A new paper from Sahlgrenska Academy in Gothenburg shows that
Antioxidants can increase melanoma metastasis in mice, K Le Gal et al, Science Translational Medicine, 07 Oct 2015:
Vol. 7, Issue 308, DOI: 10.1126/scitranslmed.aad3740
First antioxidants were good for you, then they were of doubtful benefit and now it seems they are positively bad. Many foods containing antioxidants have been touted for their health benefits and have included chocolate, fresh fruits and vegetables, nuts, whole grains, maize, legumes and eggs. Red wine was on the list but the benefits of Resveratrol have already come under a cloud for alleged data tampering.
Of course, perceived antioxidant benefits have not much influenced my own consumption of dark chocolate and red wine. But what the study finds is that “the overall conclusion from the various studies is that antioxidants protect healthy cells from free radicals that can turn them into malignancies but may also protect a tumor once it has developed”.
So antioxidants can help prevent a cancer developing, but once the cancer is there antioxidants can speed up the progression of the cancer. Dark chocolate and red wine therefore remain on the “good foods list” for those who do not have any cancerous cells.
Fresh research at Sahlgrenska Academy has found that antioxidants can double the rate of melanoma metastasis in mice. The results reinforce previous findings that antioxidants hasten the progression of lung cancer. According to Professor Martin Bergö, people with cancer or an elevated risk of developing the disease should avoid nutritional supplements that contain antioxidants.
Researchers at Sahlgrenska Academy, University of Gothenburg, demonstrated in January 2014 that antioxidants hastened and aggravated the progression of lung cancer. Mice that were given antioxidants developed additional and more aggressive tumors. Experiments on human lung cancer cells confirmed the results.
Given well-established evidence that free radicals can cause cancer, the research community had simply assumed that antioxidants, which destroy them, provide protection against the disease. Found in many nutritional supplements, antioxidants are widely marketed as a means of preventing cancer. Because the lung cancer studies called the collective wisdom into question, they attracted a great deal of attention.
The follow-up studies at Sahlgrenska Academy have now found that antioxidants double the rate of metastasis in malignant melanoma, the most perilous type of skin cancer. Science Translational Medicine published the findings on October 7.
“As opposed to the lung cancer studies, the primary melanoma tumor was not affected,” Professor Bergö says. “But the antioxidant boosted the ability of the tumor cells to metastasize, an even more serious problem because metastasis is the cause of death in the case of melanoma. The primary tumor is not dangerous per se and is usually removed.”
Experiments on cell cultures from patients with malignant melanoma confirmed the new results. “We have demonstrated that antioxidants promote the progression of cancer in at least two different ways,” Professor Bergö says.
The overall conclusion from the various studies is that antioxidants protect healthy cells from free radicals that can turn them into malignancies but may also protect a tumor once it has developed.
Taking nutritional supplements containing antioxidants may unintentionally hasten the progression of a small tumor or premalignant lesion, neither of which is possible to detect.
“Previous research at Sahlgrenska Academy has indicated that cancer patients are particularly prone to take supplements containing antioxidants,” Dr. Bergö says. “Our current research combined with information from large clinical trials with antioxidants suggests that people who have been recently diagnosed with cancer should avoid such supplements.”