Antioxidants, like vitamin C and E are known to have anti-cancer benefits, but a new research in mice, the results of which were reported recently in the journal Science Translational Medicine seem to suggest that certain antioxidants can actually increase the risk of metastatic melanoma. Since, it helps in the spread of skin cancer in mice; researchers are worried about its safety in humans.
Martin Bergo, a professor at the University of Gothenburg in Sweden and a senior author of the study said to relieve mucus production in patients with chronic obstructive pulmonary disease (COPD), the antioxidant, N-acetylcysteine is often prescribed. Many people also use it as a dietary supplement to help reduce exercise-related muscle damage, burn fat and prevent fatigue. So, the researchers were shocked when they found that water laced with N-acetylcysteine seemed to accelerate the spread of melanoma. In their study, it was observed that the antioxidant has no effect on the size and the number of tumors, but it did enhance the migration and invasion of these tumors to other parts of the body. Their findings say that N-acetylcysteine was linked to a doubling of the number of lymph-node tumors in mice who drank the laced water, compared to untreated animals.
In some previous research the same research team has reported that some particular antioxidants enhanced lung tumor growth in mice.
The U.S. National Institutes of Health (NIH) says antioxidants are believed to protect healthy cells from damage caused by unstable molecules called “free radicals.” But, this study has shown that antioxidants like N-acetylcysteine protect cancer cells from free radicals that might otherwise slow their growth. There have been other studies which has linked high doses of beta-carotene to increased risk of lung cancer in smokers. NIH has say that high doses of vitamin E can heighten the risk of prostate cancer.
Bergo said if people who are at an increased risk of cancer take nutritional supplements containing antioxidants, it might do them more harm than good. The reason why Bergo's team decided to focus on N-acetylcysteine is because it is a potent antioxidant which quickly dissolves quickly in water making it easier to feed to lab mice.
To further their study, the research team performed follow-up lab tests on human melanoma cells, using N-acetylcysteine and vitamin E. The results were similar – both antioxidants increased the cancer cells' ability to migrate and invade other cells. It is understood that antioxidants’ protective benefits could provide the boost to skin cancer. The researchers also found that a protein that regulates cellular processes was activated in the cells and it was likely involved in the spread of cancer.
Bergo said that for a patient with newly diagnosed lung cancer or melanomaantioxidants could enhance the progression of the disease. There is no conclusive evidence that support antioxidant supplementation to help cancer patients and hence, it is more sensible to avoid it altogether as it can worsen the disease.
Dr. Len Lichtenfeld, deputy chief medical officer for the American Cancer Society, said that the study results are interesting, but it is not possible to take this information and directly translate it into recommendations for patients. He argued that the results of animal studies don’t necessarily translate into what happens for humans. Clinical trials in people are needed before we can conclude that antioxidants impact the course of cancer treatment.
Lichtenfeld did add that cancer patients should make sure their treatment team knows about all supplements, alternative medications and vitamins they take, so that they get the best advice possible for their particular situation.