Millions of U.S. cancer survivors take vitamin supplements. However, there is little evidence that supplements help, and worries that some may actually fuel the disease.
A review of 32 studies conducted between 1999 and 2006 found that 64 percent to 81 percent of cancer survivors take extra vitamins or minerals (excluding multivitamins). But little is known about how megadoses of vitamins affect cancer.
A 1995 report showed that cancer cells in a petri dish thrive in the presence of vitamin C, and subsequent studies have suggested that vitamin C supplements may lower survival rates. A study of vitamin E showed patients with cancers of the head and neck who took supplements increased their risk for developing a second cancer.
The American Cancer Society says use of vitamins and supplements during cancer treatments should be avoided.
* New York Times February 6, 2008