Curcumin - some issues to consider

Curcumin is a yellow colouring agent found in the spice turmeric. It is curcumin that is responsible for the colour of curry. In Asia, extracts of turmeric have been used for centuries to treat inflammatory conditions such as arthritis. In the 1990s, researchers found that curcumin had anti-HIV activity in lab experiments with cells. As well, curcumin is supposed to have antioxidant properties and may impair the growth of lymphoma.

A closer examination of the data associated with curcumin suggests that, although this extract may have anti-HIV activity, its prolonged use in large doses (far greater than those found in curry recipes!) may not be appropriate in people with HIV/AIDS for a number of reasons.

First, curcumin appears to suppress the chemical messengers needed by the immune system (cytokines) to fight HIV and many of the infections seen in AIDS. At the same time, this plant extract appears to stimulate production of cytokines that further weaken the immune system.

Second, curcumin can block the growth of B-cells and, more important, T-cells. In people with HIV/AIDS, CD4+ and CD8+ cells appear to die faster than normal. Compounds that therefore impair the growth of T-cells - and possibly cause them to die prematurely - may accelerate HIV's destruction of the immune system.

Third, curcumin has historically been used to suppress inflammatory conditions such as arthritis. Drugs such as corticosteroids and low-dose cyclosporin can also produce similar benefits. However, prolonged use of corticosteroids can weaken the immune system's ability to fight infections. Indeed, in some experiments, curcumin's anti-inflammatory activity has been compared to that of the immune-suppressing drug cyclosporin. Clinical trials of cyclosporin in people with HIV/AIDS have not produced beneficial results.

Fourth, curcumin has antioxidant activity. This feature may make it attractive to people with HIV/AIDS because of their need for an increased intake of antioxidants. It appears, however, that curcumin should not be the antioxidant of first choice. The reason for this is that the body has specific biochemical needs for certain antioxidants such as vitamins C and E. As well, the body can make its own antioxidant enzymes using the amino acid cysteine and the minerals selenium, zinc, copper and manganese. Finally, some people may choose to take supplements of alpha-lipoic acid, an expensive antioxidant. Fulfilling the basic nutritional needs with antioxidants and the substances to make them should take priority over a compound for which there is no daily requirement.

Curcumin and the immune system

Study details
Researchers conducted experiments using curcumin and cells of the immune system such as macrophages and CD4+ cells. These cells, particularly macrophages, play an important role in helping the immune system recognize and fight many of the infections seen in AIDS. Some of the experiments also used mice.

Results
Exposing macrophages to tiny doses of curcumin blocked their ability to produce IL-12 in response to simulated attack by microbes. IL-12 helps CD4+, CD8+ and natural killer cells by stimulating their production of interferon-gamma (IFN-gamma). IFN-gamma is a cytokine that helps these cells fight viruses, certain bacteria and fungi. Without the stimulus of IL-12, the immune system would not be able to protect the body from these microbes.

Curcumin-treated macrophages caused CD4+ cells to produce increased amounts of IL-4. This cytokine weakens cellular immunity, which is the immune response needed to fight tuberculosis, cytomegalovirus, HIV and many other microbes. CD4+ cells that encountered curcumin-treated macrophages were also not able to produce much IFN-gamma.

Since curcumin is poorly absorbed from the intestine, technicians injected mice with a small amount of curcumin (500 micrograms). Again, CD4+ cells and macrophages taken from these mice were unable to produce much IL-12 and IFN-gamma.

This research team, as well as others, think that curcumin's ability to weaken cellular immunity may be useful in treating disorders in which the immune system attacks the body. Example of such conditions include

• Multiple sclerosis
• Inflammatory bowel syndrome
• Insulin-dependent diabetes
• Rheumatoid arthritis
• Psoriasis

When considered together, the results from this and other studies suggest that curcumin is not likely to help the immune systems of people with HIV/AIDS.

Curcumin, which is responsible for the yellow colour in curry, has anti-inflammatory activity. Researchers in Kentucky and South Korea have found that it has potential as a treatment for lymphoma.

Study details

Researchers conducted laboratory experiments on B- and T-cells as well as on several types of B-cell lymphomas.

Results

• Curcumin clearly impaired the growth of four types of B-cell lymphomas. This compound caused the tumour cells to undergo apoptosis (to commit suicide).
• Curcumin blocked the ability of B-cells to grow by 35 to 63 per cent.
• Curcumin also impaired the growth of T-cells by 31 to 72 per cent.

Suppressing the immune system

In light of these results, the researchers believe that, when taken in large doses, curcumin may be as powerful an immune-suppressant as the drug cyclosporin. Cyclosporin is given to organ transplant recipients to help prevent their immune systems from rejecting new organs. Given its potential to suppress the immune system, curcumin should be used with caution by people with HIV/AIDS.

Curcumin and T-cell suicide

Exactly how curcumin affects T-cell function is not clear from these experiments. Curcumin causes lymphoma cells to undergo apoptosis. It would be troubling if curcumin also triggered this process in T-cells.

Curcumin may have limited use as an anti-lymphoma agent. Perhaps tests in SIV-infected monkeys could establish whether or not high-dose curcumin should be tested in humans with lymphoma. The intestine does not absorb curcumin well, so people may take it with the drug piperine, an extract of black pepper that boosts absorption of curcumin when given to mice and humans.