We routinely hear reports about antioxidants protecting us from serious illnesses, such as cancer. Many women have taken this information to heart and regularly take antioxidant vitamins and supplements. However, there are conflicting reports as to whether antioxidants help-or hurt-during chemotherapy treatments for breast cancer.

What are antioxidants?

The cells in our bodies produce by-products (molecules) as they perform their normal functions. These molecules can interact with oxygen to create free radicals, or unstable atoms. When these free radicals affect our DNA or cell membranes, they interfere with cell functioning and may lead to the development of cancer. Environmental toxins, such as tobacco smoke, can also lead to the formation of free radicals, which may play a role in the development of cancer. Antioxidants protect us, preventing cell damage from free radicals.

The most common antioxidants are vitamins C and E, beta-carotene (a precursor to vitamin A), selenium, lutein and lycopene. Most fruits and vegetables are rich in antioxidants. Our body cannot produce antioxidants on its own, which is why we are encouraged to have diets based predominantly on plant-based foods. Medical experts observe lower cancer rates in people who eat lots of fresh fruits and vegetables. They suspect antioxidants are at work, but so far, there is inconclusive evidence.

Do antioxidants affect breast cancer treatment?

Recently, there has been a flurry of studies about the effect of antioxidants on chemotherapy treatment for breast cancer. The studies return conflicting results; so it's difficult for patients to make fact-based decisions about using antioxidant supplements.

In studies, researchers find that antioxidants may:

  • reduce the effectiveness of chemotherapy,
  • protect cancer cells as well as healthy cells, or
  • protect normal tissue from chemotherapy damage.

A recent review of current research on chemotherapy and antioxidants in breast cancer patients found data supporting the use of antioxidants during chemotherapy; however, most of these results were from the lab, not from human studies. They concluded that the effect (positive or negative) of chemo depends, at least in part, on which antioxidants, at what dose and with what type of chemotherapy.

The bottom line

At the American Association of Cancer Research's annual meeting in April 2009, a leading physician from the department of nutrition at the Harvard School of Public Health said the bottom line is that we should not draw conclusions based on the results of any single study. If you currently take antioxidant supplements and are facing chemotherapy for breast cancer, consult with a knowledgeable practitioner.