Many people take vitamins as part of their daily fitness regimens, having heard that antioxidants aid physical recovery and amplify the impact of workouts. But in another example of science undercutting deeply held assumptions, several new experiments find that antioxidant supplements could actually reduce the benefits of training.
Antioxidants became popular dietary supplements largely because they were said to sop up free radicals, the highly reactive oxygen molecules that are generated during daily activities. Through its breakdown of oxygen, physical exertion results in the creation of large numbers of these molecules, which, in excess, can lead to cell death and tissue damage.
So it seems logical that reducing the number of free radicals produced by exercise would be desirable.
Enter antioxidants, which absorb and deactivate free radicals.
While the body creates its own antioxidants, until recently many researchers believed that we produce too few natural antioxidants to counteract the damage caused by free radicals created during exercise. Many people who exercise began downing large doses of antioxidants such as vitamins C and E, even though few experiments in humans had examined the precise physiological impacts of antioxidant supplements in people who work out.
For a study published in The Journal of Physiology, researchers with the Norwegian School of Sport Sciences in Oslo and other institutions gathered 54 healthy adult men and women, most of them recreational runners or cyclists, and conducted a series of tests. They included muscle biopsies, blood tests and treadmill runs, to establish the subjects’ baseline endurance capacity and the cellular health of their muscles.
Then they divided the volunteers into two groups. Those in one group took four pills a day, delivering a total dose of 1,000 milligrams of vitamin C and 235 milligrams of vitamin E. Members of the second group got identical placebo pills.
Finally, all of the participants were asked to complete a vigorous 11-week training program, consisting of increasingly intense interval sessions once or twice a week, together with two weekly sessions of moderately paced, one-hour runs. By the end, all of the volunteers were more fit than they had been at the start, with their maximum endurance capacity increasing by an average of about 8 percent.
But their bodies had responded quite differently to the training.
LESS IMPROVEMENT
The runners who had swallowed the placebo pills showed robust increases of biochemical markers that are known to goose the creation of mitochondria, the tiny structures within cells that generate energy, in cells in their bloodstream and muscles. More mitochondria, especially in muscle cells, mean more energy and, by and large, better health and fitness. The creation of new mitochondria is generally held to be one of the most important effects of exercise.
But the volunteers who had consumed the antioxidants had significantly lower levels of the markers related to mitochondrial creation. The researchers didn’t actually count the specific populations of mitochondria within their volunteers’ muscle cells, but presumably, over time, those taking the antioxidants would see a smaller increase in mitochondrial density than among those not taking them.
That finding echoes the results of another study of antioxidant supplementation and exercise, published last year in The Journal of Physiology, in which half of a group of older men took 250 milligrams daily of the supplement resveratrol, an antioxidant found in red wine, and the other half took a placebo.
After two months of exercising, the men taking the placebo showed significant and favorable changes in their blood pressure, cholesterol profiles and arteries, with fewer evident arterial plaques.
The men taking the resveratrol were not as fortunate. They had exercised as much as the other men, but their blood pressures, cholesterol levels and arteries had remained almost unchanged.
GOOD RADICALS?
Why and how antioxidant supplements blunt the effects of exercise is not altogether clear, said Goran Paulsen, a researcher at the Norwegian School of Sport Sciences, who led the vitamins C and E study. But he and other physiologists have begun to suspect that free radicals play a different role during and after exercise than previously thought.
In this theory, free radicals are not villainous but instead serve as messengers, nudging genes and other bodily systems into starting the various biochemical reactions that result in stronger muscles and better metabolic health. Without free radicals, those reactions don’t begin.
And large doses of antioxidant supplements absorb most of the free radicals produced by exercise.
Of course, that theory is still unsubstantiated and requires long-term testing in people, Paulsen said. It is possible, he said, that smaller doses of antioxidants or different formulations might be useful for athletes.
Also, natural antioxidants from food sources like blueberries and red wine are unlikely to be problematic, he said.
“It’s probably only concentrated extracts that are potentially dangerous,” he said.
Volunteers who took the concentrated extracts of vitamins C and E did increase their endurance to the same extent as those taking a placebo. On the other hand, the supplements did not improve performance in comparison with a placebo, so why bother with them? Paulsen asked.
“Personally, I would avoid high dosages” of antioxidants while training, he said. The science on the topic is not complete, but the intimation of the recent studies is that by taking the supplements, “you risk losing some of the benefits of exercise.”
ActiveStyle, Pages 23 on 03/10/2014