Antioxidants have long been touted for their health benefits, but it turns out they may have a dark side.

A new study has found that antioxidants actually promote cancer growth in mice, which falls in line with observations in other studies that cancer patients who were treated with antioxidants actually saw their tumors grow, according to a UPI report.

The study was spearheaded by Dr. Sean Morrison, CRI Director and Mary McDermott Cook Chair in Pediatric Genetics at the University of Texas Southwestern Medical Center, who released his findings in a press release.

Instead, cancer patients may benefit more from pro-oxidants, Morrison and his team found.

Researchers looked into how metastasis happens, which is when cancer goes from the primary tumor to other parts of the body. Typically, cancer cells don’t survive in the blood stream, but in testing on mice, treating them with antioxidants caused the cancer to spread more quickly and survive transit through the blood stream.

Pro-oxidants could be better in this case, as oxidative stress limits metastasis based on this work, which involved melanoma cells.

Antioxidants have been praised for their health benefits so much that they have been incorporated into treatments of cancer patients, but things haven’t gone as expected. Trials often had to be stopped because the patients were suddenly dying faster due to the antioxidant treatment regimen.

The findings were published in the journal Nature.

Here is an excerpt from the press release, which was published Oct. 14: