The use of antioxidant supplements during chemotherapy and radiation is a controversial topic, and clinical studies have reported conflicting evidence. The Journal of the National Cancer Institute recently published a review of randomized trial data, which suggested that cancer patients should avoid the routine use of antioxidant supplements because they may potentially decrease the efficacy of cancer therapy by protecting the tumor and reducing survival.

The researchers looked at clinical trials investigating the impact of antioxidants on radiation therapy and found evidence suggesting that antioxidant supplementation reduced overall survival. However, they also found evidence that a particular antioxidant called amifostine might protect healthy tissues from radiation damage without increasing the radiation-resistance of cancerous tissues. The researchers also looked at sixteen trials that focused on the effects of antioxidant supplements on the efficacy of chemotherapy. They found no evidence that antioxidant use adversely affected response to treatment. However, they also did not find compelling evidence that antioxidant supplementation provided any additional benefit in treatment response.

It's still not clear whether antioxidant supplements are safe or how they might affect cancer therapy, but further research on the topic is warranted, especially with the widespread availability of, and food advertising associated with, antioxidants.