Some Vitamins May Undo the Benefits of Exercise in Diabetics

Just when you thought you’d got it right – plenty of exercise, eating right, and taking anti-oxidant supplements like vitamins C and E – along comes a report showing that the good things can cancel each other out. That’s the finding in a study reported in the Proceedings of the National Academy of Sciences.

Thirty-nine young men were allocated to two groups: one group took 1,000 mg daily vitamin C and 400 IU daily vitamin E, while the other group didn’t; both groups exercised intensely for 4 weeks. Before and after the 4-week study period two measures of insulin sensitivity were employed, and the blood levels determined of reactive oxygen species (ROS, or free radicals that are ‘mopped up’ by antioxidants).

Exercise normally increases levels of ROS, because of increased metabolism and the use of oxygen. In the study, the men who took the antioxidant supplements showed no changes in their ROS, while those who didn’t had increased ROS levels and oxidative stress. Importantly, insulin sensitivity and glucose metabolism only improved in the group not taking the antioxidants.

The researchers conclude that the positive effect of exercise on metabolism (oxidative stress that improves insulin resistance) is undone by antioxidant supplements. This could be especially important for type 2 diabetics.

This finding may be at first alarming to those who are aware of the harm done by free radicals blood vessels and other organs in the body. The point is that the boost in ROS induced by exercise is a good thing, with benefits on insulin sensitivity and carbohydrate metabolism. Like so many things in nature, a little of something can be good, while a lot can be bad . . .