A brilliant and very important breakthrough study shows that restricting mammal meat and eggs markedly lowers blood levels of TMAO (Eur Heart J, Feb 14, 2019;40(7):583-594). Mammal meat and eggs are rich sources of choline, carnitine and lecithin that are converted in your body to a chemical called TMAO that can damage arteries, which can cause plaques to form and later to break off to cause heart attacks and strokes. This is a very exciting article because it uses diets with the same total calories to show that mammal meat causes the highest rises in blood levels of TMAO in healthy adults and this very high rise in TMAO is completely independent of the amount of saturated fats in the diet.

The authors showed that mammal meat increases blood and urine TMAO levels an average of three times higher than the equivalent in chicken or vegetarian meals. There was no difference in TMAO blood levels between high and low saturated fat diets that had red meat as their protein source. Removing as much fat as possible from the meat did not produce TMAO levels lower than meat that had a lot of fat. Participants lowered their blood levels of TMAO by going from a diet based on mammal meat to one based on chicken. The authors also showed that carnitine caused higher blood levels of TMAO than lecithin. See my earlier reports: Research on TMAO
Why I STILL Restrict Meat, Eggs and Milk

How Foods High in Choline, Carnitine or Lecithin Increase Heart Attack Risk
When you eat foods rich in choline, carnitine and/or lecithin,
• these chemicals pass through your intestines,
• where bacteria there convert carnitine and lecithin to TMA, trimethylamine (PLoS One 2017;12:e0170742).
• TMA is absorbed into your bloodstream and is then
• converted by your liver into trimethylamine-N-oxide (TMAO), a substance that has been shown in many studies to cause plaques to form in arteries, which can break off from the arteries to increase risk for heart attacks (Am J Clin Nutr, 2016;104:173-80; N Engl J Med 2013;368:1575-84).

Further Studies
• Vegetarians and vegans had much lower blood TMAO levels than people who ate meat. Feeding carnitine pills to animals markedly increased plaques to form in arteries without any changes whatever in blood levels of HDL or LDL cholesterol, or sugar or insulin (Nat Med, 2013;19:576–585).
• A study of 80,978 women from the Nurses’ Health Study and 39,434 men from the Health Professionals Follow-Up Study found a much higher death rate in people who ate a high-choline diet full of mammal meat and eggs (Am J Clin Nutr, 2016;104:173-80). The authors did not measure blood levels of TMAO.
• TMAO raised blood cholesterol levels by inhibiting reverse cholesterol transport and increases clotting, the ultimate cause of heart attacks, by increasing platelet activation (Cell, 2016;165:111–124).

TMAO Blood Levels Can Predict Severity of Disease and Risk of Death
• In people showing up in an emergency room with chest pain, high blood levels of TMAO increase risk for death from heart disease within the next six months (Eur Heart J, 2017;38:814–824).
• In people who have stable coronary artery heart disease, high fasting blood TMAO levels predict increased risk for dying within five years (J Am Heart Assoc, 2016;5:e002816).

My Recommendations
I report on studies such as this one because I find them interesting and hope you will too. I realize that trying to follow the latest headlines on good and bad foods can be confusing and frustrating, and I do not recommend trying to analyze everything you eat. Once again, my definition of a healthful diet is one that is high in vegetables, unground whole grains, beans, fruits and nuts; and low in animal products, sugar-added foods, sugared drinks including fruit juices, fried foods, and refined carbohydrates such as bakery products, pasta and most dry breakfast cereals. Try to follow this pattern most of the time and adapt it to your special needs and preferences.

Checked 2/17/23