- New York, NY
- Tara Parker-Pope
- DelawareOnline (www.delawareonline.com)
Many cancer patients take a range of antioxidant vitamins in hope of improving their odds, but some research suggests the supplements may be doing more harm than good.
A report published in CA, an American Cancer Society medical journal, says cancer patients shouldn’t use antioxidants during radiation or chemotherapy because the supplements may reduce the effectiveness of treatment. Worse, some research suggests that antioxidants may actually feed cancers, protecting the very cancer cells patients are trying to attack. The news further clouds the role that vitamins play in promoting good health. Earlier this year, a major study showed that certain people who regularly take vitamin E supplements had a higher risk for heart failure. The notion that antioxidants may be harmful is likely to be upsetting and confusing to the large number of cancer patients gobbling down vitamins and supplements to help fight the disease. Studies show that as many as a third to half of cancer patients are taking antioxidants, vitamins and other supplements.
Antioxidants include beta carotene, lycopene and vitamins A, B, C and E, among others. In the body, antioxidants mop up rogue molecules called free radicals, which have the potential to cause extensive cell damage and are believed to play a role in heart disease, cancer and numerous other health problems. A substance that attacks free radicals would seem to battle cancer in theory. But the results of both lab and human studies of cancer and antioxidants have been mixed. One concern is that because chemotherapy treatments sometimes act against the cancer by producing free radicals, taking antioxidants could interfere with that effect.
Some lab studies have shown that antioxidants can improve the effectiveness of cancer treatments, such as a 1997 study that showed antioxidant supplements boosted chemotherapy used for colon cancer patients. Other lab studies raise questions about their use, however. For instance, a 1995 report in the Journal of Biological Chemistry showed that cancer cells in a petri dish actually absorb more vitamin C than normal cells, suggesting that vitamin C is better at protecting tumors than healthy tissues.
Until more is known, patients undergoing treatment should avoid high-dose supplements, concludes Gabriella M. D’Andrea, breast oncologist at Memorial Sloan Kettering Cancer Center and author of the CA article. In her review of the scientific evidence on use of antioxidant supplements to prevent or treat cancer, D’Andrea found a handful of human trials that showed supplements often don’t benefit cancer patients and may be causing harm. “We would love to find a nutrient or antioxidant that could be anticancer, but I think we need to be very cautious,” D’Andrea says.
For instance, two randomized trials of patients with advanced cancer found no benefit from vitamin C supplements and suggested that survival may have been worse in the vitamin group. Two large trials of smokers and former smokers found that beta carotene supplements appeared to increase lung cancer risk. Last year, the British medical journal Lancet published a study showing that antioxidants didn’t prevent gastrointestinal cancers and may have increased mortality risk. In a 2002 study of early-stage breast cancer patients undergoing treatment, some were prescribed large doses of vitamins, minerals and antioxidants. Results weren’t conclusive but suggested survival may be worse in the antioxidant users. A major study this year of patients at risk for heart disease showed high doses of vitamin E had no impact on risk of melanoma, prostate, lung, oral, colorectal or breast cancers, but they were linked with higher risk for heart failure. A separate vitamin E study showed head-and-neck-cancer patients who took the supplement increased their risk for developing a second cancer.
D’Andrea says a large human trial is needed to show the real impact vitamins and antioxidants have on cancer patients. The problem is that such trials are expensive, and it’s notoriously difficult to study supplements because dietary patterns vary so widely and issues like fat content and fruit and vegetable consumption may alter the way one supplement acts in different people. Certainly, none of this means cancer patients should never take vitamins or other supplements. Many cancer patients suffer nutrition problems and may be advised to take vitamins. The main concern is that patients discuss diet changes with their doctor.
“A lot of people think nutrients in any dose are harmless, but that may not be the case,” says Marji McCullough, nutritional epidemiologist for the American Cancer Society. “It’s probably prudent to say people should avoid taking large doses of any single supplement unless specifically recommended to do so from their doctor.”
Patients still may be able to help themselves by adopting a lifestyle of healthful eating and exercise. In May, researchers released the results of a study of 2,400 postmenopausal women with early-stage breast cancer. The study showed that a low-fat diet can lower the chances of the cancer coming back by 24 percent.
The Wall Street Journal 1/31/2006