I Grew-Up in the era of Cholesterol-fear

I asked:

Was there ever any good evidence that dietary cholesterol had much to do with high serum cholesterol, or was it just confounded by dietary fat intake, where many fats contained cholesterol?

ChatGPT said:

The idea that dietary cholesterol significantly raises blood (serum) cholesterol was largely based on weak or confounded evidence. Over time, research has shown that the relationship is much more complex, and dietary cholesterol has far less impact on blood cholesterol than once believed.

Early Evidence: A Flawed Foundation?

1. Animal Studies (1910s–1940s)

   • 1913: Russian scientist Nikolai Anichkov fed rabbits high-cholesterol diets, leading to plaque buildup in arteries.
   • Problem? Rabbits are herbivores, and their bodies don’t process cholesterol like humans. This study did not translate well to human health.

2. Ancel Keys’ Research (1950s–1960s)

   • Keys' Seven Countries Study linked dietary fat (especially saturated fat) to heart disease, but dietary cholesterol was not the main focus.
   • However, public health advice bundled dietary cholesterol and saturated fat together, leading to confusion.

3. Framingham Heart Study (1948–Present)

   • Found a strong link between high serum cholesterol and heart disease, but no clear connection between dietary cholesterol intake and serum cholesterol levels in most people.
   • Framingham director William Castelli later admitted:
     “In Framingham, Massachusetts, the more cholesterol one ate, the lower the person's serum cholesterol.”

What Later Research Found (1970s–2000s)

1. Dietary Cholesterol Has Minimal Impact on Serum Cholesterol

   • Most people experience little or no increase in blood cholesterol from dietary cholesterol.
   • The body regulates cholesterol: when you eat more, the liver produces less; when you eat less, the liver makes more.
   • About 75% of blood cholesterol is made by the liver, not absorbed from food.

2. Saturated Fat, Not Dietary Cholesterol, Is the Bigger Factor

   • Studies found saturated and trans fats raise LDL (“bad” cholesterol) much more than dietary cholesterol.
   • Foods high in both cholesterol and saturated fat (e.g., red meat, butter) confused early researchers.

3. Eggs Were Unfairly Demonized

   • Eggs are high in cholesterol but don’t significantly impact blood cholesterol for most people.
   • Later studies found no strong link between egg consumption and heart disease, leading to revised guidelines.

Policy Reversals: Dietary Guidelines Catch Up

• 2015 U.S. Dietary Guidelines removed the cholesterol limit, stating:
  “Cholesterol is not considered a nutrient of concern for overconsumption.”
• The American Heart Association and Harvard now acknowledge that for most people, dietary cholesterol has little effect on blood cholesterol.

Final Verdict?

• Early concerns about dietary cholesterol were overblown and confounded by saturated fat intake.
• Dietary cholesterol has little effect on serum cholesterol for most people.
• Saturated fats and trans fats are much bigger contributors to high blood cholesterol.

So, the cholesterol scare was largely misplaced, and the public was misled for decades.