For more than half a century, Americans have been urged to shy away from saturated fats, found mainly in animal products. We have been told to cook with canola oil instead of butter, select skim instead of whole milk, and to fill our plates with pasta instead of steak.
Paradoxically, decades of adherence to this advice has coincided with rising levels of chronic disease. As people cut more saturated fat from their diets, the nation grew heavier and sicker — not healthier.
Put plainly, the war on saturated fat, rooted in the hypothesis that it causes heart disease, has never been based on sound science. In fact, a large and growing body of evidence reveals that saturated fats aren’t a menace but a key part of a healthy diet. And they should be recognized as such in national nutrition policy.
Fortunately, this long-overdue change now appears likely to happen next month. The federal government will soon release the new Dietary Guidelines for Americans — the nutritional blueprint that shapes everything from school lunches to hospital meals. Officials have finally signaled that they will lift the decades-old limit on saturated fat. This would mark a critical turning point.
The misguided crusade against fat began in the 1950s, when researcher Ancel Keys proposed a connection between saturated fat and heart disease. But in his seminal Seven Countries Study on the subject, Keys cherry-picked the countries that supported his claim and ignored others — like France and Germany — where people consumed plenty of butter and meat yet had low rates of heart disease.
In subsequent decades, scientists set out to test Keys’ hypothesis. They conducted a series of large randomized, controlled clinical trials around the world — some funded by the National Institutes of Health — enrolling a total of 67,000 participants. Subjects on experimental diets replaced animal fats with vegetable oils made from corn and soy, while the control groups ate the traditional diets of the time — with up to 18 percent of calories from saturated fat.
When the results of these “core trials” failed to confirm Keys’ hypothesis, researchers largely ignored or buried them. One major study went unpublished for 16 years. Scientists who later recovered and reanalyzed data from this study found, surprisingly, that the more the men lowered their cholesterol on a diet reduced in saturated fat, the more likely they were to die from heart disease.
Among dozens of review papers on the core trials, not one could point to evidence that lowering saturated fat had an effect on cardiovascular mortality or total mortality.
It is true that saturated fat increases LDL, the so-called “bad cholesterol” associated with heart disease. Participants in the core trials on the experimental vegetable oil diet did successfully lower their cholesterol. Even so, their mortality didn’t budge, and there was little to no effect on cardiovascular events.
One plausible explanation is that saturated fat also raises HDL — the “good cholesterol” that protects the heart — possibly equalizing the overall effect on heart disease risk. Another is that saturated fats only raise the type of LDL particle — called “large and buoyant” — that isn’t associated with cardiovascular disease.
Saturated fats may even have beneficial effects. The world’s largest observational study, following 135,000 people, found that those who ate more saturated fat suffered fewer strokes. Yet despite the substantial body of evidence, federal nutrition policy remains stuck in the past.
When the Departments of Agriculture and Health and Human Services issued the first Dietary Guidelines in 1980, 15 percent of adults were obese. Forty-five years later, 40 percent of American adults are now obese, three-in-four live with at least one major chronic disease, and one-third have prediabetes. Heart disease remains the nation’s leading killer.
We got here by replacing the whole, unprocessed foods that our ancestors ate for millennia with processed, refined carbohydrates — foods strongly linked to obesity, diabetes, and premature death.
The federal limits on fat are long overdue for correction. The guidelines have long told Americans to keep calories from saturated fat below 10 percent of total caloric intake and to swap butter for vegetable oil, full-fat dairy for low-fat.
There is no solid evidence that these swaps will improve health — as at least some experts behind our federal nutrition policy appear to have known. Internal communications from the Dietary Guidelines Advisory Committee in 2015 revealed the acknowledgment that there is “no data” to justify the 10 percent recommendation.
The scientific process may have been clouded by pervasive corporate ties among committee experts. Most of them, according to research published in a paper I co-authored for Public Health Nutrition last year, received funding from the ultra-processed food manufacturers that profit from keeping whole foods off the menu.
Thankfully, momentum is shifting. Policymakers in both parties are calling for a reexamination of the nation’s nutrition policies. FDA Commissioner Dr. Marty Makary has repeatedly said the demonization of saturated fat is “medical dogma” that must end.
Continuing to steer Americans away from butter, cheese, and meat ignores decades of evidence. As the next Dietary Guidelines take shape, policymakers have a rare opportunity to correct course and end the unfounded war on saturated fat.
Nina Teicholz is founder of the Nutrition Coalition and author of “The Big Fat Surprise” and a member of the Coalition for Metabolic Health.
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