“Isn’t it pretty to think so.”
Ernest Hemmingway concluded his 1926 classic novel The Sun Also Rises with this powerful statement of wistful longing for an alternative reality.
His quote came to mind as I read the recent headlines of the PURE study which claims that including whole-fat dairy as part of a healthy eating plan is associated with a lower risk for cardiovascular disease. Before running out to the grocery store to buy whole-fat dairy products, let’s take a critical look at the science behind the claim. First, we’ll look at dairy foods in general, then review the evidence around saturated fats, consider a landmark population health study, and finally, specifically evaluate the Prospective Urban Rural Epidemiology (PURE) Healthy Diet score study.
Nutritional Contribution of Dairy Foods
The broad category of dairy foods contains a multitude of beneficial nutrients. They are excellent sources of calcium, a mineral essential for building and maintaining strong bones and teeth. Additionally, dairy foods provide high-quality protein necessary for muscle growth and repair. Fermented dairy products, such as yogurt, and kefir contain probiotics that support gut health. Dairy foods are also rich in vitamins like vitamin D, which aid in calcium absorption and play a crucial role in immune function. While some may argue the need for these important nutrients from animal sources, the controversy making headlines is with the type of fat in the dairy products consumed.
Saturated Fat and Cardiovascular Risk
Diet modification has been the cornerstone of lifestyle modifications recommended for reducing cardiovascular disease risk. Reducing saturated fat intake has consistently been shown to be beneficial in reducing heart disease risk because of saturated fats’ positive association with elevated levels of LDL (low-density lipoprotein) cholesterol in the bloodstream. High intake of saturated fats from sources like red meat, full-fat dairy products, and certain tropical oils can contribute to the buildup of plaque in arteries. This buildup narrows and stiffens the arteries, impeding blood flow and increasing the chances of heart attacks or strokes.
Lowering the Cardiovascular Disease Burden in Finland
The benefit of lowering saturated fat is well demonstrated on a population level in the FINRISK study. In the 1970s, Finland embarked on a pioneering campaign to lower the incidence of cardiovascular disease, which were among the highest in the world. The Finnish government and health authorities implemented a comprehensive strategy originally known as the North Karelia Project, targeting key risk factors like smoking, poor diet, and high blood pressure. The initiative was then expanded to include the entire country. Efforts included widespread public health education, and specifically advocating for healthier dietary choices. These dietary change efforts focused on lowering saturated fat from the traditional intake of high-fat milk products and butter and replacing these foods with low-fat and nonfat milk options, limiting added fat sources, and increasing consumption of fruits and vegetables. To strengthen the outcome measures, the population survey data was paired with blood samples. Then this information was compared to mortality statistics, hospital discharge data, and drug use. These community-based interventions worked. The decline in saturated fat was determined to be the main explanatory factor for the 20% decline in serum cholesterol on a population level and by extension a significant reduction in Finland’s coronary heart disease and mortality.
PURE Healthy Diet Score Study
The Prospective Urban Rural Epidemiology (PURE) study began in 2003 as an ongoing large-scale epidemiological study in 21 countries. Recently researchers used this database to create a healthy diet score like the Mediterranean, Dietary Approaches to Stop Hypertension (DASH), and Healthy Eating Index (HEI) diet scores. Translating the PURE Healthy Diet score into an eating pattern, the recommendations include plentiful servings of fruits, vegetables, legumes, nuts, and whole-fat dairy. Whole-fat dairy? This recommendation is a glaring difference from the other well-validated eating scores which advocate for the intake of low-fat dairy products.
It’s important to remember the limitations of the PURE study design which relies on self-reported data, and in turn, runs the risk of recall bias and cultural variations that make comparisons challenging. Additionally, reviewers cite concerns over the data collection methodology. Finally, the observational nature of the study design limited its ability to establish a cause-and-effect relationship.
Shifting to whole-fat dairy defies a body of evidence that is contrary to healthy eating patterns and other diet score indices. The fact that the type of fat found in dairy is saturated and saturated fat elevates LDL cholesterol, a logical and protective choice would be to continue recommending a healthy eating pattern that includes moderate amounts of dairy from low-fat and fat-free sources. These efforts bore fruit in the national improvement in Finland’s cardiovascular disease and mortality.
Ernest Hemingway's closing statement, "Isn't it pretty to think so," expresses a desire for what we’d like to be true. Yet on some rational level, we realize that flashy headlines like “Whole Milk and Cheese is Good for Your Heart” ring false. When it comes to saturated fat, time and time again, well-controlled, not merely observational data have shown a clear and consistent link with cardiovascular disease.