Heart Disease: Fat May Not Be the Villain
Emerging nutrition research is casting doubt on the prevailing theory that dietary fat, saturated fat and cholesterol are key players in the etiology of heart disease. In addition, recent research on dairy fat has shown no association with cardiovascular-related clinical outcomes and has proposed the idea that dairy fat may in fact be cardio-protective. But if total fat, saturated fat and cholesterol aren’t the villains they were once believed to be, how did the recommendations to limit them come about and how can you manage the topic of whole fat dairy with your patients and clients?
History of Total Fat Recommendations: Politics Versus Science
Over the past 50-plus years, dietary recommendations have included limits on total fat – appearing first in the dietary recommendations of the American Heart Association as “25-30% of calories from total fat” in the late 1950s. Thirty years later, the 1980 Dietary Guidelines for Americans recommended “avoiding too much total fat” and limiting it to 20-35% of calories, with most coming from unsaturated fats, such as fish, nuts and vegetable oils. While total fat has been a focus for over half a century, the conversation has shifted from the amount of fat to the type of fat and, similarly, a change from nutrient-based to a whole food or pattern-based approach to healthy eating.
How did recommendations to limit total fat remain in dietary guidelines for the last 40 years? Most nutrition scientists point toward Dr. Ancel Keys, an influential scientist known for his Seven Countries Study, which found an association between elevated total serum cholesterol levels and myocardial infarction (MI). Dr. Keys incorrectly put forth the idea that this association showed that dietary fats caused an increase in blood lipids. Based on this research, he persuaded the American Heart Association to include reducing total dietary fat and saturated fat in their initial guidelines. Later analysis of his study, however, found that his research was not representative, and he had only included data from countries that supported his hypothesis (7 out of 22), hence the name Seven Countries Study.
What We Know About Dietary Fat Has Changed
In 1970, British nutritionist John Yudkin was one of the first scientists to oppose Dr. Key’s findings by proposing that sugar was the leading cause of heart disease in wealthy nations. However, it wasn’t until 2008 that the Food and Agriculture Organization and the World Health Organization stated, “there is no probable or convincing evidence for significant effects of total dietary fats on coronary heart disease or cancers.” Today, research on the Mediterranean diet now shows that people who consume diets rich in olive oil and nuts that are higher in total fat have reduced outcomes of acute MI, stroke or death compared with those who consumed a lower-fat control diet.
The Story Is Similar for Saturated Fat and Cholesterol
The classic lipid hypothesis of cardiovascular disease holds that dietary saturated fat raises blood cholesterol, in turn increasing the risk of heart disease. But the published literature of the past few years indicates it’s not that simple and all saturated fats are not necessarily equal. They have very different biologic effects, and the food matrix in which they occur seems to be important. Still, the 2015-2020 Dietary Guidelines for Americans recommends consuming “less than 10% of calories per day from saturated fats,” without acknowledging the complexities.
Dietary cholesterol, on the other hand, is seeing shifts in the recommendations. What was once considered a nutrient of concern and limited to less than 300 milligrams per day, now has no limitation. For the first time, the 2015-2020 Dietary Guidelines for Americans did not set a limit for dietary cholesterol and states, “Adequate evidence is not available for a quantitative limit for dietary cholesterol.”
What Does Recent Science Say About Dairy?
Overall, the growing body of evidence indicates that dairy food intake, regardless of fat level, is not associated with higher risk of cardiovascular disease, coronary heart disease or stroke – and in some cases, consumption is associated with a lower risk.
The studies below contribute to the body of evidence that enhances our understanding of the link between dairy food consumption and risk of cardiovascular disease (CVD).
- 2020 Expert Review: States that “emerging evidence shows that the consumption of full-fat dairy foods has a neutral or inverse association with adverse cardiometabolic health outcomes, including atherosclerotic cardiovascular disease, type 2 diabetes and associated risk factors.”
- 2018 Prospective Cohort Study: Concluded higher dairy food consumption is associated with a lower risk of mortality and cardiovascular disease, particularly stroke.
- 2016 Systematic Review: Found cheese is associated with a reduced risk of CVD, congenital heart defects and stroke.
- 2016 Systematic Review: Indicates that “the consumption of various forms of dairy products shows either favorable or neutral associations with cardiovascular-related clinical outcomes.”
- 2015 Journal of Nutrition Study: Determined that total and especially full-fat dairy food intakes are inversely and independently associated with metabolic syndrome in middle-aged and older adults.
- 2015 Atherosclerosis Research Program Study: Concluded “There is growing evidence that SFAs [saturated fatty acids] in the context of dairy foods, particularly fermented dairy products, have neutral or inverse associations with CVD.”
- 2010 Prospective Case-Control Study: Concluded that milk fat biomarkers were associated with a lower risk of developing a first MI, especially in women.
How Can You Manage the Topic of Whole Fat Dairy With Your Patients and Clients?
Bottom line: The totality of available scientific evidence supports the intake of milk and dairy products, regardless of fat content, and underscores the potential of dairy foods as part of a balanced diet to protect against the most prevalent chronic diseases; whereas, very few adverse effects have been reported. Based on this, doctors, dietitians and other health professionals can feel comfortable recommending either whole fat or low-fat milk, cheese and yogurt to their patients and clients as part of a balanced and nutritious eating pattern.