Vitamin C

Vitamin C is a micronutrient which is present in some food and is necessary for normal human function. A severe deficiency of vitamin C causes scurvy, a disease characterised by connective tissue disorders, impaired wound healing, bleeding gums and other serious symptoms.

The effect of vitamin C deficiency on the immune system is unclear, with contradictory evidence. There is reason to believe that vitamin C may play a significant role in cellular immunity.

In the test tube, very high concentrations of vitamin C can prevent HIV from infecting new cells and prevent the activation and replication of HIV in dormant infected cells. Vitamin C also dramatically reduced the formation of syncytia, clumps of dysfunctional T-cells which form around an HIV-infected T-cell in the test tube. Syncytia tend to appear more frequently when CD4 cell counts are falling rapidly, and it has been theorised that their appearance may indicate an increased chance that AIDS-related illnesses will develop. In vitro vitamin C has also been shown to inactivate other viruses such as herpes simplex, rabies and tobacco mosaic virus.

As well as these anti-viral effects, vitamin C is required by phagocytes (immune cells which fight bacterial and fungal infections). High levels of vitamin C assist phagocytes in identifying and destroying Candida and other fungi, suggesting that vitamin C may play a role in protection against fungal infections. Vitamin E is thought to to play a similar role, and has been shown to reduce the level of such infections in the elderly, who often have poor immune function.

The presence of vitamin C is also crucial to the effectiveness of enzymes in the liver which remove toxins from the body.

Vitamin C is also known as ascorbic acid or ascorbate.

Current use

Most of the evidence that taking supplements of vitamin C can delay progression or improve survival in people with HIV is based mainly on the test tube studies demonstrating its anti-HIV effects. These studies also suggest that vitamin C's in vitro activity against HIV is enhanced when it is used in combination with N-acetyl cysteine (NAC).

One study has found evidence that people taking vitamin C and vitamin E showed a trend towards reduced viral load after three months of treatment, although the result did not reach statistical significance.

The researcher who demonstrated vitamin C's anti-HIV effects in vitro believes that doses of at least 10g per day are needed in order to produce the viral inhibition he observed in his laboratory studies. However, high doses of vitamin C cause diarrhoea, a sign that the gut can absorb no more of the vitamin. Bowel tolerance varies from one person to another, and is believed to depend upon the ability of the individual to metabolise the vitamin. People with acute illnesses such as Pneumocystis pneumonia (PCP) are reported to have tolerated doses of 60 to 150g per day before the onset of diarrhoea.

Other researchers fear that doses much higher than 10-12g/day may have unforeseeable long-term side effects and that doses higher than this should be used only in the case of an acute infection, and only then under medical supervision. One group found that a 500mg daily supplement of vitamin C may act as a pro-oxidant, causing cell damage. Another group reviewed data from biochemical, clinical and epidemiological research and found that a dose of 90 to 100mg vitamin C per day is required to reduce chronic disease in non-smokers. Based on this data, they suggest a recommended daily intake of 120mg vitamin C per day.1

Vitamin C at doses above 1g a day has been shown to reduce indinavir (Crixivan) levels, so vitamin C should not be taken at high doses alongside indinavir.

High doses of vitamin C may cause kidney stones due to excess acidity. It is possible to test for susceptibility to kidney stones by doing tests for oxalic acid excretion in urine at different levels of vitamin C use. If oxalic acid excretion increases as the dose increases, an individual is vulnerable, but protection against elevated levels of oxalic acid is provided by taking 50 to 100mg vitamin B6 and a magnesium supplement alongside vitamin C.

A more serious reaction to high doses of vitamin C may be experienced by people who suffer from glucose-6-phosphate dehydrogenase deficiency. This deficiency is found in about 10% of black Americans and is even more common in Africans and people of Mediterranean and Middle Eastern origin. In one case a man receiving massive doses of vitamin C intravenously suffered a shock reaction in which his red blood cells ruptured. Oral vitamin C is not thought to be capable of triggering such a haemolytic shock.

A group of Finnish researchers reported that vitamin C solution may help herpes lesions to heal.2 A solution of 100mg vitamin C dissolved in 3ml water was pressed onto herpes sores on the lips using a cotton wool pad three times at 30 minute intervals. Among 46 participants, vitamin C recipients reported significantly faster healing of sores and a reduced rate of scabbing or swelling compared with those given a placebo. However, this trial was conducted among HIV-negative, not HIV-positive, people.

Taking it

Unlike virtually every other animal and plant species, humans cannot manufacture sufficient quantities of vitamin C for themselves. Instead, it has to be obtained from food. Vitamin C is found naturally in many foods including citrus fruits, green vegetables, liver and kidney.

Different forms of vitamin C are available. Ascorbic acid is a highly acidic powder, which can cause stomach pain and discomfort when taken in large doses. Calcium ascorbate is a less acidic form of vitamin C buffered with calcium which tastes so unpleasant it makes some people sick. It can be dissolved in fruit juice or any liquid to mask the taste. Tablets are a much more expensive way of taking the vitamin in large quantitities, but some manufacturers claim that one form of tableted ascorbate, ester-C, yields three times as much vitamin C in the body i.e. a 1g tablet yields 3g when metabolised.

If stopping vitamin C, the dose use should be reduced gradually to reduce the risk of so-called 'rebound scurvy'.


  1. Carr AC et al. Toward a new recommended dietary allowance for vitamin C based on an antioxidant and health effects in humans. Am J Clin Nutr 69: 1086-1107, 1999
  2. Hovi T et al. Topical treatment of recurrent mucocutaneous herpes with ascorbic acid-containing solution. Antiviral Research 27: 263-270, 1995

Community Consensus Statement on Access to HIV Treatment and its Use for Prevention

Together, we can make it happen

We can end HIV soon if people have equal access to HIV drugs as treatment and as PrEP, and have free choice over whether to take them.

Launched today, the Community Consensus Statement is a basic set of principles aimed at making sure that happens.

The Community Consensus Statement is a joint initiative of AVAC, EATG, MSMGF, GNP+, HIV i-Base, the International HIV/AIDS Alliance, ITPC and NAM/aidsmap

This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.

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