Should Athletes take Vitamin C?

Remember eating oranges during halftime of a soccer game? Well, Vitamin C (ascorbic acid) does have its benefits. It helps to repair and regenerate tissues, protect against heart disease, aid in the absorption of iron  and decrease total and LDL ("bad") cholesterol and triglycerides. Research indicates that Vitamin C may help protect against a variety of cancers by combating free radicals, and help neutralize the effects of nitrites. 

Vitamin C is also an essential nutrient. Since your body doesn't produce or store Vitamin C, it's important to include Vitamin C in your diet. If you are naturally deficient or elderly, there can be a benefit for supplementation. For most people, a large orange, 1 cup (about 165 grams) of sliced strawberries, chopped red pepper or broccoli provide enough vitamin C for the day. Any extra Vitamin C will simply be flushed out of your body in your urine. 

Still, is it possible to have too much Vitamin C? For adults, the recommended dietary reference intake for Vitamin C is 65 to 90 mg a day, and the upper limit is 2,000 mg a day. Although too much dietary Vitamin C is unlikely to be harmful, mega-doses of Vitamin C supplements may cause: 

  • Diarrhea
  • Nausea/Vomiting
  • Heartburn
  • Abdominal bloating and cramps
  • Headaches

But should supplementing with Vitamin C be a part of an endurance athlete’s training protocol? For its benefits, there may be some downside to taking Vitamin C.

In 2008, researchers at the University of Valencia published the results of a study in which a daily dose of 1 gram of Vitamin C undermined the effect of 8 weeks of running training. The study's results showed Vitamin C hampered adaptations to exercise and in turn decreasing training effectiveness. 

Further, in 2010 German nutritionists asserted that high doses of Vitamin C and E, both antioxidants, can inhibit the body’s adjustment to physical training.  But, at the same time, according to a Danish study, published in Medicine & Science in Sports & Exercise, the news is not so bad. The Danes did not discover a single negative effect of Vitamin C or E. But they didn't discover any positive ones either.

According to the researchers, "considering that the health conscious part of the population generally consumes a balanced diet, rich in fruits and vegetables, our data suggest that this population will not experience any effect - positive or negative - from moderate daily vitamin supplements on training adaptation in response to strenuous endurance training…In conclusion, healthy people who just exercise regularly should be more critical towards antioxidant supplements."

Remember, for most people a healthy diet provides an adequate amount of Vitamin C and the jury appears to still be out as to whether antioxidants inhibit cellular adaptations to exercise. Endurance athletes should consider these points before supplementation.