Antioxidants May Lead to Cancer Spread, Study Says

Baskets of acai berries that will be sold to the food processing industry and to the growing export market, in Abaetetuba, near the mouth of the Amazon river. Paulo Santos/Reuters

Antioxidants such as blueberries and green tea have long been viewed as beneficial for health, and perhaps even to bear preventative implications for cancer. But a new study published this week in Nature might refute that belief: Researchers from the University of Texas Southwestern Center have found that antioxidants may in fact accelerate cancer's spreading and growth in mice.

"The idea that antioxidants are good for you has been so strong that there have been clinical trials done in which cancer patients were administered antioxidants," Dr. Sean Morrison, CRI Director and Mary McDermott Cook Chair in Pediatric Genetics at UT Southwestern Medical Center, said in a press release. "Some of those trials had to be stopped because the patients getting the antioxidants were dying faster. Our data suggest the reason for this: cancer cells benefit more from antioxidants than normal cells do."

Related: Why Elephants Don't Get Cancer—and What That Means for Humans

For the study, researchers tested the prevention of metastasis—the spreading of cancer cells—by transplanting human skin cancer cells, or melanoma, to mice. Some of the cells had been treated with N-acetylcysteine (NAC), an antioxidant sometimes used to treat patients with HIV/AIDS and in nutritional supplements, reports The Washington Post. Another group of mice was given nothing.

Researchers discovered that mice that had received antioxidants actually saw cancerous tumors spread more quickly throughout their bodies, and the tumors were also larger as compared to those in mice that hadn't been treated with anything.

This isn't the first study to show that some cancer patients had tumors that actually increased in size when being treated with antioxidants, but this research is alarming given that the metastasis seen in mice is indicative of how these same cells would metastasize in humans.

Related: Omega-3 Supplements Are a Waste of Money

The study's authors posit that cancer be treated with pro-oxidants. "We discovered that metastasizing melanoma cells experience very high levels of oxidative stress, which leads to the death of most metastasizing cells," said Dr. Morrison. "Administration of antioxidants to the mice allowed more of the metastasizing melanoma cells to survive, increasing metastatic disease burden."