Warnings against saturated fat on heart health need to be revisited as flaws were revealed in the seminal 1950s studies on which these warnings were based, according to new research coming out of the Ateneo de Manila University.
Outdated and unsupported research from the 1950s erroneously conflated the saturated fats found in meat and dairy with the harmful industrial trans-fats commonly used in margarine and shortening. PHOTO CREDIT: Felicity Tai / Pexels.com
In 1953, spurred by an apparent surge in heart disease in the US, physiologist Ancel Keys published a study that introduced the “lipid-heart hypothesis.” He claimed without evidence that high saturated fat and cholesterol in the diet raise cholesterol levels in the blood and contribute to heart disease. He developed what is now known as the Keys equation, where he sought to mathematically predict serum cholesterol levels based on saturated fat and cholesterol intake.
However, Ateneo de Manila University professor and chemist Dr. Fabian M. Dayrit, and American physician Dr. Mary T. Newport, have recently called into question the lipid-heart hypothesis and the Keys equation in their review paper entitled, “The Lipid-Heart Hypothesis and the Keys Equation Defined the Dietary Guidelines but Ignored the Impact of Trans-Fat and High Linoleic Acid Consumption.” The paper was recently cited for the special achievement of being viewed 4,931 times from the open-access journal Nutrients since its publication on May 11, 2024.
Newport and Dayrit pointed out that Keys erroneously conflated the saturated fats found in meat and dairy with the harmful industrial trans-fats commonly used in margarine and shortening. Keys also included coconut oil in the warning.
They argue that this misunderstanding has led to flawed dietary recommendations, including a disproportionate focus on heart disease at the expense of research into the role of trans-fats in cancer, obesity, and other metabolic disorders. These conditions have been steadily on the rise in the decades since Keys published his findings.
“Numerous observational, epidemiological, interventional, and autopsy studies have failed to validate the Keys equation and the lipid-heart hypothesis. Nevertheless, these have been the cornerstone of national and international dietary guidelines,” the researchers said in their paper.
The study highlights that trans-fats, commonly found in processed foods, are strongly linked to heart disease. These industrial fats were widely consumed during the twentieth century but ignored in dietary guidelines that were based on Keys’ claims.
It also critiques the unregulated promotion of polyunsaturated fats—specifically linoleic acid, commonly found in soybean oil and other vegetable oils—which can lead to an imbalance in omega-6 and omega-3 fatty acids and increase the risk of chronic inflammation and other health issues.
Dayrit and Newport argue that dietary guidelines based on Keys’ lipid-heart hypothesis are outdated and not supported by scientific evidence. They also underscore the need to distinguish between different types of fats and take a more nuanced approach to dietary recommendations.
