Fashion trends from the 1990s may be making a comeback, but 1990’s dietary trends should definitely stay out of style. In that decade, fat was a four-letter word and non-fat and low-fat versions of foods were promoted over their full-fat counterparts, with the hope of improving heart health and reducing waist lines. We now know that trading fat for carbohydrates did not make Americans healthier (or thinner), but old habits die hard. Thirty years later, the influence of this fat-free mania on food choices and dietary recommendations is still evident. The most recent edition of the Dietary Guidelines for Americans recommends non-fat and low-fat milk, yogurt, and cheese to limit saturated fat intake. But far from clogging arteries and increasing cholesterol, a growing body of scientific studies suggests dairy-derived saturated fats could be beneficial for cardiovascular health.
The most recent vindication for dairy fats comes from data collected as part of the Women’s Health Initiative, one of the largest studies to address risk factors for cardiovascular disease. Detailed dietary data and blood samples were collected from over 35,000 post-menopausal women aged 50–79 from across the United States to test the hypothesis that dairy foods are associated with blood biomarkers commonly used to assess risk for cardiovascular disease and diabetes. These included markers for lipid metabolism (total triglycerides, low-density lipoprotein, high-density lipoprotein, and total cholesterol), inflammation (C-reactive protein, IL-6, IL-10, and TNF-α), and glucose metabolism (glucose and insulin-related factors).
Eating more dairy, including full-fat milk, cheese, and yogurt, was associated with a favorable biomarker profile. Going against the dogma that saturated fats are bad for heart health, higher intakes of full-fat dairy, cheese, and yogurt were associated with lower levels of blood triglycerides. And women with higher intakes of total dairy (all levels of fat), low-fat dairy, total cheese, and total yogurt also had lower levels of glucose, insulin, and two markers of inflammation (C-reactive protein and IL-6).
Of all the dairy foods included in the analysis [8], yogurt seemed to have a unique influence on biomarker profiles. Increased yogurt consumption was associated with the largest percentage decrease in blood glucose, insulin, C-reactive protein, and IL-6 concentrations, supporting previous research on the protective effects of yogurt on inflammation and diabetes. Additionally, yogurt intake—of all fat levels—was associated with an increase in high-density lipoprotein (HDL) cholesterol, and a decrease in total triglycerides and low-density lipoprotein (LDL) cholesterol. (For those needing a quick recap on cholesterol, LDL are proteins that move fat into the walls of the arteries and can lead to plaque, whereas HDL remove fats from the artery walls. Generally speaking, higher LDL increases the risk for cardiovascular disease, whereas lower LDL and lower triglycerides decrease the risk).
These additional effects of yogurt compared with other dairy foods are, at least in part, because yogurt is fermented and contains probiotic bacteria, like Lactobacillus. As yogurt is digested, these beneficial bacteria increase the concentration of biologically-active proteins, which then, in turn, could potentially influence physiological processes like glucose metabolism, lipid metabolism, and inflammatory reactions.
Cheese, another fermented dairy food, was also associated with favorable profiles. Looking at just yogurt and cheese, one could argue that fermented dairy might offer health benefits despite their saturated fat content. But the finding that full-fat dairy intake was associated with lower triglycerides, as well as lower insulin and glucose concentrations, suggests that dairy-derived saturated fats could actually be mediating these associations rather than simply riding the coattails of probiotics or other nutrients in dairy.
Milk fats are biologically different from those found in bacon or biscuits. Fats in milk are packaged in membrane-bound bubbles called globules (and are referred to as the milk fat globule membrane, or MFGM). Dairy fatty acids within the MFGM are shorter in carbon chain length relative to fatty acids from other animal fats, which could positively affect cholesterol by raising HDL levels. And new research suggests the MFGM interacts directly with microorganisms in the gut, which could then influence human physiology in much the same way as probiotics from fermented foods.
It seems counterintuitive that saturated fats could be heart healthy. After all, we have been inundated with dietary advice to limit or avoid them for decades precisely because of their association with cardiovascular disease. But it might be time for dietary advice to join the 21st century and focus on the biological effects of foods rather than nutrients. — By Lauren Milligan Newmark, Ph.D., International Milk Genomics Consortium