Saturated Fat Reconsidered: New Research Challenges Old Dogma

Have you ever heard the saying “you can’t teach an old dog new tricks”? It’s not true. Many old dogs learn new tricks with the right training and motivation. It turns out that it could be a lot harder to teach old docs new tricks, especially when it comes to nutrition. Even though medical schools taught very little nutrition science decades ago, some physicians just can’t let go of the lessons they learned. One of them was to cut back on fat in the diet, especially saturated fat. New research doesn’t really support that approach. Will nutritionists and doctors change their advice?

What Did Doctors Learn About Nutrition?

During the middle of the 20th century, medical students were told that fat in general and saturated fat in particular raised cholesterol levels. It was seen as the driving force behind clogged arteries leading to heart attacks. Patients were urged to switch to margarine instead of butter, cut back on eggs and cheese and forego ice cream and burgers. After all, the thinking went, these foods are high in cholesterol and cholesterol is found in plaque in arteries.

Dietitians often recommended a “heart-healthy” breakfast of cornflakes with skim milk, toast with margarine and a glass of orange juice. Another option might be pancakes cooked on a nonstick griddle. The general advice was to stay away from any food with sat fat, especially dairy products such as cheese, butter, whole milk or ice cream. If people avoided saturated fat, they were told, they could reduce their risk of heart disease.

Margarine vs. Butter:

Before the century closed, nutrition science had found that margarine with its trans fats was actually causing more harm than butter. But health professionals have been reluctant to give up on fat as a dietary demon. That might be why low-fat products like skim milk and non-fat yogurt dominate the dairy case in most groceries. The American Heart Association still advises patients to limit saturated fat and select skim and low-fat dairy products.

Will Eating Saturated Fat Harm Your Health?

As you will read below, the evidence has been accumulating that saturated fat may not be the dietary demon it was once thought to be. A recent analysis from Japan concluded that reducing saturated fat intake is not effective for preventing heart disease (JMA Journal, March 21, 2025).

A new meta-analysis of 17 trials revealed that for most people, eating foods like butter and cheese or avoiding them makes no difference (Annals of Internal Medicine, Dec. 16, 2025). For people at low risk of cardiovascular problems, any benefit was below the level of importance. For people at high risk, however, the story is different. Replacing saturated fat with polyunsaturated fat, such as that found in many vegetable oils, was associated with 12 fewer heart attacks per 1,000 people over five years. In addition, 6 fewer people per thousand died during the five years analyzed. Thus, the answer to the question above really depends quite a bit on your baseline risk.

In an editorial published in the same issue, cardiologist Dr. Ramon Estruch and pharmacist Dr. Rosa Lamuela-Raventós wrote:

“Evidence indicates that medium-chain SFAs may improve lipid profiles, enhance glucose homeostasis, and aid weight management by increasing high-density lipoprotein cholesterol without significantly increasing low-density lipoprotein [LDL] cholesterol. Key sources include coconut oil, palm kernel oil, and dairy products.”

No doubt this will upset many people, but it is not the first hint that avoiding saturated fat is the key to cardiovascular salvation. Keep reading for our report on earlier studies that reached similar conclusions. Do keep in mind, too, that if you are at high risk because of heart disease or serious hypertension, you may get some benefit from moderating or reducing the saturated fat in your diet.

Dr. Estruch quoted above was one of the leaders of the PREDIMED study that uncovered the benefits of a Mediterranean-style diet. At first, doctors were surprised that people eating lots of extra-virgin olive oil or a handful of nuts daily had fewer cardiovascular problems than those encouraged to follow a prudent low-fat diet recommended by the American Heart Association. Since then, though, other data has supported the idea that avoiding fat is not essential for heart health in most cases.

EPIC Research Has Us Rethinking Heart-Healthy Nutrition:

A report suggests that some foods rich in sat fat are indeed risky, while others are not (Journal of the American Heart Association, Nov. 19, 2021). The scientists analyzed data collected as part of a large epidemiological study of diet and health in Europe. (For the epidemiologists out there, it’s the EPIC study–European Prospective Investigation into Cancer and Nutrition.)

During the study, more than 10,000 participants in ten countries had heart attacks, strokes or other cardiovascular events. Investigators matched their records to those of 16,000 volunteers who remained healthy. All of the people in this study filled out detailed questionnaires on diet and lifestyle.

Overall, there was no link between saturated fat consumption and risk of cardiovascular disease. However, there were differences based on foods. People who ate more red meat and butter were more prone to heart disease. Those who ate more yogurt, cheese or fatty fish, on the other hand, had a lower risk. The researchers noted this specifically because these foods are also high in sat fat.

This research, published in the Journal of the American Heart Association, challenges decades of advice to avoid all saturated fat. However, previous studies had also been undermining that blanket recommendation.

Data from a PURE Nutrition Study:

The definition of healthy eating has been shifting, based on actual data. Recent research called the Prospective Urban Rural Epidemiology (PURE) study carefully collected dietary information from 135,000 people (Dehghan et al, The Lancet, online Aug. 29, 2017).  After seven years, almost 6,000 people had died, and more than 4,700 had suffered heart attacks or strokes.

High-Carb Diets Were More Dangerous:

Analysis showed that the people who had been eating a high-carbohydrate diet were more likely to end up among the deceased or diseased. Those whose diets were richer in fat were less likely to have died. One particular correlation stands out: those consuming more saturated fat were at lower risk for strokes.

Previous Studies on Saturated Fat:

This is not the first study to suggest that saturated fat is not our enemy. The Minnesota Coronary Experiment ran from 1968 till 1973. In this randomized controlled trial, 9,000 patients were served meals high in saturated fat or unsaturated vegetable oil. The corn oil lowered cholesterol but did not improve survival. If anything, those eating corn oil were somewhat more likely to die (Ramsden et al, BMJ, April 13, 2016).

Another classic trial had similar results. The Sydney Heart Study randomized 458 Australian heart attack survivors to continue on their usual 1960s diet high in saturated fat or to substitute safflower oil for sat fat. The data were not published at the time, but the men on the low sat fat diet were more likely to have heart attacks and die (Ramsden et al, BMJ, Feb. 5, 2013).

Ten years ago, scientists published data throwing doubt on the danger of saturated fat. A meta-analysis indicated that the dietary advice in the 1977 US guidelines to cut fat intake, especially saturated fat, was not supported by the findings from randomized controlled trials that were available at that time (Open Heart, online Feb. 9, 2015).

This led the authors to remark that:

“It seems incomprehensible that dietary advice was introduced for 220 million Americans and 56 million UK citizens, given the contrary results from a small number of unhealthy men.”

Saturated fat has remained the main dietary villain for heart disease for over 60 years. Back in 2014, a meta-analysis of 72 studies with more than 600,000 participants determined that there was no association between how much saturated fat people ate and their risk of having a fatal or nonfatal heart attack (Annals of Internal Medicine, March 18, 2014). Another study published in the Journal of Nutrition (Feb. 2015) spent almost five years following over 2,000 people with diagnosed heart disease. The volunteers filled out detailed questionnaires about their dietary habits at the beginning of the study.

The conclusions were:

“There was no association between dietary intake of SFAs [saturated fatty acids] and incident coronary events or mortality in patients with established CAD [coronary artery disease].”

Such studies than made headlines because they challenged traditional medical advice. One might expect that health policy would change based on the latest scientific evidence. As we have seen, however, studies questioning the hypothesis that sat fat leads to heart disease can still make headlines.

Rethinking Nutrition Dogma on Saturated Fat:

Years of such studies have led investigators to question the diet-heart hypothesis so esteemed in nutrition circles. As new data (as well as new analysis of old data) demonstrate that old dietary beliefs were mistaken, health professionals need to rethink their advice. (Indeed, a few have begun to do so.) Sugar and other highly processed carbohydrates appear to be more hazardous to health than fat. Moreover, new studies point to problems with polyunsaturated fat sources such as soybean oil.

Learn More:

We have spoken with several physicians who have become convinced that we need to worry more about refined carbohydrates and sugar in our diets than about minimally processed fat. You can listen to our interviews with Dr. Robert Lustig, author of Fat Chance; Dr. Jacob Teitelbaum, author of The Complete Guide to Beating Sugar Addiction; and Dr. David Ludwig, author of Always Hungry. Our most recent interview with Dr. Ludwig is Show 1279: Challenging Dietary Dogma on Weight Gain.  For more from Dr. Lustig, listen to Show 1257: The Metabolical Results of the American Diet. You can also hear his thoughts in Show 1362: The Lowdown on New Medicines for Treating Obesity.