TL;DR: In this episode of The Dr. Kumar Discovery Podcast, we revisit the origins of the diet-heart hypothesis and the studies that shaped nutrition policy for more than half a century. The question at the center is straightforward. If cholesterol is essential for every cell in the body, why would evolution design a molecule that suddenly becomes harmful in modern humans? This is the tension the episode unpacks. Click to listen.
Hi everyone,
For decades, the story about heart disease seemed settled.
Saturated fat raises cholesterol. High cholesterol causes heart attacks. Therefore, saturated fat must be the problem.
It was simple, persuasive and almost entirely built on assumptions.
The Problem: A Narrative That Outpaced the Evidence
Cardiovascular disease remains the leading cause of death worldwide. Urgent questions demand quick answers, and early researchers believed they had found a clear culprit when cholesterol appeared inside arterial plaque.
The conclusion seemed obvious. Cholesterol in arteries must come from the diet and must be the cause of disease.
Animal studies and observational data reinforced the fear, and by the time Ancel Keys published his Seven Countries Study, the public story was locked in. Saturated fat was dangerous. Low-fat diets were necessary. Margarine was healthier than butter. Seed oils were protective.
But the strongest clinical trials conducted at the same time did not confirm this narrative. They contradicted it.
Years later, Dr. Christopher Ramsden recovered long-buried data from two major randomized controlled trials: the Sydney Diet Heart Study and the Minnesota Coronary Experiment. These studies had one goal. Test whether replacing saturated fat with polyunsaturated seed oils reduced heart disease and saved lives.
They did not find the expected results.
Participants who replaced saturated fat with seed oils saw cholesterol levels fall, but deaths increased. In many older adults, removing saturated fat raised the risk of death. Autopsies showed no clear difference in arterial plaque between groups.
In other words, lowering cholesterol did not reliably prevent heart attacks, and the diet changes promoted for decades did not deliver the promised benefit.
For additional insights on cholesterol’s role and cardiovascular risk, see Does LDL-C Really Cause Heart Disease? A Critical Review of the Evidence .__
The findings were never widely publicized, partly because the momentum behind the original hypothesis was already too strong. Institutions, guidelines and cultural norms had been built on it.
The takeaway is not that cholesterol is irrelevant. It is that the biology is more complex than the simplified message that shaped the modern diet. Cholesterol is essential for hormone production, vitamin D synthesis and cell membrane integrity. The brain produces its own supply because it cannot risk falling short.
Learn more about why LDL cholesterol isn’t always the villain at LDL Cholesterol: Finding the Right Balance for Heart Health .
This episode invites listeners to examine the evidence more closely and understand why nutrition science is rarely as binary as it is presented to the public. Heart disease is not caused by a single molecule. It is shaped by metabolic health, inflammation, lifestyle and genetics.
Before accepting long-held assumptions about saturated fat or LDL cholesterol, listen to the evidence presented in this episode. It provides a clearer, fuller picture of cardiovascular science and the history behind our nutritional guidelines.
Explore the history, the science, and the data we were never shown.