Flavonoid-rich foods linked to lowered diabetes risk

NEW YORK (Reuters Health) - Women with diets rich in foods like berries, chocolate, red wine and tea also have reduced inflammation and insulin resistance - a diabetes precursor, according to new UK research.

Flavonoids are chemical compounds found in colorful fruits and vegetables, and laboratory studies suggest they may offer a variety of health benefits.

“The aim of this study was to add more weight to these findings by starting to unravel how they work in humans,” said Aedin Cassidy, a nutrition researcher at the University of East Anglia’s Norwich Medical School, who led the study.

“Our previous studies have shown that these powerful bioactive compounds called flavonoids, present in berries and other foods like chocolate and wine, can reduce your risk of having a heart attack and of developing type 2 diabetes,” Cassidy told Reuters Health by email.

Cassidy and her colleagues wanted to see if a large group would show differences in diabetes risk, and other health markers, based on their flavonoid consumption.

The study involved 1,997 healthy women from TwinsUK, a nationwide registry of adult twin volunteers. The women ranged in age from 18 to 76, and about half were post-menopausal.

The women completed food questionnaires that were used to estimate their intake of six types of flavonoids. Cassidy and colleagues also calculated the womens’ total calorie intake and their body mass index (BMI), a measure of weight in relation to height.

The participants were also asked about their family medical histories, general lifestyle habits and physical activity levels.

The women’s average total flavonoid intake was 1.2 grams per day, but ranged from about 0.6 grams daily among women with the lowest intake to about 1.7 grams among women with the highest intake.

Tea was the biggest source of flavonoids in the women’s diets. They also got plenty from grapes, pears, wine, berries, oranges and peppers, Cassidy’s team reports in The Journal of Nutrition.

The researchers also measured blood levels of insulin, glucose and markers of inflammation for all the participants and used those measurements to calculate insulin resistance.

Considered an early sign on the path to type 2 diabetes, insulin resistance occurs when the body is unable to use the insulin it produces effectively to get blood sugar into cells.

All in all, women who consumed the highest levels of two particular types of flavonoid, anthocyanins and flavones, had the least insulin resistance and lowest levels of inflammation.

“We showed in population-based studies that higher habitual intakes of one class of flavonoids called anthocyanins, compounds responsible for the red/blue color of berries and other fruits and vegetables, can improve the way we handle glucose and insulin and reduce inflammation - a risk factor for heart disease and diabetes,” Cassidy said.

The study cannot prove that eating flavonoid-rich foods caused any reduction in inflammation or insulin resistance. The flavonoids could also be the mark of some other factor that accounts for the differences, like exercise or an overall healthy diet.

The study also did not follow the women to see who actually developed diabetes or heart disease.

More research is needed to test what these plant compounds do in the body and how much of them would need to be consumed to offer a health benefit.

Previous research suggests that berries are particularly important, according to Cassidy.

“This latest research shows that just one portion of flavonoid-rich berries every day was associated with better control of blood sugar levels and blood pressure. But small amounts of red wine and moderate amounts dark chocolate may aid prevention efforts as part of a healthy diet,” Cassidy said.

SOURCE: The Journal of Nutrition, online January 20, 2014.