You know berries are really good for you—they’re always in those top 10 “superfood” lists. Now new research finds that specific antioxidants found in strawberries and cranberries improve insulin sensitivity—which in turn helps reduce diabetes risk. Does that mean that you can simply take these specific antioxidants as supplements or add them to foods or drinks—and skip eating all those berries? Let’s find out.
Background: Berries, rich in powerful antioxidants called polyphenols, have been linked with reduced diabetes risk in population studies. One hypothesis holds that polyphenols improve insulin sensitivity—the ability of the body to efficiently use the insulin it produces to manage blood sugar. That’s key to preventing or controlling diabetes. But it wasn’t known whether taking polyphenol supplements would do the trick, too.
Study: Canadian researchers studied 41 overweight men and women with prediabetes. They had impaired insulin sensitivity, which put them at high risk of developing diabetes. Every day for six weeks, half of the participants drank a no-calorie drink, rich in the specific polyphenols found in strawberries and cranberries. The commercial blend of polyphenol extracts provided an average daily dose of 333 mg of polyphenols—about what you’d get in about one-half cup of fresh berries. The other half of the participants consumed a polyphenol-free drink that looked and tasted the same. The participants continued to eat their normal diets but were asked to abstain from eating berries, drinking wine or taking polyphenol supplements of their own. Before and after starting the experiment, each participant had a series of tests to measure insulin sensitivity as well as markers of cardiovascular risk including cholesterol levels, inflammation and oxidation. It was a sponsored study, with funding from the manufacturer of the polyphenol blend, but it was conducted by independent university-based diabetes researchers.
Results: After six weeks, insulin sensitivity improved by 14% in the group given the polyphenol “cocktail,” but there was no significant change in the group given the placebo drink.
Surprising finding: No other changes were seen between the two groups—no difference in cholesterol levels, body-wide inflammation or oxidative status. That was surprising since population studies have linked eating more berries with less heart disease.
Bottom line: Strawberry and cranberry polyphenols, taken as supplements, can improve insulin sensitivity. (Other studies have found similar benefits in blueberries, too.) But the overall results of this study actually reinforce the benefits of eating whole berries. That’s because there’s a wealth of research suggesting that eating whole berries helps protect not only against diabetes but also heart disease and perhaps even dementia—yet no such cardiovascular benefits were seen in the study participants who consumed the polyphenol supplement. The researchers suggest that the lack of berry-based nutrients, especially fiber, may explain why the polyphenol-consuming group did not improve in other health heart-healthy measures. Berries not in season? Frozen berries are a great option—they are essentially identical to fresh berries in nutrition. Here’s an easy recipe for any-season no-sugar-added strawberry applesauce.