Facts, Not Fads: Dairy Fat Can Be Heart Healthy

Written by: Lauren Milligan Newmark, Ph.D. | SPLASH! Issue # 113 | 2023

If your New Year’s resolution for 2023 was to eat healthier, you’re not alone. Fifty percent of Americans surveyed at the end of 2022 planned to use the change in calendar year to make improvements to their diet [1]. With so much dietary advice available at the click of a mouse, it can be difficult to discern diet fads from scientifically informed guidance. The Dietary Guidelines for Americans (DGA) [2] were designed to help us separate the wheat from the chaff when it comes to healthy eating choices across the life span. But despite being based on “the most current body of nutritional science” [2], the recent edition of the DGA falls short of their promise when providing guidance on dairy foods.

To combat cardiovascular disease (CVD)—the leading cause of death for Americans—the current DGA recommends avoiding full-fat dairy foods in favor of low- or non-fat versions [2]. This guidance incorrectly implies that all dietary sources of saturated fat have a negative effect on heart health [3]. Instead, different saturated fat-containing foods can have different health effects [3, 4]. Previous research has shown dairy-derived saturated fats have neutral or even positive effects on body fat, cholesterol, heart disease, and numerous biomarkers associated with cardiovascular health [3].

More evidence that full-fat dairy can be part of your 2023 healthy eating plan comes from a new study [4] investigating the relationship between dairy fats and dyslipidemia, a condition of high cholesterol and high levels of triglycerides (“fat”) in the blood. The study participants (n = 2,391) were a subset of the Framingham Offspring cohort, a group of adults that have provided dietary and heart health data since the early 1970s. For each participant, specific amounts of dairy-derived saturated fats and non-dairy saturated fats were calculated from two sets of 3-day diet records provided between four and seven years apart [4]. Then, roughly four years and eight years after the second set of dietary data were collected, each participant’s weight and height were recorded and each provided a fasting blood sample that was analyzed for two markers of inflammation (C-reactive protein, fibronectin); cholesterol, including low-density lipoprotein (LDL), high-density lipoprotein (HDL), and very-low-density lipoprotein (VLDL); particle sizes for all types of cholesterol; and triglycerides (TG) [4].

This may seem like data overkill, but there is good reason for measuring so many factors. Cardiovascular health cannot be assessed by just checking cholesterol; LDL and HDL levels are also important. For example, someone with high LDL but also high HDL has a reduced CVD risk compared with someone with high LDL and low HDL. And then within the low- and high-density dichotomy, particle size matters as well. Saturated fats that increase small LDL particle size pose a larger risk to CVD than do those that increase larger LDL molecules [3, 5, 6]. Finally, inflammation is also a risk factor for CVD—it is possible for dietary fats to have a neutral effect on blood lipids while positively or negatively influencing the production of markers of inflammation [3].

Participants with the highest intakes of dairy-derived saturated fat had blood profiles associated with low risk for dyslipidemia and inflammation [4]. Interestingly, the specific associations depended on participant sex. Male participants with higher mean intakes of dairy-derived saturated fats had a lower CVD risk profile: lower levels of inflammation markers, higher HDL cholesterol, lower VLDL concentrations, larger LDL and HDL particle size, and lower TG concentration [4]. Among females, higher mean intakes of saturated fat from dairy foods were associated with lower levels of body fat, but there was no significant association with inflammation biomarkers. In both males and females, higher intakes of saturated fat from dairy were associated with a lower TG:HDL ratio [4].

The Framingham Offspring Study was prospective in design, meaning it can demonstrate an association between dairy-derived saturated fat and lower CVD risk but cannot prove that saturated fat from dairy foods is the cause for lower cholesterol, lower TG, or less inflammation. However, the length of the study period, representing nearly 16,000 days of food intake, and the specific focus on separating saturated fat intake from other dietary sources of saturated fat strengthen the validity of the identified associations. It was not immediately clear to the study team why they observed sex differences in the strength of their associations. Future studies will help determine if saturated fats have different physiological effects in males compared with females or if there was a confounding factor that the Framingham study failed to account for.

For those that grew up with the dogma that all saturated fats were artery cloggers, the cardiovascular benefits of full-fat dairy may be hard to swallow. The stigma of saturation is strong—but if dark chocolate can become a health food, so can whole milk! Saturated fats from dairy foods are unique because they contain more short- and medium-chain fatty acids than do fats from other animal sources. These fatty acids have different metabolic effects, potentially raising HDL cholesterol more effectively than fatty acids with longer chains of carbons [5]. And unlike a hamburger, dairy-derived saturated fats are delivered with minerals and bioactive peptides that have positive health effects such as lowering blood pressure and reducing inflammation. The most successful New Year’s resolutions are ones that don’t require an entire overhaul of people’s lifestyles. The same is true for nutritional advice. Rather than revise the guidelines to encourage full-fat dairy intake, a more successful solution could be to remove guidance about fat content; simply encourage Americans to meet their daily dairy intake without specifying the type of fat [7]. Food-based rather than fat-based nutritional guidance will hopefully become a dietary fad that sticks.

References

1. https://www.statista.com/chart/29019/most-common-new-years-resolutions-us/
2. U.S. Department of Health and Human Services and U.S. Department of Agriculture. 2020-2025 Dietary Guidelines for Americans. 9th Edition. December 2020. Available at https://www.dietaryguidelines.gov/sites/default/files/2020-12/Dietary_Guidelines_for_Americans_2020-2025.pdf
3. Sendra E. Dairy fat and cardiovascular health. Foods. 2020 Jun 26;9(6):838.
4. Yuan M, Singer MR, Pickering RT, Moore LL. Saturated fat from dairy sources is associated with lower cardiometabolic risk in the Framingham Offspring Study. The American Journal of Clinical Nutrition. 2022 Dec; 116(6):1682-92.
5. de Oliveira Otto MC, Mozaffarian D, Kromhout D, Bertoni AG, Sibley CT, Jacobs DR Jr, Nettleton JA. Dietary intake of saturated fat by food source and incident cardiovascular disease: the Multi-Ethnic Study of Atherosclerosis. The American Journal of Clinical Nutrition. 2012; 96(2):397-404.
6. Mozaffarian D. Saturated fatty acids and type 2 diabetes: more evidence to re-invent dietary guidelines. The Lancet Diabetes and Endocrinology. 2014; 2(10):770-772.
7. McGovern C, Rifas-Shiman SL, Switkowski KM, Woo Baidal JA, Lightdale JR, Hivert MF, Oken E, Aris IM. Association of cow’s milk intake in early childhood with adiposity and cardiometabolic risk in early adolescence. The American Journal of Clinical Nutrition. 2022 Aug; 116(2):561-71.

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