Vitamins are obviously an essential component to your overall health. They help regulate and perform body functions, but certain types of vitamins taken before exercise may actually decrease the fitness benefits. Dr. Michael Ristow, nutritionist at the University of Jena in Germany, conducted a research study in 2009 that suggests people exercising to improve metabolism and prevent diabetes may want to avoid vitamins C and E.
Exercise requires a glucose and insulin response for energy production, and vitamins C and E have been tested for their effect on the body's glucose metabolism. Both vitamin C and E are antioxidants that support healthy bone and skeletal development and immunity. However, Dr. C. Ronald Kahn from the Joslin Diabetes Center in Boston says that vitamins have a significant impact on glucose metabolism by blocking the effects of insulin on the metabolic response.
Performing short-term physical exercise increases the amount of free radicals with the body and skeletal muscles. As a result, your body reacts by using antioxidant supplements such as vitamins C and E to reduce free radical production. However, the additional antioxidants within the body block exercise-induced benefits to glucose metabolism. Ristow found that by blocking the improvement to insulin sensitivity there was no improvement to your body's defense mechanism against free radicals and oxidative damage.
Ristow suggests that the negative effects of taking vitamins before exercise don't include the vitamins found in whole foods such as fruits and vegetables. The additional substances in the whole foods must offset the negative effects from the vitamins. In order to prevent any issues, avoid consuming vitamin supplements and vitamin-rich fruits and veggies immediately before your workout.
The most important consideration for taking vitamins before exercise is to consult your doctor and registered dietitian. They can examine your individual nutrition plan to ensure you are consuming sufficient amounts of vitamins along with examining your exercise requirements to determine if you have an increased risk for exercise-related health concerns.