Antioxidants in Diet Can Improve Insulin Sensitivity: New Study

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Preliminary research from Italy indicates that regularly eating foods that are rich in antioxidants (substances that help protect cells from oxidative damage) can improve insulin sensitivity and enhance the effects of the diabetes drug metformin in obese adults with insulin resistance. Insulin resistance, a condition in which the body requires extra insulin to maintain normal blood glucose levels, is a hallmark of Type 2 diabetes.

The study, presented at the Endocrine Society’s 92nd Annual Meeting, looked at 16 men and 13 women, ages 18 to 66, who were obese and insulin resistant but who did not have diabetes. The participants were randomly assigned to one of four treatment groups. Group A followed a Mediterranean-style diet with roughly 1,500 calories daily composed of about 25% protein and 75% low-glycemic-index carbohydrates; Group B followed the same diet but also took metformin; Group C followed the Mediterranean-type diet supplemented with 800–1,000 milligrams per day of antioxidants provided by fruits and vegetables; and Group D followed the antioxidant-supplemented meal plan and also took metformin.


On average, all the groups lost similar amounts of weight. However, only people in the two groups receiving supplemental antioxidants from fruits and vegetables showed a significant decrease in insulin resistance. Those in the group receiving both antioxidants and metformin showed the greatest improvement in insulin resistance based on their response to an oral glucose tolerance test.

According to lead study author Antonio Mancini, MD, “The beneficial effects of antioxidants are known, but we have revealed for the first time one of their biological bases of action — improving hormonal action in obese subjects with the metabolic syndrome… We think that a total antioxidant level of 800 to 1,000 milligrams a day is safe and probably not close to the maximum tolerable level.”

Mancini and his team note that further study is required to explain the mechanisms behind the antioxidants’ apparent improvement of insulin sensitivity.

For more information, read the article “Well-Defined Quantity of Antioxidants in Diet Can Improve Insulin Resistance, Study Finds.” And to learn more about antioxidants, see the article “Antioxidants: Should You Supplement?”

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