the growth of bacteria in culture dishes and also in the stomachs of Mongolian gerbils, according to researchers at the International Medical Center of Japan in Tokyo. Vitamin C-rich diets have been found to decrease the risk of stomach cancer. This has been attributed to the antioxidant ability of vitamin C. However, vitamin E, which is also an antioxidant, does not inhibit the growth of Helicobacter pylori. This suggests that vitamin C may exert its protective effects through a biochemical mechanism. This research suggests the possibility of a safe, side effect-free alternative to antibiotics for the treatment of ulcers.

Vitamin C supplementsColon cancer

Vitamin C supplements have also been shown to have beneficial effects against the pre-cancerous changes which occur in colon cancer. In a 1992 study, 20 patients with colorectal cancer were given vitamins A, C, and E for six months and 21 patients with adenomas received placebo. The results showed that supplementation with vitamins A, C, and E was effective in reducing pre- cancerous abnormalities. Vitamin C supplements may also be beneficial in the treatment of prostate cancer.

Cancer treatment

Controversy surrounds the use of vitamin C in the treatment of cancer. The Nobel Prize winner, Linus Pauling and his colleagues have used vitamin C to improve survival times in cancer patients, but these results have not been repeated in other studies. Vitamin C may also benefit cancer patients who are undergoing radiation treatment by enabling them to withstand greater doses of radiation with fewer side effects.

Asthma and allergy

There is some evidence that vitamin C is of benefit in reducing the bronchial constriction and impaired breathing seen in asthma and allergic responses. This effect may be due to the antioxidant effect of vitamin C as oxidizing agents promote inflammation and can increase allergic responses. Vitamin C may also improve lung and white blood cell function and decrease respiratory infections and hypersensitivity reactions by reducing histamine levels. However, some studies do not support a beneficial role in vitamin C in asthma. Most studies have been short term and have assessed immediate effects of vitamin C supplementation. The effect of long-term supplementation with vitamin C is unclear.

According to researchers from the University of Washington, antioxidant vitamin supplements may help relieve the symptoms of asthma. The researchers measured the amount of breath expelled by the lungs in 17 asthma sufferers. The subjects took peak flow lung function tests while running on a treadmill and breathing in high levels of polluted air. In those asthmatics whose diets were supplemented with daily doses of 400 IU of vitamin E and 500 mg of vitamin C, an 18 per cent increase in peak flow capacity was seen.

In a 1997 study, 20 asthma patients underwent lung function tests at rest, before and one hour after receiving 2 g of oral ascorbic acid. They were then randomly assigned in a double-blind manner to receive 2 g of ascorbic acid or a placebo one hour before a 7-minute exercise session on a treadmill. Lung function tests were performed after an 8-minute rest. This procedure was repeated one week later, with each patient receiving the alternative medication. In nine patients, a protective effect on exercise-induced hyperreactive airways was seen.

Vitamin C supplementsImmunity

Vitamin C boosts immunity by increasing the production of B and T cells and other white blood cells, including those that destroy foreign micro-organisms. It also increases interferon levels and antibody responses and has antiviral and antibacterial effects. These effects lead to improved resistance against infections. Vitamin C has been shown to help the immune system recover from exposure to toxic chemicals. In a 1997 study, researchers studied the effect of vitamin C on the function of several immune cells (natural killer, T and B cells) in patients who had been exposed to toxic chemicals. Fifty-five patients were given buffered vitamin C in water at a dosage of 60 mg per kg body weight (around 4g for the average man). Twenty-four hours later, the researchers tested immune cell function. The results showed that natural killer cell activity

was enhanced up to ten-fold in 78 per cent of patients. B and T cell function was restored to normal.


Vitamin C supplements are likely to be useful in HIV-positive individuals as they have been shown to boost the immune system and prevent damage to nerves. However, caution should be used with very high doses as they can cause diarrhea. Vitamin C has been shown to inhibit HIV in the laboratory and may also kill HIV-infected cells.

Common cold

Vitamin C may reduce the duration of the common cold and also the severity of symptoms such as sneezing, coughing and sniffling. Its use as a cold treatment is controversial but it seems to have several effects, including reducing blood levels of histamine which can trigger tissue inflammation and a runny nose. It may also protect the immune cells and surrounding tissue from damaging oxidative reactions that occur when cells fight bacteria.

It is possible that the effects of supplementation are greater in those with low dietary vitamin C intake. In general, men have lower vitamin C levels than women. In four studies with British girls and women, vitamin C supplementation had no marked effect on common cold. However, in four studies involving British male schoolchildren and students, a reduction in common cold occurrence was found in groups supplemented with vitamin C.

Research suggests that vitamin C supplementation may be beneficial for people who do heavy exercise and who have problems with frequent upper respiratory tract infections. Three placebo-controlled studies have examined the effect of vitamin C supplementation on common cold occurrence in people under acute physical stress. In one study the subjects were school children at a skiing camp in the Swiss Alps; in another they were military troops training in Northern Canada; and in the third they were participants in a 90 km running race. In each of the three studies, a considerable reduction in common cold incidence in the group supplemented with vitamin C at levels of 600 mg to 1000 mg per day was seen.


Many studies show that vitamin C can protect against cataracts, possibly by reducing oxidative damage caused by ultraviolet light. Vitamin C may act to protect the lens of the eye from this damage and protect enzymes within the lens that remove oxidation damaged proteins.

In a study published in 1992, researchers at Harvard Medical School examined the link between dietary intake of vitamins C and E, carotene, and riboflavin and cataract extraction in over 50,000 women taking part in the Nurses Health Study. The results showed that the risk of cataract was 45 per cent lower among women who used vitamin C supplements for ten or more years.

Further results from this study reported in 1997 in the American Journal of Clinical Nutrition also suggests that vitamin C supplements taken for long periods can reduce the development of cataracts. Researchers from the US Department of Agriculture and Harvard School of Public Health examined the link between cataract development and vitamin C supplement use over a ten to 12 year period. The subjects were 247 Boston area nurses aged from 56 to 71. The researchers performed detailed eye examinations to determine the degree of opacity (clouding) of the lenses of the eyes of the subjects. Results showed that use of vitamin C supplements for over ten years was associated with a 77 per cent lower prevalence of early lens opacities and an 83 per cent lower prevalence of moderate lens opacities.

Vitamin C supplementsDiabetes

Increasing vitamin C intake may improve blood sugar regulation in diabetics. Vitamin C administration in pharmacological doses for four months in Type II diabetes has been shown to have beneficial effects on glucose and lipid metabolism, blood circulation and capillary fragility.

In a 1995 study the effect of magnesium and vitamin C supplements on metabolic control was assessed in 56 diabetics. The study involved a 90 day run-in period followed by two 90 day treatment periods, during which patients received 600 mg of magnesium and 2 g of vitamin C per day. The results showed that vitamin C supplementation improved glycemic control, fasting blood glucose, cholesterol and triglyceride levels.

High blood sugar levels in diabetes cause a compound known as sorbitol to be manufactured from glucose. This contributes to the progression of diabetic complications. Vitamin C has been shown to reduce levels of sorbitol in diabetics. I n a 58 day study carried out in 1994, researchers investigated the effect of two different doses of vitamin C supplements (100 or 600 mg) on young adults with Type I diabetes. The results showed that vitamin C supplementation at either dose normalized sorbitol levels in those with diabetes in 30 days. Vitamin C may also help to reduce capillary fragility, which also contributes to complications. The ability of the arteries to dilate is impaired in diabetics. Vitamin C supplements improve the response.

Skin protection

Vitamins C and E taken together may protect against sunburn. In a study published in 1998, German dermatologists found that people who took these vitamins had a higher threshold for sunburn reaction. The researchers tested ultraviolet sensitivity in two groups often Caucasian people by exposing a section of skin to UV light. Subjects in one of the groups then took 2 g of vitamin C and 1000 IU of vitamin E for eight days. The UV test was then re-done. Those taking the vitamins showed increased tolerance, particularly at higher UV doses. However, in comparison with the protection afforded by topical sunscreens, this level of protection is small.

Vitamin C-containing cosmetic skin creams such as Cellex-C have also become extremely popular in the last few years. They are designed to protect against pollutants and to promote healing.


Vitamin C is involved in cholesterol metabolism and deficiency may increase the risk of gallstones. In a 1998 study published in the Journal of Clinical Epidemiology, researchers in San Francisco found that vitamin C supplements reduced the prevalence of gall bladder disease by half in 2744 postmenopausal women who regularly drank alcohol. Supplement use was also associated with a 62 per cent decrease in gallstone removal. The supplements had no effect on those who did not drink.

Researchers involved in a 1997 study to test the effect of vitamin C supplements on gallstones analyzed blood fat levels, cholesterol metabolism, bile fat composition and cholesterol saturation in 16 gallstone patients. They then treated the patients with 500 mg of vitamin C four times a day for two weeks before surgery. Their findings indicated that vitamin C supplementation may also influence the conditions for cholesterol gallstone formation.


Strenuous exercise appears to increase the levels of free radicals in the body, increasing the risk of disorders in which oxidative damage play a part. As an antioxidant, vitamin C may help to prevent this damage. In a 1997 study researchers examined the effects of supplements on oxidative stress in athletes. They found that exercise-induced oxidative stress was highest when those involved in the study did not supplement with vitamin C.

Other uses

Vitamin C has also been used to treat constipation and to speed wound-healing. Recent research suggests that vitamin C may help to enhance the strength of perm in smokers.

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Other Vitamins:

Vitamin A
Beta carotene
Vitamin B6
Vitamin B12
Pantothenic acid
Vitamin C
Vitamin D
Vitamin E
Vitamin K