Source: U.S. Department of Health & Human Services, National Institutes of Health, Office of Dietary Supplements (2017).
Antioxidants (vitamin C, vitamin E, and coenzyme Q10)
|DOES IT WORK?||No. The free radicals that form when you exercise seem to help muscle fibers grow and produce more energy. Antioxidant supplements might actually reduce some of the benefits of exercise, including muscle growth and power output. Also, they have little effect on aerobic fitness and performance in endurance activities like distance running.|
|IS IT SAFE?||Everyone needs adequate amounts of vitamin C and vitamin E for good health. Getting too much of these nutrients can be harmful, but the amounts of vitamin C (about 1,000 milligrams) and vitamin E (about 500 IU) typically used in studies of performance supplements are below safe upper limits. The side effects from coenzyme Q10 can include tiredness, insomnia, headaches, and some gastrointestinal (GI) discomfort, but these effects tend to be mild.|
|BOTTOM LINE||There’s little scientific evidence to support taking supplements containing vitamins C and E or coenzyme Q10 to improve performance if you’re getting adequate amounts of these nutrients from a nutritious diet.|
|REMARK||Many performance supplements in the marketplace contain more than one ingredient, and ingredients can work differently when they’re combined. Because most ingredient combinations have not been studied, it is not known how effective or safe they are in improving performance.|