Are antioxidants always good for you? Actually, maybe not
The world of nutrition and fitness is awash in buzzwords — but “antioxidant” may be the buzziest. Why are berries, dark chocolate, and leafy greens so good for you? Antioxidants. Why should you try this cleanse? Antioxidants. Why is this supplement superior? Well, it contains antioxidants, of course.
But what exactly are antioxidants and how do they impact your body? We delved into the science, and the answers to those questions may surprise you.
Can Antioxidants Ever Hurt Your Health?
If you have an excess supply of a single type of antioxidants — say, from a super-restrictive and quirky diet, or from a megadose antioxidant supplement — they can actually turn into pro-oxidants, meaning they promote the exact kind of damage antioxidants typically prevent, research shows.
That’s because free radicals aren’t always bad for you. In fact, they support some healthy and important changes within your body, says Mankowski. For instance, to help your muscles grow bigger and stronger, your body builds and repairs the tiny tears strength training creates in your tissues. Free radicals — normally thought of as bad guys — support these muscle changes.
“We need to micro-damage the muscle and involve other biochemical reactions, including formation of free radicals, in order to let the muscle recover,” Mankowski says.
In this case, antioxidants and their free-radical fighting powers can be a problem. Mankowski says some research on antioxidants, specifically types found in vitamins E and C, have been found to “blunt” the beneficial breakdown processes that result from exercise. He’s quick to add, however, that the research on antioxidants and exercise are mixed. In some cases, antioxidants may be helpful, but more research needs to be done to understand when and how.
During the 1980s and early 90s, one of the things researchers were excited about antioxidants and their ability to fight cancer. “There was a lot of interest in [the antioxidant] beta carotene and its anti-cancer effects,” says IHPI member Gilbert Omenn, M.D., Ph.D., a professor of human genetics and molecular medicine at the University of Michigan.
Dr. Omenn says that, back then, many preliminary studies had shown beta carotene — the red-orange pigment that gives carrots and sweet potatoes their vibrant color — could stop the growth of cancer cells, and there was a widespread belief that taking beta carotene as a supplement might benefit heavy smokers at risk for lung cancer.
So he and others launched a large-scale study in which heavy smokers took a daily supplement containing 30 milligrams of beta carotene, about the amount you would find in 10 ounces of cooked sweet potato. At the same time, a similar beta carotene study was underway in Finland.
“I was able to see the results of the Finland trial confidentially, before they were made public, and they were shocking,” Dr. Omenn says. Rather than preventing cancer, smokers in the Finnish study who took beta carotene were developing lung cancer in greater numbers than those taking a placebo.
“Our findings turned out to be the same, but were even more dramatic,” Dr. Omenn says. In his study—which he and his collaborators terminated early—a smoker’s risk for lung cancer jumped 20 percent if he took the beta carotene supplement, rather than a placebo. “It was maybe the most potent carcinogenic effect ever discovered,” he says.
What is happening? “Our findings triggered new laboratory studies,” he says. Turns out, when beta carotene is oxidized in the body, its breakdown products fire up well-established cancer pathways. More recent research has also linked antioxidant supplements with a greater risk of death, potentially due to that increased cancer risk and DNA or cell damage.