To eat fat or not? If you find yourself not knowing how to choose your dairy in the grocery store, you are not alone. The confusion lies in part because the scientific literature constantly seems to be flipping back and forth, along with the infinite number of dietary fads and food industry advertising.
So, why is it that studies keep coming up with different results time after time?
It turns out that most studies of this kind are difficult to control and there can be multiple reasons why the results of one study differ from another. For example, dietary questionnaires may contain biases or may not accurately reflect what people are eating, or combine the types of fats that subjects consume, and still others may analyze the results with an eye toward a particular outcome (e.g. what do you want the results to say?). It’s also always important to see who is doing or sponsoring the study. Is it an advocacy group, a particular industry, or a university whose investigators have no outside links? All of these factors influence the study outcomes.
Dr. Steven Guyenet, a neurobiologist and biochemist, is on a quest to find the best strategies from the scientific literature to achieve good health, particularly when it comes to diabetes (1). He points to a new study (2) that identified a fatty acid (trans-palmitoleic acid) found exclusively in dairy fat and meat that reduces the risk of developing diabetes by 60%. Those with higher blood levels of this particular fatty acid were associated with healthier levels of blood cholesterol, inflammatory markers, insulin levels, and insulin sensitivity. He is careful to point out that this is an observational study and does not prove that dairy fat prevents diabetes.
In a comprehensive review of the literature (3,4), Guyenet also found that “high-fat dairy overall does not have a negative impact on obesity risk, metabolic problems, diabetes risk, or cardiovascular disease. In fact, these studies offer fairly strong support to the hypothesis that high-fat dairy may protect against obesity”… in particular grass-fed dairy. Again, he points out that these are observational studies and not a clinical trial.
So, can we say that saturated fats cause diabetes? Not quite. Nor do the papers suggest that we should necessarily increase our fat intake since our metabolism is not only affected by diet, but also by external factors such as exercise.
1. Dairy Fat and Diabetes.
2. Trans-palmitoleic acid, metabolic risk factors, and new-onset diabetes in U.S. adults: a cohort study.
3. The relationship between high fat dairy consumption and obesity, cardiovascular, and metabolic disease.
4. New Review Paper by Yours Truly: High-Fat Dairy, Obesity, Metabolic Health and Cardiovascular Disease.