There are few foods for which dietary recommendations and popular ideology are as far apart as they are for dairy. The internet is full of warnings on the dangers of any and all dairy consumption, but (low-fat) dairy products are key components of research-supported healthy dietary patterns. Emerging research suggests a more nuanced approach to the dairy food group may be necessary.
Beyond Saturated Fat: Dairy products are rich sources of beneficial dietary calcium and added vitamin D, but dairy—except fat-free and low-fat (1%)—is also a top contributor of saturated fat in the U.S. diet, and higher amounts of saturated fat relative to mono- and polyunsaturated fats is associated with increased risk for heart disease and stroke. But looking at saturated fat content alone may not tell the whole story of dairy and health. “Dairy contains a complex mix of different fatty acids, plus vitamins and other constituents,” says Dariush Mozaffarian, MD, DrPH, dean of the Friedman School and editor-in-chief of Tufts Health & Nutrition Letter. “It can also be fermented (like cheese) or have live probiotics (like yogurt). Each of these factors can create varying biological effects.”
Dairy and Disease: “Milk, cheese, yogurt, and butter are all different foods, which may not impact health in the same way.,” says Mozaffarian. “Given the varying characteristics of different dairy foods, their health effects appear more closely related to the type of dairy, rather than low-fat vs. whole-fat alternatives.” For example, dairy products have varying levels of milk fat globule membrane, which contains specialized, biologically active fats called phospholipids. The presence of this membrane lowers cholesterol absorption in the gut and thus blood cholesterol levels and may play other roles in the health impacts of dairy foods; probiotics used to make yogurt may be beneficial to the gut microbiome; the fermentation of milk to produce cheese turns vitamin K into vitamin K2 (menoquinones) which may improve insulin secretion and sensitivity and has been associated with decreased risk of cardiovascular disease and cancer. Here is what the latest research says about dairy and disease:
Cancer: Calcium and dairy intake have been associated in some studies with lower risk of colorectal cancer, but higher risk of prostate cancer (especially dietary and supplemental calcium intake totaling more than 2,000 milligrams a day). In one study, high intake of lactose (the sugar found in milk) was associated with a moderately higher risk of ovarian cancer. Studies like these, while worrisome, do not prove cause and effect. To date, the American Cancer Society does not feel there is adequate information to make specific recommendations on calcium and dairy food intake to try to lower cancer risk.
Diabetes: In a recent analysis, higher blood levels of some dairy fats were associated with a significantly lower risk of diabetes. Additionally, a recent large cohort study suggests there may be potential benefits of dairy fat consumption, especially among younger adults and women, and particularly if the dairy fats replace other animal fats or refined carbohydrates in the dietary pattern. Because people with diabetes are at increased risk for heart disease, the American Diabetes Association recommends keeping saturated fat intake from all sources, including dairy, to less than ten percent of daily calories (less than 20 grams a day for a 2,000-calorie diet).
Cardiovascular Disease: The American Heart Association recommends saturated fats in the diet be largely replaced with mono- and polyunsaturated fats. To help limit saturated fat intake, low-fat and fat-free dairy products are recommended.
“We’re learning that the health effects of different dairy foods are tremendously complex,” says Mozaffarian, “and we’re just beginning to scratch the surface. Dairy foods represent a meaningful proportion of calories and nutrients for many around the world, creating an urgent need for additional careful research on dairy foods, their different characteristics, and effects on health.”