Saturated Fat: The Great Debate

Written by Marina Zhang on July 20, 2023. Posted in Current News

In this series, we will break down the actual health effects of vegetable oils and whether they’re a better alternative to saturated fats. Follow this series to find out whether what you’re using to cook with is really the best option

For more than half a century, central health authorities told the public to limit saturated fat intake as much as possible to prevent heart disease.

But a growing number of scientists and researchers have come to prominence challenging this narrative, arguing that saturated fat may not be that harmful and that limits on its intake shouldn’t be so stringent.

A Matter of Scientific Interpretation

Scientists from the two sides are looking at different studies on saturated fat and coming to different conclusions on its health effects.

The current dietary guidelines are based on the “diet-heart hypothesis,” which postulates that saturated fats are the leading culprits of cardiovascular disease.

The theory posits that when someone consumes food containing saturated fat, this fat increases LDL cholesterol (so-called bad cholesterol). This cholesterol accumulates in the blood vessels, forming atherosclerotic plaques that restrict and ultimately block blood flow, causing coronary heart disease.

However, this link between LDL cholesterol and heart disease has been challenged and so has the role of saturated fat in causing heart disease.

The Dietary Guidelines for Americans recommend limiting saturated fat to 10 percent or less of one’s daily calories, while the American Heart Association advises keeping saturated fat intake at 5 to 6 percent of one’s daily calories.

Evidence Supporting the Saturated Fat and Heart Disease Link

The argument in favor of limiting saturated fat intake is based on evidence that shows that replacing saturated fat with unsaturated fat decreases the risk of cardiovascular events. But usually, overall mortality rates don’t significantly improve.

The core studies showing this link were carried out in the 1960s and ’70s, forming the foundations against saturated fat intake.

These studies include the Los Angeles Veterans Administration diet study conducted in the 1960s. More than 800 men aged 55 or older participated in the trial. Half the participants replaced two-thirds of the animal fat in their diets with vegetable oil, while the other half continued to consume animal fat.

After six years, the first group saw a 13 percent drop in cholesterol levels, and only 48 men died from heart disease during the study compared with 70 in the group that consumed animal fat.

The caveat to this finding is that the overall mortality between the two groups was about the same, but more cancer cases were reported in the group that consumed vegetable oils.

Another highly cited study is the Anti-Coronary Club study conducted in the 1950s. The researchers didn’t intervene in the control group members’ diets, but the experimental group was told to reduce their animal fat intake, consume as much fish and poultry as they liked, consume one ounce of corn oil per day, and cook with polyunsaturated fat.

As a result of the intervention, participants’ cholesterol levels dropped and hypertension improved. However, more deaths were reported among this experimental group.

“The intervention studies were done in the ’60s and ’70s … and certainly the intervention studies suggested that there was a small benefit, but it wasn’t statistically very strong,” nutrition researcher Peter Clifton, who’s a professor at the University of South Australia, told The Epoch Times.

Mr. Clifton, who recommends replacing polyunsaturated fats with saturated fats, said more robust evidence supporting the diet-heart hypothesis comes from cohort studies that follow large populations.

One such cohort study published in 2015 examined more than 120,000 men and women. The researchers found that those who replaced 5 percent of their saturated fat intake with polyunsaturated fat and whole grains had fewer cardiovascular events.

Another 2014 cohort study published in Circulation followed more than 2,700 people and found that high levels of linoleic acid, an omega-6 fatty acid, in the blood were associated with fewer cardiovascular events.

A problem with cohort studies is that, unlike randomized controlled trials, they can’t prove causality.

Since researchers can’t control factors in participants’ lives, including dietary choices, any relationship is linked only by association. Cohort studies also take a long time, so participants may be lost during follow-up, which can introduce bias into the findings.

Evidence Against the Saturated Fat and Heart Disease Link

Scientists who challenge the current dietary recommendations to reduce saturated fat intake emphasize the limited evidence supporting such interventions.

They often cite the large randomized controlled trials that show that lowering saturated fat or replacing it with polyunsaturated fat had no effect or even caused harm.

Opposition to the link between saturated fat and heart disease includes the Sydney Diet Heart Study, the Minnesota Coronary Survey, and the Women’s Health Initiative Dietary Modification Trial.

In the 1990s, the Women’s Health Initiative Dietary Modification Trial involved nearly 49,000 postmenopausal women who had to reduce either their saturated fat intake to less than 10 percent or make no change in their diet.

The study found that reducing fat didn’t affect the women’s heart disease or weight loss.

The Sydney Diet Heart Study was conducted between 1966 and 1973. It put 458 men who had had a heart attack on a diet that replaced their saturated fat with soy oil. While the men’s LDL cholesterol dropped, their risk of death increased by more than 60 percent, and their risk of heart disease increased by 70 percent.

The Minnesota Coronary Survey, conducted at about the same time, followed 9,000 people and reported similar findings: LDL cholesterol levels fell while risks of death and cardiac events increased.

In 2020, 12 researchers came together to publish a state-of-the-art review in the Journal of the American College of Cardiology (JACC).

“Whole-fat dairy, unprocessed meat, and dark chocolate are SFA-rich [saturated fatty acid-rich] foods with a complex matrix that are not associated with increased risk of CVD [cardiovascular disease]. The totality of available evidence does not support further limiting the intake of such foods,” the authors wrote.

Regarding cohort studies, the perceived benefits of replacing saturated fats with polyunsaturated fats “could be attributed to a possible beneficial effect of polyunsaturated fatty acids and not necessarily to an adverse effect of SFAs,” according to the authors.

“The effect of saturated fat and raising LDL cholesterol is pretty small. So it’s not a really powerful fat,” Mr. Clifton said.

There are also large meta-analyses with findings that support both sides of the argument, such as the 2020 Cochrane Review.

Cochrane Reviews are recognized as the gold standard in research. The authors examined 15 randomized, controlled trial findings on replacing saturated fat with polyunsaturated and monounsaturated fat. The study concluded that this replacement reduced the risk of a cardiovascular event by 17 percent but didn’t affect overall mortality.

In his meta-analysis, Mr. Clifton used the study findings to support the dietary recommendation.

However, the same study was also cited in a 2021 commentary that called for more evidence.

The authors of this commentary emphasized findings that show that reducing saturated fats didn’t reduce total mortality, cardiovascular mortality, coronary heart disease mortality, fatal and nonfatal heart attacks, and coronary heart disease events.

Not All Saturated Fats Are Created Equal

Another argument put forward by the authors of the JACC report is that not all saturated fatty acids are equal, so health professionals should look at the sources rather than the overall consumption of saturated fat.

Lauric acid, a type of medium-length saturated fat commonly found in coconuts, strongly raises LDL cholesterol; therefore, some studies suggest that it elevates cardiovascular risk. However, studies on unrefined coconut oil suggest that it has an overall cardioprotective effect.

Butter is high in palmitic acid, another saturated fat with a potent LDL cholesterol-raising effect. However, a meta-analysis on butter has shown it to have a cardioprotective effect.

About 70 percent of dairy is saturated fat, yet studies have shown that high dairy consumption is heart-protective. Milk has short-chain saturated fat, which is linked to cardioprotective effects.

Beef has also been shown to have a relatively neutral effect on heart disease. Although beef is often associated with having high saturated fat, monounsaturated and polyunsaturated fats make up about 50 to 60 percent of beef fat.

Contrary to popular belief, the primary source of saturated fat may not be animal-based food but processed food, as argued by obesity researcher Zoe Harcombe, who holds a doctorate in public health nutrition.

The 2020–2025 Dietary Guidelines for Americans shows that processed food accounts for 42 percent of saturated fat consumed by Americans aged 1 year and older. On the other hand, animal-based food, including milk, meat, and poultry, makes up 27 percent (pdf).

Saturated fats are often added to processed food to prolong their shelf life and improve their texture.

Processed foods are also high in sugar, and professor Benjamin Bikman, a cell biology expert at Brigham Young University with a doctorate in bioenergetics, told The Epoch Times that the combination of saturated fat and refined carbohydrates is the most toxic.

Sugar in the blood oxidizes LDL cholesterol. This forms small, dense LDL cholesterol more prone to atherosclerosis. Sugar also increases triglyceride levels in the blood vessels. Oxidized LDL cholesterol and raised blood triglyceride levels are risk factors for heart disease.

To make things more complicated, research has shown that LDL cholesterol may not be the best predictor for cardiovascular risk.

See more here theepochtimes

Header image: Anna Hoychuk / Shutterstock

Please Donate Below To Support Our Ongoing Work To Defend The Scientific Method

PRINCIPIA SCIENTIFIC INTERNATIONAL, legally registered in the UK as a company incorporated for charitable purposes. Head Office: 27 Old Gloucester Street, London WC1N 3AX. 

Trackback from your site.