Antioxidant vitamins are enormously popular with people who exercise. The supplements are thought to alleviate muscle damage and amplify the effects of exercise. But recent studies have raised questions about whether antioxidants might be counterproductive for runners and other endurance athletes.
And now a cautionary new experiment adds to those doubts by finding that antioxidants may also reduce the benefits of weight training.
It is easy to see why people might think that antioxidants like vitamins C and E could be helpful to anyone who works out regularly. Both aerobic exercise and strength training lead to the production of free radicals, molecules that in concentrated amounts can cause tissue damage. Antioxidants sop up and neutralize free radicals. So, the thinking goes, taking an antioxidant should lessen some of the damage and soreness after exercise and allow people to train harder.
But recent experiments with endurance athletes have found that consuming large doses of vitamins C and E actually results in a slightly smaller training response. The athletes taking these vitamins had lower levels of certain enzymes that spur an increase in the mitochondria in muscle cells.
Mitochondria help create cellular energy, and having more of them allows people to exercise longer and harder. By blunting the creation of mitochondria, the vitamins had lessened the expected increase in fitness.
But those studies looked only at endurance sports such as running and cycling, not weight training, which involves different biochemical processes within muscles.
So for the new study, which was published online Oct. 30 by The Journal of Physiology, scientists at the Norwegian School of Sports Sciences in Oslo and other institutions, some of which already had done studies on aerobic exercise and antioxidants, set out to repeat those experiments in a weight room.
They began by recruiting 32 men and women who had at least some experience with weight training.
They measured the volunteers' muscular size and strength.
Then they randomly divided them into two groups. Half were asked to start taking two antioxidant vitamin pills each day, one before and one after exercising. The total daily dosage amounted to 1,000 milligrams of vitamin C and 235 milligrams of vitamin E, which "is high but not higher than athletes commonly use," said Dr. Goran Paulsen, a professor at the Norwegian School of Sports Sciences, who led the study.
The other group did not take any supplements.
All of the volunteers then began the same resistance-training regimen, consisting of four fairly rigorous sessions each week. As the exercises grew easy, weights were increased, with the aim of pumping up the size and strength of the volunteers' muscles.
The program lasted 10 weeks. Midway through that time, the researchers took small samples of muscle tissue from each volunteer to determine what, precisely, was going on deep within each volunteer's cells.
Then the men and women finished the program, at the end of which the researchers again measured their strength and muscle size.
In general, people's muscles had increased in size to the same extent, proportionally. The group that had taken the vitamins now had larger muscles. So did the group that had not.
But there were subtle but significant differences in their strength gains. Overall, the volunteers who had taken the antioxidants had not added as much strength as the control group. Their muscles were punier, although they had grown in size.
The differences continued beneath the skin, where, as the muscle biopsies showed, the volunteers taking the vitamins had reduced levels of substances known to initiate protein synthesis. Protein synthesis is necessary to repair and strengthen muscles after weight training.
So the volunteers taking the vitamins were getting less overall response from their muscles, even though they were following the same exercise program.
Exactly how antioxidant pills change muscles' reactions to weight training is still unknown. But Paulsen and his colleagues think that, by reducing the number of free radicals after exercise, the vitamins short-circuit vital physiological processes.
In this scenario, free radicals are not harmful molecules but essential messengers that inform cells to start pumping out proteins and other substances needed to improve strength and fitness. Without enough free radicals, you get less overall response to exercise.
Paulsen believes the same process occurs after endurance exercise, although the specific biochemical signals and pathways are different.
The upshot is that whether you lift weights or jog, Paulsen would advise "against the use of high dosages of concentrated antioxidant supplements."
Of course, his advice does not apply to anyone with an actual deficiency of one of the antioxidants, he said, although that condition is rare.
He also doesn't suggest that we avoid orange juice or other natural sources of vitamins C and E while training. "But large volumes," he said, "would be unnecessary."
ActiveStyle on 12/15/2014