Study cautions against high dosages of vitamin C and E, especially for athletes

A study published today has raised concerns about the effects of vitamin C and E supplements on people involved in endurance training.

The research, published in the Journal of Physiology, found the vitamin pills could blunt the metabolic response of muscles to fitness training. Dr Gøran Paulsen, who led the study at the Norwegian School of Sport Sciences, said the study had identified a significant trend but further research was needed.

“Our results show vitamin C and E supplements blunted the endurance training-induced increase of mitochondrial proteins, which are needed to improve muscular endurance.”

In the 11-week trial, 54 young, healthy men and women were randomly allocated to receive either 1000mg vitamin C and 235mg vitamin E – the same amount found in shop supplements – or a placebo. They completed an endurance training programme which mostly involved running. Fitness tests, blood samples and muscle biopsies were taken before and after the intervention.

The supplements did not affect oxygen uptake or the results of a 20m shuttle test but they did show markers for the production of new muscle mitochondria – the power supply for cells – increased only in the group without supplements.