Throw Away Those Vitamins They May Be Harmful to Your Health
Abstract & Commentary
By Ralph R. Hall, MD, FACP, FACSM, Emeritus Professor of Medicine, University of Missouri-Kansas City, School of Medicine. Dr. Hall reports no financial relationship to this field of study.
Synopsis: Vitamin C supplementation prevents increases in endurance capacity and maximum oxygen uptake, because it prevents some cellular adaptations to exercise.
Source: Gomez-Cabera MA, et al. Oral administration of vitamin C decreases muscle mitochondrial biogenesis and hampers training-induced adaptations in endurance performance. Am J Clin Nutr 2008;87:142-149.
Acute physical exercise induces the generation of reactive oxygen species (ROS) in muscles and other organs. It has been generally accepted that increasing the concentration of antioxidants within the cell should provide protection against these oxidizing agents. However, recent results from some laboratories indicate that ROS can exert favorable effects in training adaptation and in other metabolic systems. These studies concluded that muscle oxidative capacity (i e., the mitochondrial content of muscle) was the major determinant of endurance capacity, whereas maximum oxygen uptake (VO2max) was only indirectly related to endurance capacity.1,2
The aim of the study by Gomez-Cabrera et al was to explore the effects of vitamin C administration on training-induced increases in VO2max, endurance capacity, and mitochondrial content in both animals and humans.
The human study was randomized and double-blind. Fourteen men (ages 27-36 years) trained for 8 weeks. Five of the men received supplementation with an oral dose of 1 g of vitamin C.
In the animal studies, 24 male rats were exercised under two different protocols for 3 and 6 weeks. Twelve of the rats were treated with comparable doses of vitamin C. Vitamin C levels were measured in both the human and animal studies to verify proper vitamin C intake.
Vitamin C significantly hampered endurance capacity (P = 0.014). The running time in the rats increased from 101 minutes in the un-supplemented rats to 284 minutes, but only from 101 minutes to 128 minutes in the supplemented rats after training. The VO2max increased 17% in the un-supplemented rats but only 4.7 % in supplemented rats. The greater VO2max in the un-supplemented rats was not statistically significant. (The authors reasoned that this was probably due to the small number of subjects.)
Muscle biopsies from the un-supplemented rats had significantly higher levels of markers of mitochondrial content and of the bodies' own antioxidants (superoxide dismutase and glutathione peroxidase) than the supplemented rats.
In the human studies, VO2max increased 22% in the un-supplemented group and only 10.8% in the supplemented group. Cytochrome C, a marker of mitochondrial content, increased significantly more in the un-supplemented men.
Commentary
In 1971, it was noted that vitamin E supplementation (400 IU/d) caused unfavorable effects in endurance performance. More recently, Ristow et al reported that a combination of 400 IU/d of vitamin E and 1 g of vitamin C/d prevented the increase in insulin sensitivity and expression of endogenous ROS defense (superoxide dismutase and glutathione peroxidase) in exercised human subjects.3
It is now recognized that ROS are important in modulating gene expression in a favorable manner. They serve to stimulate the body's own antioxidants as well as having favorable effects on mitochondrial development. Since exercise has been shown to prolong life and promote a number of beneficial effects, it is important that we do not unnecessarily use supplements that can prevent these benefits. It is better to get your antioxidants from healthy foods and to exercise to increase your body's own antioxidant production.
References
1. Gomez-Cabrera MC, et al. Decreasing xanthine oxidative-mediated stress prevents useful cellular adaptations to exercise in rats. J Physiol 2005;567:113-120.
2. Khassaf M, et al. Effect of vitamin C supplements on antioxidant defence and stress proteins in human lymphocytes and skeletal muscle. J Physiol 2003; 549:645-652.
3. Ristow M, et al. Antioxidants prevent health-promoting effects of physical exercise in humans. Proc Natl Acad Sci U S A 2009;106:8665-8670.
Vitamin C supplementation prevents increases in endurance capacity and maximum oxygen uptake, because it prevents some cellular adaptations to exercise.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content. TESTING
- Award-winning Medical Content
- Latest Advances & Development in Medicine
- Unbiased Content