Doctors Warn Cancer Patients to Avoid Vitamins

High Doses of Antioxidants Cautioned Against During Chemo, Radiation

Jun 8, 2009

Although there's no conclusive evidence either way, some cancer experts recommend antioxidants while others insist chemo patients avoid vitamins that could interfere.

Antioxidants are widely touted to heal cells and fight cancer, so it's no wonder that many women being treated for breast cancer continue – or begin – to use antioxidant supplements during chemo or radiation treatment. But many cancer doctors violently oppose the use of vitamins, since research suggests that antioxidants may interfere with radiation and chemotherapy.

Why Take Antioxidants During Cancer Treatment?

Antioxidants are natural chemicals found in fruits, raw vegetables, and other plant sources. These chemicals protect cells against damage – including normal age-related damage, sun damage, or radiation that can alter a cell's growth and cause cancer. Said to be vital in anti-aging and immune-boosting therapies, antioxidants have become big business in the health food industry.

Antioxidants became a key word in marketing vitamins, supplements and foods in the last decade as "cancer fighters" or "cancer preventatives" – but that doesn't necessarily make them good for those who already have cancer.

"Studies suggest that just like healthy cells, cancer cells thrive in the presence of high doses of antioxidants," reports Tara Parker-Pope in the New York Times' Health section (8 June 2009). Cancer experts suggest that antioxidant supplements might directly interfere with chemotherapy and radiation treatments by protecting cancer cells just as they would protect normal, healthy cells from radiation damage.

New Study: Cancer Patients Continue Taking Vitamins

New research conducted at the Columbia University Mailman School of Public Health reveals that of 764 women treated for breast cancer, 61% were taking antioxidant vitamins or supplements, although their doctors weren't always aware of it. The study asked specifically about the popular antioxidants vitamin C, vitamin E, selenium and beta carotene, while ignoring less common antioxidant supplements.

Of the cancer patients who were taking antioxidants during chemo or radiation treatment, 69% were using higher than normal doses, some of which may have been prescribed by natural practitioners to protect against side effects or boost overall health and immunity during cancer treatments.

The study concludes by recommending that further research be conducted: "Given the common use of antioxidant supplements during breast cancer treatment, often at high doses and in conjunction with other complementary therapies, future research should address the effects of antioxidant supplementation on breast cancer outcomes."

How Many Antioxidants Are Too Many for Cancer Treatments?

The bottom line is that even the doctors who urge patients to avoid all vitamins and supplements during treatment don't know what to say when faced with the hard questions.

"People ask me, 'What should I eat?' And we just don't know," says Gabriella D'Andrea in an interview with U.S. News reporter Katherine Hobson. D'Andrea is an oncologist at Memorial Sloan-Kettering Cancer Center in New York.

Fruits and vegetables contain antioxidants, but they're also part of a balanced diet that is key to keeping the immune system and the rest of the body strong during invasive treatments like radiation and chemo. It seems there is no simple answer.

It remains possible that vitamins and antioxidants don't interfere with chemo or other cancer treatments at all – studies just haven't been done to enable doctors to be sure one way or the other. But until it's certain, it's always a good idea to advise your doctor of any vitamin supplements or natural treatments being used concurrently with medication or treatment.

Sources

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