Should You Take Vitamins C and E Supplements?

Pain pills, vitamins and supplements are found in nearly every runner’s home, but in recent years one of the hottest areas of exercise research has questioned their value. In particular, some studies have concluded that the pills might interfere with biological processes that help us get healthier, fitter and faster. Much of the research has been conducted on animals, and the findings are anything but conclusive.

A new human study published in the Journal of Physiology suggests that runners should think twice about taking two popular supplements, vitamins C and E. As the study authors put it in their conclusion, “Vitamin C and vitamin E hampered cellular adaptations in the exercised muscle, and we advocate caution when considering antioxidant supplementation combined with endurance exercise.”

The experiment lasted 11 weeks, with the 54 subjects following a progressive training plan that reached four 30- to 60-minute workouts (mostly running) a week. Except for the 60-minute runs, the others were all classified as high-intensity, and included tough interval sessions. Subjects took 1000 milligrams of vitamin C and 235 milligrams of vitamin E, or placebo pills, daily. Researchers did before-and-after biopsies of the subjects’ quadriceps muscles.

The results are a bit confusing. All subjects improved by similar amounts in both VO2 max and in a standardised shuttle run to exhaustion. In other words, the supplements did not diminish their endurance performance. Rather, say the researchers, the supplements interfered “with exercise-induced cell-signalling in cell muscle fibres.”

They add: “It is intriguing to note that the four participants with the largest improvements in running performance were all in the placebo group.” Also: “We observed improved fat oxidation and reduced heart rates at submaximal workloads in the placebo group.” Finally, the muscle tissue of the supplemented runners showed signs of increased oxidative stress.

“Thus, supplementation with high dosages of vitamin C and E appears to diminish some of the endurance training-induced adaptations in human skeletal muscle,” the authors say. “We suggest that high dosages of isolated antioxidants should be used with caution when simultaneously engaged in endurance training.”

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