High dairy consumption may improve insulin resistance

Love that yogurt? Have another bowl. In fact, have four.

A study by researchers at UB and the University of Manitoba has found that consumption of high amounts of low-fat dairy food over a six-month period improved a marker of insulin resistance in healthy adults but had no ill effect on body weight and composition, energy expenditure, blood pressure, blood glucose, and blood lipid and lipoprotein responses.

The study was published in the May 2013 issue of Nutrition Journal.

The lead author is Todd C. Rideout, assistant professor, Department of Exercise and Nutrition Sciences, UB School of Public Health and Health Professions.

“The study found that those who consumed four servings of dairy per day over a six-month period responded with a 9 percent reduction in plasma insulin and an 11 percent reduction in an established marker of insulin resistance, which is the inability of the body to utilize the hormone insulin properly,” Rideout says.

“There is a good deal of debate about the role of dairy consumption on biomarkers of metabolic syndrome and a number of studies have considered that role under different conditions.”

Metabolic syndrome, or insulin-resistance syndrome, is a combination of medical disorders that increases the risk of developing cardiovascular disease and diabetes. Twenty-five percent of Americans have the syndrome and its prevalence increases with age.

“The study, while small, is an important contribution to the literature,” Rideout says, “as it followed subjects over a long time period—six months—compared with the short (one month) duration of most published investigations.

“Our study was designed to specifically examine the effects of low-fat milk and yogurt products. This is important, as different dairy foods have been shown to elicit differential metabolic responses. Determining the specific health benefits of specific dairy products and isolated dairy bioactive components will be critical issues of future dairy-based research,” he says.

“The study used 23 healthy subjects ages 18 to 75 assessed to be healthy based on a pre-study screening,” he says. “They completed a randomized, crossover trial of 12 months.”

For the first six months, subjects consumed their habitual diets and were assigned randomly to one of two treatment groups: a high-dairy group (HD), which supplemented its diet with four servings of dairy (restricted to low-fat milk or low-fat yogurt products) a day, or a low-dairy group (LD), which supplemented its diet with no more than two servings of low-fat dairy a day.

For the second six months of the study, the HD group ate a low-dairy diet and the LD group ate a high-dairy diet. During both parts of the study, baseline, midpoint and endpoint metabolic responses were examined.

“We found that endpoint measurements of body weight and composition, energy expenditure, blood pressure, blood glucose, and blood lipid and lipoprotein responses were the same in LD and HD groups,” Rideout explains.

 “But in HD-consumption groups, plasma insulin levels dropped by an average of 9 percent, and insulin resistance, as estimated by HOMA-IR (Homeostasis Model of Assessment-Insulin Resistance) was reduced by 11 percent when compared to the LD groups.

“These results require verification from additional long-term studies with appropriate measures to increase subject retention,” Rideout stresses, “and future studies should also be designed to further examine the metabolic effects of specific dairy products and/or dairy-derived bioactive components.”

Study co-authors are Christopher P.F. Marinangeli, Heather Martin and Curtis B. Rempel, all of the Richardson Centre for Functional Foods and Nutraceuticals at the University of Manitoba, and Richard W. Browne of the UB Department of Biotechnical and Clinical Laboratory Sciences.