For decades, we were told to choose low-fat dairy. New research says otherwise
A new Canadian study led by University of Toronto professor Harvey Anderson adds to growing evidence that full-fat dairy can be part of a healthy diet.
In the 12-week study, 74 adults consumed different amounts of dairy under varying dietary conditions. The researchers found that eating three servings of full-fat dairy per day did not negatively affect body weight, body composition, energy metabolism, or blood lipid levels. The findings were recently published in The Journal of Nutrition.
Why Full-Fat Dairy Has Long Raised Concerns
Dairy foods contain saturated fat, which has traditionally been associated with higher cholesterol and an increased risk of cardiovascular disease. As a result, dietary recommendations in Canada and many other countries have typically encouraged people to choose fat-free or low-fat dairy products as a way to reduce saturated fat intake.
Anderson, a professor of nutritional sciences at U of T's Temerty Faculty of Medicine, says the evidence from human research has not always matched those concerns. Numerous human studies have found no link between eating full-fat dairy and harmful health outcomes. Some studies, including recent research led by Temerty Medicine professor Kozeta Milliku, have even reported positive or protective effects associated with dairy consumption.
Testing Three Daily Servings of Dairy
For the current study, researchers randomly assigned 74 adults with overweight or obesity to one of three dietary groups. One group followed a low-dairy, calorie-restricted diet. A second group followed an energy-neutral diet that included three servings of dairy each day. A third group ate an unrestricted diet that also included three daily servings of dairy.
All participants received guidance on following Canada's food guide, and those assigned to the dairy groups were supplied with full-fat dairy products during the study.
After 12 weeks, researchers found no meaningful differences in weight gain, body composition, or cholesterol levels between people following the low-dairy diet and those eating three servings of dairy each day. Participants consuming more dairy, however, showed improvements in blood pressure and consumed more calcium, protein, and vitamin D.
"Those that had three servings of dairy didn't have adverse levels of blood cholesterol or lipids or evidence of insulin resistance," says Anderson.
Why Dairy May Behave Differently Than Saturated Fat Alone
The apparent mismatch between the expected harms of saturated fat and the neutral or beneficial effects seen in some dairy studies may be explained by what researchers call the dairy matrix hypothesis.
This idea suggests that the physical structure of dairy foods influences how their nutrients are digested, absorbed, and ultimately affect the body. In other words, the health effects of a food may depend on how its components interact rather than simply on the amount of one nutrient it contains.
"With dairy products, it's got two proteins -- casein and whey -- that are bound together with fat and with nutrients mixed in," says Anderson.
According to Anderson, this complex structure allows nutrients in dairy foods to be delivered to the body gradually. That may help explain why the effects of eating dairy can differ from what would be predicted by looking at saturated fat or other individual nutrients in isolation.
Potential Importance for Older Adults
Anderson says the findings may be particularly important for older adults. Because people generally require less energy as they age, some may struggle to consume enough protein and other essential nutrients while keeping their overall calorie intake appropriate.
For many older adults, dairy is already a familiar food that provides substantial amounts of energy, protein, and other nutrients. Anderson says it could therefore offer a practical way to help meet nutritional needs without increasing the risk of diabetes or other chronic diseases.
More broadly, the results support an approach to nutrition research and dietary guidance that considers whole foods rather than judging foods primarily by individual nutrients.
With nutrition trends constantly changing and dietary advice sometimes appearing contradictory, Anderson offers a simple message: "Keep it simple, eat a variety of foods and not too much of anything."
This research was supported by Dairy Research Cluster 3 under the Canadian Agricultural Partnership AgriScience Program, and the Mitacs Accelerate program.
Reporting from ScienceDaily contributed to this story.
