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High doses vitamin C and E buffer cardio effect on fat rolls

You work up a good sweat running a couple of times a week, you watch what you eat - but those cuddly rolls of fat just won't shift. Sound familiar? German nutritionists may have discovered why this happens. According to their article, soon to be published in the prestigious PNAS, high doses of vitamin C [structure shown below] and E sabotage the healthy effect of training on insulin sensitivity.

Vitamin C
Obese people are more likely to develop diabetes because their fat makes the cells in their body insensitive to insulin. In healthy people, fitness gurus claim, a mild degree of insulin-insensitivity is what leads to those fat rolls around the midriff area. [Love handles: your plastic surgeon pays for his kids' horse riding from these.] Physical exercise makes the receptors in the muscle cells more sensitive.

A number of studies have shown that free radicals play a key role in the mechanism of insulin resistance. Humans and animals that continuously have high amounts of free radicals in their system become resistant to insulin. But these same free radicals are released in high quantities when you do intensive exercise. That's why the German researchers wanted to see whether it was possible to reinforce the positive effects of physical exercise by giving test subjects a daily dose of a thousand milligrams of vitamin C and four hundred units of vitamin E.

The researchers got forty people to exercise for four weeks. Half of the group had never done any sports; the other half did an average of one hour training daily. For the experiment all test subjects went to the gym five days a week, where they did forty minutes of circuit training and twenty minutes of biking. Half took vitamins; the other half got a placebo.

The figures below show how quickly the glucose disappeared from the subjects' blood. The higher the value, the greater the increase in insulin sensitivity. The white bars represent the starting situation; the coloured bars the situation after four weeks. Taking vitamins blocked the insulin-sensitivity improving effect of exercise.

High doses vitamin C and E buffer cardio effect on fat rolls
High doses vitamin C and E buffer cardio effect on fat rolls

Physical exercise increases the production of signal molecules like PGC-1-alfa and PGC-1-beta in the muscle cells. It also increases the manufacture of the 'fat sensor' or transcription factor PPAR-gamma. In both the trained and untrained subjects the vitamin supplement cancelled this effect. More PPAE-gamma means more fat burning. More PGC-1 alfa means more mitochondria.

High doses vitamin C and E buffer cardio effect on fat rolls

Physical exercise generates free radicals in the muscles. Muscle cells defend themselves against this by making more endogenous antioxidants such as superoxide-dismutase-1 and 2. Vitamin supplements cancel out this effect too.

That physical exercise induces muscles to make antioxidants appears to be because exercising muscles generate free radicals, the Germans conclude. Supplements containing high quantities of antioxidant vitamins may inhibit the production of free radicals, and thus undermine the positive effect of training on the body's own production of antioxidants.


This makes us wonder: do antioxidant vitamins also reduce the muscle building effect of strength training? It's not such a strange question. Sports scientists from Liverpool John Moores University reported back in 2006 that one gram of vitamin C delays muscle recovery after intensive training. [Br J Nutr. 2006 May;95(5):976-81.]

Proc Natl Acad Sci U S A. 2009 May 11. [Epub ahead of print].