Eating more fruits and vegetables, and restricting meat, egg yolks and non-fermented dairy products, can help to reduce your chances of suffering a heart attack (J Amer Coll of Cardiol, 2020;75(7):763–72) and certain cancers (BMC Genomics, June 11, 2016;16(Suppl 7):S4). Eating just 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).

Why TMAO (TriMethylAmine Oxide) May Shorten Your Life
Meat, egg yolks and dairy contain large amounts of choline and lecithin, which pass to your colon. Your colon has more than 100 trillion bacteria, including some that are helpful and others are harmful. The harmful types include those that eat choline and lecithin and convert them into a chemical called TriMethylAmine (TMA). TMA is absorbed into your bloodstream and travels to your liver where it is converted to TriMethylAmine Oxide (TMAO). a chemical that has been shown to increase risk for heart attacks and certain cancers (Nutrients, Oct 1, 2018;10(10):1398; PLoS One, 2017;12:e0170742).

You need to have some choline and lecithin in your diet to have normal brain and nerve function, and low levels of these nutrients can interfere with your ability to learn and remember. Deficiencies of choline or lecithin can also damage your muscles and liver. However, you can get these nutrients in the small amounts you need from many plants such as wheat germ, beans, quinoa, brussels sprouts, broccoli, mushrooms, peanuts, cauliflower, peas, sunflower seeds, brown rice, tangerines, kiwifruit, carrots, apples, cabbage, kale, collard greens,bok choy, arugula, watercress and radishes.

Since so many plants contain choline and lecithin, you might think that eating these plants could harm you by increasing TMAO levels, but this does not happen. Cruciferous plants such as brussels sprouts are among the richest sources of choline in plants, but when researchers fed people two cups of brussels sprouts a day for three weeks, they found that TMAO levels went down significantly (Am J Clin Nutr, Jul 2011;94(1):240-6). Remember, not all colon bacteria convert choline to TMA, only the harmful colon bacteria. All vegetables discourage the growth of the harmful colon bacteria that make TMA from choline, so people who eat a lot of vegetables have fewer of the types of harmful bacteria that convert choline to TMA. This may explain why cruciferous vegetables are associated with a reduced risk of total deaths and deaths caused by heart attacks (J Amer Heart Assoc, Apr 2018;7(8):7:e008391).

Benefits of a High-Plant Diet
People who eat a plant-based diet have extremely low levels of TMAO and therefore are at lower risk for heart attacks (Int J Epidemiol, 2017 Jun 1;46(3):1029-1056). Even if vegetarians eat meat occasionally, they still have little or no rise in blood levels of TMAO because their plant-based diet encourages the growth in the colon of healthful bacteria and discourages the growth of colon bacteria that make TMA (Nat Med, 2013 May;19(5):576-85; J Clin Invest, 2019;129(1):373–387).

Meat, non-fermented dairy products and egg yolks increase blood levels of TMAO that:
• damages blood vessels to start plaques forming in your arteries
• causes 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)
• markedly increases clotting that can cause heart attacks and strokes (Cell, March 24, 2016;165(1):111–124)
• raises blood cholesterol levels by inhibiting reverse cholesterol transport and increases clotting by increasing platelet activation (Cell, 2016;165:111–124)
• damages DNA in your cells to increase cancer risk
• increases risk for colon cancer (Cancer Research, Oct 2014;74(24))
• increases growth of harmful Firmicutes colon bacteria that raise TMAO levels, and reduces levels of healthful Bacteroidetes that lower TMAO levels (Molecular Nutrition and Food Research, July 5, 2016)

Lowering TMAO to Help Prevent Heart Attacks
Restricting mammal meat and eggs markedly lowers blood levels of TMAO (Eur Heart J, Feb 14, 2019;40(7):583-594). The Mediterranean diet is high in olive oil and grapeseed oil, which contain a natural substance called DMB (3,3-dimethyl-1-butanol) that can 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 that were programmed to suffer a high rate of heart attacks, and it 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).

Trimethylaminuria
There is a genetic condition called trimethylaminuria in which people lack the liver enzymes necessary to break down the chemical trimethylamine (TMA) formed by the harmful colon bacteria. These people accumulate large amounts of trimethylamine (TMA) in their bloodstreams, which causes them to smell like rotten fish (“Fish Odor Syndrome”). When they stop eating meat, egg, and dairy foods and instead eat plenty of fruits and vegetables, their TMA levels drop and their fish odor disappears (Am J Med, Nov 2011;124(11):1058-63).

My Recommendations
Some people still think that eating meat, eggs or non-fermented dairy products every day is not harmful, even though many studies have shown strong associations with heart attacks and premature death. You do not need to be a vegetarian, but I recommend that everyone should at least limit the amounts they eat of these foods, and eat lots of plants. I think that the many studies we now have on TMAO should be convincing.
TMAO: Why Eating Meat or Eggs May Harm You
More Research on TMAO