Foods rich in antioxidants are touted as must-eat superfoods that help the body defend itself from evil free radicals.

Free radicals are uncharged electrons that can circulate in the body, harming our cells by pulling electrons off molecules to stabilize themselves. In turn, this degrades cells a bit at a time. Antioxidants, contained in many fruits, veggies and nuts, as well as skin-on potatoes, neutralize the free radicals to help our cells stay healthy.

But a research team from Texas has learned something unsettling. According to their study published in Nature, it looks like cancer cells benefit from antioxidants’ positive effects, too.

In the study, mice that had a human form of melanoma were divided into two groups. One group received antioxidant-rich injections, while the other did not. The mice that received the antioxidant injections had significantly greater levels of cancer cells in their blood compared to mice in the other group. This would make sense if the antioxidants were helping to protect the cancerous cells by neutralizing free radicals.

For cancer cells, it can be difficult to spread to other organs. Scientists say free radicals kill some cancer cells as they try to metastasize. But in this study, the researchers found that by killing the free radicals, the antioxidants could be helping cancer cells spread.

Tumor metastasis is bad news for the patient. The tumor cells often land in other organs. When this happens, the disease and the treatment both become more difficult to bear.

More research is required to evaluate the role of antioxidants in the spread of cancer through the body. However, experts say people should not be afraid to eat fruits and vegetables, which contain essential nutrients. But the view of antioxidants as miraculous cancer-fighters may need rethinking.