Isn’t There Ironclad Scientific Evidence Damning Saturated Fat?
We have been told that saturated fat is unhealthy for so long by so many that most of us now just consider it common sense and would never think to question it. The presumption that dietary saturated fat causes heart disease (known as the “Diet-Heart Hypothesis”) is one of the fundamental tenements of major institutions like the American Heart Association, the National Heart, Lung, and Blood Institute, and The United States Department of Agriculture, so most would assume that their guidelines are based on sound scientific fact. But those who take the time to honestly evaluate the evidence will quickly see that no study has yet to show a solid causal link between consumption of saturated fat and the development of heart disease, cancer, diabetes, etc.
Nina Teicholz sums up the situation quite nicely in The Big Fat Surprise: Why Meat, Butter, and Cheese Belong in a Healthy Diet:
“…the disturbing story of nutrition science over the course of the last half-century looks something like this: scientists responding to the skyrocketing number of heart disease cases, which had gone from a mere handful in 1900 to being the leading cause of death by 1950, hypothesized that dietary fat, especially of the saturated kind (due to its effect on cholesterol), was to blame. This hypothesis became accepted as truth before it was properly tested, Public health bureaucracies adopted and enshrined this unproven dogma. The hypothesis became immortalized in the mammoth institutions of public health, And the normally self-correcting mechanism of science, which involves constantly challenging one’s own beliefs, was disabled. While good science should be ruled by skepticism and self-doubt, the field of nutrition has instead been shaped by passions verging on zealotry. And the whole system by which ideas are canonized as fact seems to have failed us.”
When it comes to the Diet-Heart Hypothesis, the phrase “passions verging on zealotry” belongs to one man above all others: Ancel Keys. His 1952 chart, “Fat Calories vs Deaths from Degenerative Heart Disease”, appears to show a nice and tidy upward curve connecting increased consumption of fat (shown along the X axis) and increased deaths per 1,000 from heart disease (going up the Y axis). But as many critical observers have pointed out, there are two big problems with this graph, and the theory it attempts to prove.
- The same curve could be plotted to show a correlation between deaths per 1,000 and per capita car ownership, cigarettes sales, protein consumption, and sugar consumption—essentially everything that came along with increases in wealth in the mid 20th century. Any one of these factors (or some combination of them) could be the cause of the increased rates of heart disease we’ve seen over the past 100 years. But we can’t be sure because Keys’ study can only tease out correlative relationships.
- Keys created the graph by cherry picking countries with data that fit his hypothesis. If one were to include a larger number data points, like Jacob Yerushalmy (the founder of the Biostatistics Department at the University of California, Berkeley) did in 1957 with 22 countries, a clean upward line can no longer be drawn and the correlation between dietary fat and heart disease evaporates.
But even if a correlation had remained after adding in more countries, we have to remember that at best, epidemiological (i.e. observational) studies like these can only show a possible correlation between saturated fat and disease.
By definition, such studies cannot prove causation. As every scientist knows (or rather, should know since many often seem to forget), correlation is not causation.
Okay, so observational studies cannot prove that dietary saturated fat causes heart disease. But what about controlled scientific trials? Bad news there, too, for the fat-phobic:
- The Women’s Health Initiative (WHI): 49,000 women were put on a low-fat diet in what would be the largest, longest trial ever conducted on the connection between fat consumption and disease. The results? Women did not lose weight as expected and saw no significant change in their risk for heart disease or cancer.
- The Framingham Heart Study: Though this study is often cited in support of the Diet-Heart Hypothesis, the study’s director actually made the conclusion (perhaps unintentionally) that eating fat made one more fit and active: “In Framingham the more saturated fat one ate, the more cholesterol one ate, the more calories one ate, the lower the person’s serum cholesterol… We found that the people who the most cholesterol, ate the most saturated fat, ate the most calories, weighed the least and were the most physically active.”
- The American MRFIT Study: Like the Framingham Heart Study, the MRFIT Study is also used frequently to support the Diet-Heart Hypothesis even though it showed some startling—albeit seldom reported—results. The study showed, for example, those who ate less animal fat and cholesterol actually had higher blood cholesterol.
Another great excerpt from Nina Teicholz’s The Big Fat Surprise sums up the Diet-Heart Hypothesis’ failure quite nicely:
“If, in recommending that Americans avoid meat, cheese, milk, cream, butter, eggs, and the rest, it turns out that nutrition experts made a mistake, it will have been a monumental one. Measured just by death and disease, and not including the millions of lives derailed by excess weight and obesity, it’s very possible that the course of nutrition advice over the past sixty years has taken an unparalleled toll on human history. It now appears that since 1961, the entire American population has, indeed, been subjected to a mass experiment, and the results have clearly been a failure. Every reliable indicator of good health is worsened by a low-fat diet. Whereas diets high in fat have been shown, again and again, in a large body of clinical trials, to lead to improved measures for heart disease, blood pressure, and diabetes, and are better for weight loss. Moreover, it’s clear that the original case against saturated fats was based on faulty evidence and has, over the last decade, fallen apart. Despite more than two billion dollars in public money spent trying to prove that lowering saturated fat will prevent heart attacks, the diet-heart hypothesis has not held up.”
Doesn’t Saturated Fat Cause Inflammation?
By now, most people have heard about “inflammation”, and most regard it as a bad thing. And it certainly is a bad thing if it’s chronic and systemic. But the body needs the ability to both inflame and anti-inflame to keep us healthy. It’s a matter of balance. If one were to eat only saturated fat day in and day out, then yes, they would indeed become imbalanced. But nobody ever eats all saturated fat even if one’s diet is comprised solely of bacon and eggs. All fats and oils are in fact a combination of different types of fatty acids. Many foods often wrongly maligned for their saturated fat content contain large amounts unsaturated fat, too. You may be surprised to learn that an egg yolk contains 70% unsaturated fatty acids: 47% oleic acid, 16% linoleic acid, 5% palmitoleic acid, and 2% linolenic acid. The remaining 30% is saturated fat: 23% palmitic acid, 4% stearic acid, and 1% myristic acid.
Avoiding saturated fat is not the goal. The focus should be on getting a variety of healthy fats from good sources (note again, however, that each of the following foods contain a variety of fats; they are simply listed by which kind of fat forms the majority):
- Saturated Fats: coconut oil, palm oil, grass-fed meat and dairy.
- Monounsaturated Fats: olive oil, avocados, avocado oil, lard, and poultry.
- Polyunsaturated Fats: wild caught fish, fish oils, and flaxseed.
Butter, Meat & Cheese Should Be Back on the Table
So to sum up, saturated fat does not cause heart disease. On the contrary, fat-rich foods are healthy, filling, and delicious, and deserve to be back on your table. Sufficient consumption of fat, including saturated fat, is critical for optimal health as Sally Fallon shares in her book Nourishing Traditions:
“Fats from animal and vegetable sources provide a concentrated source of energy in the diet; they also provide the building blocks for cell membranes and a variety of hormones and hormone-like substances. Fats as part of a meal slow down nutrient absorption so that we can go longer without feeling hungry. In addition, they act as carriers for important fat-soluble vitamins A, D, E, and K. Dietary fats are needed for the conversion of carotene to vitamin A, for mineral absorption and for a host of other processes.”