Diabetes Self-Management Blog

It’s all over the Web: A new study has found that antioxidants — vitamins and other substances that protect cells against the effects of harmful, highly reactive oxygen molecules — may increase insulin resistance, a hallmark of Type 2 diabetes.

The study, according to a Reuters article, suggests that oxidative stress (caused by the harmful oxygen molecules) may serve a useful purpose. This seemingly harmful effect was found to inhibit the release of enzymes that make the body’s cells less sensitive to insulin. But there are a couple of catches: The study was done on mice, and the negative effects of antioxidants were seen in mice bred specifically to lack an enzyme that fights oxidative stress. Results in mice are not, of course, always seen in humans: Humans are far more complex organisms than mice, as anyone following the progress of Type 1 diabetes research in rodents is probably aware. And although using mice that lack an oxidative stress–fighting enzyme might approximate humans with a similar resistance to diet-induced insulin resistance (the mice in the study were overfed, which usually leads to insulin resistance), it is likely that a broader variety of factors affect how susceptible a human is to insulin resistance and Type 2 diabetes.

The new study does have some company among human trials, however. Earlier this year, we wrote about a study that found supplements of antioxidant vitamins C and E to reduce the insulin-sensitizing effect of exercise. Those researchers concluded that the antioxidants prevented the body’s natural defense mechanism against exercise-induced oxidative stress from taking place — a mechanism that, when in effect, leads to greater insulin sensitivity.

But studies of pills and supplements are only part of the story. For reasons not entirely understood, the body often does not absorb or use some vitamins and nutrients the same way when they are ingested in pill form as when they are obtained naturally through food. A study published in August found that taking antioxidant supplements did not help prevent metabolic syndrome (a condition characterized by insulin resistance, high blood pressure, abnormal blood lipid levels, and obesity). However, having high blood levels of certain antioxidants at the beginning of the study — which the researchers believed indicated more consumption of fruits and vegetables — did predict a lower risk of metabolic syndrome. And a study published yesterday found that access to fruits and vegetables, among several other factors, is associated with a lower risk of Type 2 diabetes. (For more information on the evidence surrounding antioxidants, check out “Antioxidants: Should You Supplement?”)

Do you take any antioxidant supplements? Are you convinced by this study — or by any other — that taking antioxidant supplements might be a bad idea? What antioxidant-rich foods, if any, do you try to include in your diet? Leave a comment below!


  1. I’ve been taking antioxidants for over 30 years before they were know as antioxidants.

    Posted by Harry......................... |

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