Antioxidants May Speed Up Cancer Growth

Many studies have shown that eating fruits and vegetables that are rich sources of antioxidants reduces cancer risk. However, other studies show that high-dose antioxidants pills may increase risk of cancer and speed the growth of existing cancers. Now Swedish researchers have found that vitamin E pills tripled the growth of human lung cancer cells in a test tube and doubled the death rate from lung cancer in mice (Science Translational Medicine, published online Jan. 29, 2014). The effects increased with larger doses. The authors stated that "the results are suggestive that it might be applicable to other types of cancer."

How Could Antioxidants Increase Cancer Risk? Antioxidants are supposed to protect the body from disease by preventing cell damage caused by oxidant molecules called free radicals. Oxidants damage DNA to cause cancer. Your body tries to protect you from oxidant damage. When DNA in your body is damaged, it releases a major tumor-suppressing protein called p53. Antioxidants such as vitamin E prevent the body from making p53.

Many studies in both humans and animals show that antioxidants can increase cancer growth in people and animals that already have cancer. When a person has cancer, antioxidants suppress the release of p53 by halting DNA damage done to cancer cells by free radicals. "By reducing the DNA damage in cancer cells, the antioxidant actually helps the cancer cells escape detection," said author Per Lindahl. The findings suggest that people carrying small undiagnosed tumors in their lungs could be harmed by taking antioxidants other than those occurring in a healthful diet that includes plenty of fruits and vegetables.

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