Published June 28, 2013
A diet that includes plentiful low-fat dairy foods improves measures of insulin resistance, according to a study by University at Buffalo researchers and their Canadian colleagues.
Such a diet also has no ill effect on several other health measures, including body weight, the researchers found.
While small, both the length of the study and its specific nature make it “an important contribution to the literature,” notes the study’s lead author Todd C. Rideout, PhD, assistant professor of exercise and nutrition sciences in the UB School of Public Health and Health Professions.
Results are based on six months of follow-up, compared to one month for most published studies, he says.
Also, the study was designed to examine the effects of specific dairy foods—a key to beneficial research, he says. (Only low-fat milk and yogurt were assessed.)
The crossover study involved 23 healthy subjects.
For the first six months, a randomly assigned group supplemented their usual diet with four daily servings of low-fat milk or yogurt; the remaining group ate up to two servings.
For the next six months, participants switched diets: the original high-dairy group ate a low-dairy diet while the initial low-dairy group consumed a high-dairy diet.
Metabolic responses were measured at the beginning, middle and end of each six-month period.
Compared to their low-dairy counterparts, the high-dairy participants reduced plasma insulin by an average of 9 percent and reduced Homeostasis Model of Assessment-Insulin Resistance by 11 percent.
Other health measures stayed the same, including body composition, energy expenditure, blood pressure, blood glucose, and blood lipid and lipoprotein responses.
Further study may reveal what led to the health benefits realized in the study, notes coauthor Richard W. Browne, PhD, associate professor of biotechnical and clinical laboratory sciences, who performed all the biomarker measurements.
“Although the standard lipid profile was the same in both the low-dairy and high-dairy groups, a more detailed analysis of bioactive lipid metabolites, including cholesterol and fatty acid oxidation products, may provide clues to the mechanism behind the reduction in insulin resistance,” he says.
Reliable dietary information that could help reduce insulin resistance would have significant public health benefits.
Insulin resistance—the body’s inability to utilize the hormone insulin properly—can presage major health complications, explains Rideout.
One-fourth of Americans (nearly 80 million) have metabolic or insulin-resistance syndrome—and its prevalence increases with age.
The syndrome involves a combination of medical disorders that increase the risk of developing cardiovascular disease and diabetes.
Prior research on dairy products has not always yielded clear, useful findings.
“There is a good deal of debate about the role of dairy consumption on biomarkers of metabolic syndrome,” Rideout acknowledges.
A number of studies have considered that role under different conditions, and different dairy foods have been shown to elicit differential metabolic responses,” he explains.
Therefore, critical issues of future dairy-based research must involve “determining the specific health benefits of specific dairy products and isolated dairy bioactive components.”
Rideout says his own results won’t necessarily translate into dietary advice for the general public. “We need verification from additional long-term studies with appropriate measures to increase subject retention,” he says.
The study, “Consumption of Low-Fat Dairy Foods for 6 Months Improves Insulin Resistance without Adversely Affecting Lipids or Bodyweight in Healthy Adults: A Randomized Free-Living Cross-Over Study,” has been published in Nutrition Journal.
The UB researchers collaborated with three colleagues at the Richardson Centre for Functional Foods and Nutraceuticals at the University of Manitoba in Winnipeg.