Diabetes Self-Management Blog

Many people who have Type 2 diabetes, or are at risk of developing it, are told to get more exercise. Research has shown that exercise can reduce insulin resistance (a hallmark of Type 2 diabetes) in addition to its cardiovascular benefits and proven ability to help maintain weight loss.

But a new study suggests that the insulin-sensitizing effect of exercise could be undone by vitamin pills. Published in the journal Proceedings of the National Academy of Sciences, the study tested insulin sensitivity in healthy young men before and after a four-week exercise program. One group was assigned to take a combination of vitamins C and E; the other group did not take any vitamins. At the end of the four weeks, insulin sensitivity had improved only in men who were not taking the vitamins.

Researchers concluded that the vitamins in the study neutralized potentially harmful oxygen molecules released by the body during exercise (hence these vitamins are considered antioxidants). But this prevented the body’s natural defense mechanism against the oxygen from kicking in — a mechanism that normally leads to greater insulin sensitivity.

No single study is definitive, of course, as a representative for the dietary supplement industry reminds readers in a New York Times article about the study.

Do you take vitamin C or E, or another antioxidant supplement? How — if at all — has exercise affected your diabetes? Will you change your behavior based on this study? Leave a comment below!


  1. Yikes,

    I take an Omega supplement and green tea extract suplement. Would these contribute to any kind of ‘blocking’ as identified in the article?

    Posted by JLFarrell |
  2. I was told there were only 20 individuals involved. Take it for what its worth.

    Personally, I think we T1s need to suppliment because we lose so much in daily living.


    Posted by bhakti lila |
  3. I take several vitamins - multi, C, D, B6, as well as Omega3 fish oil, & cinnamon capsules. I don’t plan to change these unless/until definitive study published and my doc agrees.

    Posted by Dave |
  4. I am a type 1 diabetic for 45 years. I have been taking a product JUICE PLUS+ for 16 years. It is 17 different fruits and vegetables in a capsule. It is a whole food supplement not a vitamin.
    Posted by Lynda|May 21,2009 at 9:14pm

    Posted by Lynda Williamson |
  5. This article said nothing about the effects on women. Also how many people where in the study, and is 4 weeks truely a length of time to study andything medically. Too many questions to take any serious thinking on the study.

    Posted by Lee |

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