Large doses of antioxidants can actually encourage the growth and spread of skin cancer. Share on Pinterest In the 1990s, researchers began singing the praises of antioxidants as effective weapons against everything from heart disease to cancer to age-related chronic conditions. Now, some scientists are putting antioxidant supplements on the caution list for people who are battling cancer. A study published today by the University of Gothenburg in Sweden concludes an excess of antioxidants may speed up the spread of skin cancer. The researchers recommend that people with melanoma not ingest extra antioxidants outside of their normal diet. “It is not far-fetched to suggest that antioxidant supplementation could increase metastasis in a patient with this disease and we would therefore recommend avoiding these supplements,” Martin Bergö, Ph.D., a professor in the university’s department of molecular and clinical medicine and co-author of the study, told Healthline. However, Bergö — along with an American Cancer Society official — say antioxidants are probably fine in a regular diet, especially for people who don’t have cancer. Read More: Deadly Skin Cancer Rate Has Doubled »

What the Researchers Found In their study, Bergö and his team used genetically altered mice with melanoma. The mice developed tumors closely resembling those in humans. The researchers then fed some of the mice water containing an antioxidant called N-acetylcysteine. The antioxidant had no effect on the number and size of primary tumors, but it did enhance the migration and invasion of these tumors into other parts of the body. They said the mice that drank the antioxidant-treated water had twice the number of metastatic tumors in lymph nodes compared to the other mice. The researchers also exposed human melanoma cells in culture to N-acetylcysteine and another antioxidant and that produced similar results. The scientists theorize the antioxidants activate a protein that regulates cytoskeletal changes in migrating cells called RHOA, encouraging the spread of the skin cancer. Bergö noted this is important because the spread of melanoma is what makes it lethal. “Growth of the primary tumor on the skin is not dangerous and this tumor is often removed by surgery,” said Bergö. “So, identifying factors that can affect metastasis is crucial.” Cancer patients are more likely to supplement their diet with substances such as antioxidants than healthy people, making this an especially relevant discovery. Read More: Fewer Moles Can Still Mean High Skin Cancer Risk »