While dietary antioxidants have long been touted to help prevent cancer, a new study claims otherwise, revealing that these molecules cause the cancer cells to spread more quickly.

A team of scientists from the Children’s Research Institute at University of Texas Southwestern, or CRI, found that healthy people do benefit from antioxidants. However, the researchers advise cancer patients against infusing large doses of antioxidants on their diets, according to the study which appeared in the journal Nature.

In an experiment, the researchers transplanted melanoma cells from human patients to rats to observe metastasis, or the process by which cancer cells disseminate from their primary site to other parts of the body. Metastasis often leads to the death of most cancer patients.

CRI Director Dr Sean Morrison and his colleagues found that when antioxidants were administered to the mice, they manifested higher levels of cancer cells in their blood, and grew more tumours that were more widespread, compared to the group of mice that did not get antioxidants.

“We discovered that metastasising melanoma cells experience very high levels of oxidative stress, which leads to the death of most metastasizing cells. Administration of antioxidants to the mice allowed more of the metastasizing melanoma cells to survive, increasing metastatic disease burden,” says Morrison.

He explains that since antioxidants have been strongly touted as good for the body, there have been clinical trials done in which cancer patients were administered antioxidants. However, some of those trials had to be stopped because the patients getting the antioxidants were dying faster. Morrison says their data suggest that this is because cancer cells benefit more from antioxidants than normal cells do.

According to Morrison, cancer-free people may very well benefit from antioxidants that can help reduce damage from highly reactive oxidative molecules generated by normal metabolism. He says that while the study’s results have not yet been tested in people, it raises the possibility that cancer should be treated with pro-oxidants. Cancer patients should also not supplement their diet with large doses of antioxidants, he adds.

Antioxidants are man-made or natural substances that may prevent or delay some types of cell damage, the U.S. Department of Health & Human Services states in its Web site. Vegetables and fruits are said to be good sources of antioxidants, which include vitamins C and E, selenium and carotenoids. While antioxidant-rich foods are considered healthy, research has not shown that antioxidant supplements to be beneficial in preventing diseases.

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