May 13, 2009
Vitamins C, E Reduce Exercise Benefits

Quenching too many free radicals with antioxidant vitamins can increase risk of insulin-resistant diabetes.

A study published today in the "Proceedings of the National Academy of Sciences" (PNAS) suggests that vitamin C and E supplements may actually be harmful, at least in regards to diabetes risk and glucose metabolism. According to this study, the health-promoting effects of exercise require the formation of oxidative stress during sports and if this is blocked, some of these effects do not occur. In the particular study, the intake of antioxidants during a four-week exercise training class abolished the effects of exercise to improve insulin sensitivity and glucose metabolism which would help prevent diabetes, while those individuals not taking the antioxidants had major benefits in terms of metabolism from exercise.

Dr. Michael Ristow, lead-author of the study which was published by a team of researchers from Leipzig and Jena Universities (both Germany) and Harvard Medical School, points out: "Exercise causes repeated boosts of free radicals, which - according to our results - induce a health-promoting adaptive response in humans. Subsequently, our body activates molecular defense systems against stress, and metabolizes carbohydrates more efficiently, both of which prevents diabetes, and possibly other diseases. Blocking these boosts of free radicals by antioxidants accordingly blocks the health promoting effects of exercise." He further says that "short-term doses of free radicals may act like a vaccine, helping the body to defend itself from chronic stressors more efficiently by inducing a long-term adaptive response".

Dr. C. Ronald Kahn, a collaborating author from the Joslin Diabetes Center and Harvard Medical School, noted: "This is a very important study for the millions of people at risk for type 2 diabetes. Exercise is a proven way to improve insulin action and reduce diabetes risk, but clearly this beneficial effect can be largely blocked by taking these very commonly used vitamin supplements. We need larger studies to fully assess this effect, but in the meantime, individuals at risk for diabetes and maybe even some with type 2 diabetes itself, need to think carefully about the use of these vitamin supplements, especially if they exercise regularly to improve there health."

This result isn't surprising because free radicals work as signaling agents in the body. Denman Harman, the guy who originally proposed the free radical theory of aging back around 1955, said if you take too much antioxidant vitamins you will feel slugging because you'll basically damp down your metabolism. That was his own personal experience (as related in an interview I can no longer find on the web btw).

So use of antioxidant vitamins brings trade-offs. How to figure out optimal doses? The doses used in this study are in line with what a lot of people take.

For the study, Ristow and colleagues observed two groups of young men during four weeks of intensive exercise training. One group took a combination of vitamin C (1000 mg/day) and vitamin E (400 IU/day) while the other did not.

The men who took the supplements showed no changes in their levels of ROS, whereas those who did not showed increased levels of ROS and oxidative stress.

The vitamins suppress a free radical indicator called TBARS.

Muscle biopsies showed a two-fold increase in a marker of free radicals called TBARS (thiobarbituric acid-reactive substances) in those volunteers who didn't take antioxidants, but no increase in those who did take the supplements suggesting that they were indeed mopping them up.

What we need: a pill that will simulate the effects of exercise without causing free radical damage. Then we can sit as couch potatoes and live longer than exercisers.

Share |      Randall Parker, 2009 May 13 07:14 AM  Aging Exercise Studies

Jake said at May 14, 2009 7:28 AM:

Another defective study due to the ignorance of the researchers.

A fatal flaw in this study is the "hyperinsulinemic euglycemic clamp" test they used to determine "insulin sensitivity". Nothing is wrong with the test, it's just that you can't use it the same way on someone who has ingested vitamin C. This test involves giving someone insulin and then seeing how much glucose is needed to maintain blood sugar. More glucose required is a good sign that you are "insulin sensitive". The problem is that vitamin C makes you more sensitive to insulin, elevates glucose, reducing the need for sugar, which would make it appear as a negative outcome:

as said at May 14, 2009 10:51 AM:

Hi Randall,

This is somewhat off topic, but I'm wondering about fish oil supplements and whether they are good for you.

There's a guy Ray Peet who has written an article "The Great Fish Oil Experiment" in which he says that fish oils, which are polyunsatured, oxidize easily and so aren't good for.

He also says to go easy on the oily fish.

The Eskimos, who eat a ton of salmon, eat it raw, correct? Is it okay to cook oily fish? Won't that oxidize the fats? And isn't that bad?

Jeff said at May 14, 2009 9:17 PM:

Here's a study which draws the exact opposite conclusion of the PNAS paper:

The study subjects who received vit.C, vit.E, and beta-carotene had less oxidative stress and INCREASED insulin sensitivity. It is unlikely you'll read about it in the pharma-sponsored MSM with its anti-supplement bias.

Randall Parker said at May 14, 2009 10:01 PM:


If vitamin C causes an elevation of blood glucose isn't that a bad thing?


If omega 3 fatty acids shorten lifespans then I'd like to see a population study that shows a negative correlation between omega 3 consumption and life expectancy.

Cooking fats: Temperature and length of time exposed to heat matter.

Nerissa Belcher said at May 15, 2009 1:03 AM:

Future Pundit: "What we need: a pill that will simulate the effects of exercise without causing free radical damage. Then we can sit as couch potatoes and live longer than exercisers."

Simple - take a pill, just about any pill, every other day. Just don't take in much of anything else that day. I.E. do intermittent fasting. It lowers free radicals while duplicating many of the health effects of exercise. For example:

"J Nutr Biochem. 2009 May 6
Cardioprotective effect of intermittent fasting is associated with an elevation of adiponectin levels in rats.
Wan R, Ahmet I, Brown M, Cheng A, Kamimura N, Talan M, Mattson MP.
Laboratory of Neurosciences, National Institute on Aging, Intramural Research Program, National Institutes of Health, Baltimore, MD, USA.
It has been reported that dietary energy restriction, including intermittent fasting (IF), can protect heart and brain cells against injury and improve functional outcome in animal models of myocardial infarction (MI) and stroke. Here we report that IF improves glycemic control and protects the myocardium against ischemia-induced cell damage and inflammation in rats. Echocardiographic analysis of heart structural and functional variables revealed that IF attenuates the growth-related increase in posterior ventricular wall thickness, end systolic and diastolic volumes, and reduces the ejection fraction. The size of the ischemic infarct 24 h following permanent ligation of a coronary artery was significantly smaller, and markers of inflammation (infiltration of leukocytes in the area at risk and plasma IL-6 levels) were less, in IF rats compared to rats on the control diet. IF resulted in increased levels of circulating adiponectin prior to and after MI. Because recent studies have shown that adiponectin can protect the heart against ischemic injury, our findings suggest a potential role for adiponectin as a mediator of the cardioprotective effect of IF.
PMID: 19423320."

Also see and .

pjnoir said at June 12, 2009 2:32 PM:

hack research

Aniika said at November 27, 2010 9:12 AM:

Although I agree with the above commenter that diets using a zig-zag type calorie intake like bodybuilders prefer and that popular diet plans such as utilize is a better way to trick your body into elevating metabolism. I think that vitamins and the such are vital to maintain optimum health and regardless of how much weight you lose (which after all is what most people are concerned with) you should still be taking them.

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