BUFFALO, N.Y. – A study by researchers at the University at Buffalo 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, PhD, assistant professor, Department of Exercise and Nutrition Sciences, UB School of Public Health and Health Professions.
He says, “The study found that those who consumed four servings of dairy per day over a six-month period responded with a nine per cent reduction in plasma insulin and an 11 per cent 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.
Rideout says, “The study, while small, is an important contribution to the literature, as it followed subjects over a long time period – 6 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, they consumed their habitual diets and were randomly assigned 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 a period of six months.
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 says.
“But in HD-consumption groups, plasma insulin levels dropped by an average of nine per cent, and insulin resistance, as estimated by HOMA-IR (Homeostasis Model of Assessment-Insulin Resistance) was reduced by 11 per cent when compared to the LD groups.
“These results require verification from additional long-term studies with appropriate measures to increase subject retention,” Rideout says, “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 , PhD, RD; Heather Martin, RD, and Curtis B. Rempel, PhD, all of the Richardson Centre for Functional Foods and Nutraceuticals, University of Manitoba, and Richard W. Browne, PhD, Department of Biotechnical and Clinical Laboratory Sciences, University at Buffalo.
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