The belief that saturated fat causes bad health outcomes is widespread and long held. This belief is especially prevalent regarding heart disease, and it has often been used to promote or defend vegan and vegetarian diets because saturated fat is found in greater proportions in animal-based foods. Unfortunately, it is a weak defense.

This view of saturated fat became prominent in the 1950s and 60s.^{[1][2][3][4][5]} When researchers compared the health value of diets in the Mediterranean area with diets more commonly seen in the US, one of the most consistent findings was that diets higher in saturated fat were highly correlated with higher rates of heart disease and certain cancers. In contrast, polyunsaturated fats (PUFAs), found in higher proportions in plants, were inversely associated with those diseases. Consequently, PUFAs have been considered healthier than saturated fat.

So the narrative went: Down with the saturated fat-laden butter and lard, up with plant oils! I remember this phase in the marketplace very well. However, there was a practical problem with plant oils. People wanted fats that were solid at room temperature because they wanted to be able to spread it on their bread like butter. To solve that challenge, a chemical process was devised to bubble hydrogen through the unsaturated oil to make it solid at room temperature. Unfortunately, this process led to a mostly synthetic fat known as trans fat. You likely already know what happened next: Evidence emerged to show that this unnatural form of fat causes heart problems, and trans fats have been avoided by many health-conscious consumers since.^[6][7]

Back to saturated fat, though, I believe that the high correlation between saturated fat-laden diets and heart disease is a classic case of correlation not necessarily equaling causation. It is, in my view, a misinterpretation of the research. Saturated fat as a cause of heart disease is not biologically plausible, and this relationship should have been questioned decades ago.

For one thing, saturated fat is relatively inert. I’ve written about this elsewhere: “If anything, unsaturated fat is far more likely to be the culprit in disease formation. Unsaturated fat is more biologically active, contributes to the formation of highly reactive oxygen species that promote diseases like cancer and heart disease, and promotes cancer more than saturated fat in experimental animal studies.”^[8] That’s right—plant oils experimentally promote cancer much more than saturated fats do.^{[9] [10]}This experimental observation is several decades old.

Does that mean we should consume saturated fats without concern? Not so fast. Excess saturated fat in the diet remains an excellent indicator of an unhealthy dietary pattern. Regardless of whether saturated fat is itself the cause of disease, the presence of foods high in saturated fat (mostly animal-based foods) remains a major concern.

Dietary saturated fat (and its companions, dietary cholesterol and total fat) is highly correlated with animal protein-based diets. And unlike saturated fat, animal protein is not biologically inert. For example, animal protein increases free radical oxidation, alters hormone activities, and creates metabolic acidosis.^{[11][12][13][14]} For over a century, compelling evidence has shown that animal-based protein raises blood cholesterol and causes heart disease more than dietary cholesterol does.^{[15][16][17][18][19][20]} (Later evidence in animal and human studies showed that this protein effect refers only to animal-based protein, not plant-based protein.^[21][22][23]) But seriously, who would dare to question protein, the bastion of not only animal-based foods but also the Western diet?

I have been concerned with this topic since the 1970s. I can distill my experiences throughout that time and this article into three observations:

1. The focus on saturated fat detracts from the health problems caused by animal-based foods, which primarily owe their unhealthy properties to their protein content. Animal-based protein not only stimulates mechanisms that lead to diseases like cancer and heart disease but also depresses mechanisms designed to protect us from those diseases.^{[24][25][26][27][28][29][30][31]} Moreover, the increased consumption of animal-based foods results in the decreased consumption of whole plant-based foods proven to protect us from heart disease and cancer.
2. Recommendations focused on saturated fat are much easier to discredit. They also provoke unnecessary confusion. For instance, individuals favoring an omnivorous diet would point out that despite decades of removing saturated fat from foods—as in skimmed milk and other low-fat products—we have achieved little or no health improvements. In a cohort of nearly 90,000 women in the Harvard Nurses’ Health Study, moderate reductions in fat did not result in substantial disease reduction.^[32] A decrease in fat might even result in a slight increase in disease risk, perhaps as a result of a higher concentration of animal protein in the diet.
3. The false saturated fat premise leads many to choose plant oils as a healthier alternative. But as I have already alluded to, plant oils and related synthetic products are not truly healthy alternatives. They are nutrient-deficient but calorically replete food fragments. Their excessive contribution to total calorie intake effectively displaces the consumption of whole plant-based foods. (Whole plants with fat, such as nuts, seeds, and avocados, provide far more nutrition than their corresponding oils; learn more about the nutritional value of oils versus whole foods.)

As the common misunderstanding about saturated fat (and cholesterol) became almost like a biblical verse, I predicted it might someday return to haunt us. And so it has.

References

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4. Keys A. Coronary heart disease in seven countries. Circulation Suppl. 41, I1–I211 (1970).
5. Keys A. Coronary heart disease—the global picture. Atherosclerosis 22, 149–192 (1975).
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