Two studies came out in the beginning of October 2015 suggesting that a certain antioxidant might cause skin cancer cells to metastasize faster than they normally would.

Many of you probably saw the absolutely terrifying headlines screaming that antioxidants made cancer cells spread faster. As usual, there is a grain of truth behind the headlines, but the real story isn’t quite as frightening and doesn’t mean that you should avoid all foods that contain antioxidants.

 

If you’d like to read the abstracts of the studies, they are:

• “Oxidative stress inhibits distant metastasis by human melanoma cells,” published online in Nature on Oct. 14, 2015
• “Antioxidants can increase melanoma metastasis in mice,” published in the Oct. 7, 2015 issue of Science Translational Medicine

Antioxidants are natural or man-made substances that may prevent or slow down some types of cell damage. Antioxidants are found in many foods, especially fruits and vegetables. Antioxidants are also available as dietary supplements that are taken as pills or powders. Some common antioxidants are:

• beta-carotene
• lycopene
• vitamin A
• vitamin C
• vitamin E

Antioxidants may help protect cells from substances called free radicals. Free radicals are produced when you’re exposed to some pollution such as tobacco smoke. Your body also produces free radicals when it breaks down food. Free radicals can damage cells and may contribute to certain diseases, including cancer. Research suggests that many women being treated for breast cancer are taking at least one antioxidant supplement, often at levels much higher than recommended in a healthy diet.

In the study published in Nature, the researchers transplanted skin cancer (melanoma) cells from people into mice. The researchers then split the mice into two groups.

One group of mice was given the antioxidant N-acetylcysteine (NAC). The other group got no antioxidants. The researchers found that the human skin cancer cells spread faster in the mice that got NAC compared to the mice that didn’t get NAC.

In the study in Science Translational Medicine, the researchers fed NAC to one group of mice that were genetically engineered to be susceptible to melanoma. They didn’t feed NAC to a second group of mice with the same genetic predisposition to melanoma. The amount of NAC the mice ate was similar to what people might consume if they took NAC supplements. The mice that were fed NAC didn’t develop more skin tumors than the mice that didn’t eat NAC, but they did have more tumors in their lymph nodes, suggesting that the NAC caused the cancer to spread faster. The researchers also added NAC or a form of vitamin E to melanoma cells in petri dish. The antioxidants improved the cancer’s cells ability to grow.

On the surface, these two studies sound really scary. But as I’ve told my patients, it’s important to know several things:

• These studies were done in mice and petri dishes, not people.
• NAC is a man-made supplement. It’s not found in any food. NAC is used as a medicine to reduce the amount of mucus produced by people with chronic obstructive pulmonary disease. It’s also used as a supplement by some people, such as body builders and weight lifters, who believe it can reduce exercise-related muscle damage, burn fat, and prevent fatigue.
• The amount of NAC the mice were given in the Science Translational Medicine study was similar to what people might consume if they were taking supplements, but it’s MUCH MORE than the level of any antioxidant you get from eating food. And, as I said above, you can’t get NAC from any food.

So the bottom line is that NAC, which you can only get if you take it as a supplement, seems to cause human skin cancer cells to grow and spread faster in mice.

Based on these two studies, I’m telling my patients two things:

• Don’t take antioxidant supplements. Supplements ARE NOT regulated by the U.S. Food and Drug Administration, so there is no guarantee that what’s on the label is exactly what’s in the pill or powder. And just because a product says “all natural” or “pure” doesn’t mean it comes from nature. Taking a supplement gives your body much higher levels of antioxidants than you could ever get from eating food.
• The best way to get the nutrients you need is by eating real food. By real food, I mean food that has only one or two ingredients and is minimally processed. Eat a diet that includes all the colors of the rainbow, including fruits, vegetables, nuts, seeds, grains, and protein. (If you’re getting your protein from animal food products, try to eat the highest quality you can afford.)

Have you asked your doctor about antioxidants? What did she or he say?