You have more than 100 trillion bacteria in your colon, and some are healthful while others are harmful. The harmful types include those that eat choline and lecithin, two chemicals that are found in high concentrations in red meat and egg yolks. These colon bacteria convert choline and lecithin into a chemical called TriMethylAmine (TMA), which is absorbed into your bloodstream and travels to your liver where TMA is converted to TriMethylAmine Oxide (TMAO).

You may be able to help prevent arteriosclerosis, heart diseases (including heart attacks), diabetes, and chronic kidney disease by avoiding red meat, which can lower blood levels of TMAO by changing the types of bacteria in your intestines. Eating two servings of red meat or processed meat per week (not poultry or fish) is associated with increased risk for heart attacks and premature death (JAMA, Mar 19, 2019;321(11):1081–1095), and an increase in red meat consumption of a half serving or more per day is associated with a 10 percent higher death rate (BMJ, June 12, 2019;365:l2110).

TMAO from Meat and Eggs
Eating red meat or eggs increases blood levels of TMAO that:
• damages blood vessels to start plaques forming in your arteries,
• markedly increases clotting that causes heart attacks and strokes (Cell, March 24, 2016;165(1):111–124), and
• damages DNA in your cells to increase cancer risk.
People who eat meat regularly have high blood levels of TMAO and are at markedly increased risk for colon cancer (Cancer Research Oct. 2014;74(24)). A review of 17 clinical studies covering 26,167 subjects, followed for an average 4.3 years, found that high blood levels of TMAO are associated with an almost double increased risk for an early death (European Heart Journal, July 19, 2017;38(39):2948–2956). The chances for dying increased by 7.6 percent for each 10 micromoles/L increase in blood levels of TMAO.

Researchers fed 18 healthy adults (10 meat-eaters and eight vegetarians) 450 mg of choline/day (the amount in 2-3 eggs) for two months and found that this diet raised TMAO by more than 10 times and increased clotting that can cause heart attacks and strokes. Then they gave a baby aspirin (81 mg) with the choline pills and found that this reduced the rise in TMAO and clotting caused by choline (Circulation, April 25, 2017;135 (17):1671). Another study also showed that a diet high in choline markedly increases the growth of harmful Firmicutes colon bacteria that raise TMAO levels, and reduces levels of healthful Bacteroidetes that lower TMAO (Molecular Nutrition and Food Research, July 5, 2016).

Lowering TMAO Helps to Prevent Heart Attacks
Having high blood levels of TMAO doubles your risk for heart attacks, strokes and premature death. The Mediterranean diet is high in olive oil and grapeseed oil, which contain a natural substance called DMB (3,3-dimethyl-1-butanol) that will kill the harmful firmicutes colon bacteria that make TMA, but not the healthful ones (Cell, 2015 Dec 17;163(7):1585-950). Dr. Stanley Hazen of the Cleveland Clinic showed that he could prevent diet-induced heart disease in laboratory mice by changing the types of bacteria in their intestines (Nature, April 7, 2011;472(7341):57–63). He fed DMB to mice programmed to suffer a high rate of heart attacks which:
• reduced their harmful colon bacteria,
• lowered blood TMAO levels and
• markedly reduced the plaques that formed in their arteries (Nature Medicine, Sept 2018;24:1407–1417).
He got the same results when he fed DMB to humans (Cell, Dec 17, 2015;163(7):1585-95). Inserting the harmful firmicutes into the colons of mice markedly increased their chances of forming plaques in their arteries (J Biol Chem, Feb 27, 2015;290(9):5647-60).

My Recommendations
Some people still think that eating mammal meat every day does not increase risk for heart attacks or premature death, even though the association between eating meat and premature death appears to be established. I think that the number of studies we now have on TMAO should be convincing. See my earlier reports: More Research on TMAO and Research on TMAO