Cholesterol and saturated fat have long been thought to be related to the higher risk of heart disease seen in those eating more red meat. New research suggests that carnitine and choline may play a role. Carnitine is made from lysine, an amino acid. Red meat is an especially good source of carnitine, as are energy drinks and supplements. Most people make enough choline and do not need to have a dietary source. Apparently, bacteria that live in the intestines of humans digest dietary carnitine and turn it into another substance, TMAO, which can lead to blocked arteries. When vegetarians or vegans are given carnitine, they produce less TMAO than meat eaters, suggesting that vegetarians and vegans have fewer bacteria in their intestines that can convert carnitine to TMAO. This could help to explain why heart disease rates are lower in vegetarians.
As an aside, media reports of this study said that 77 vegetarians and vegans were fed red meat. The published study actually said that one long-term (>5 years) vegan male agreed to eat an 8-ounce sirloin steak and that a small group of vegetarians and vegans was given carnitine supplements but was not given meat. This shows how information gets distorted; if a story sounds off, it's necessary to read the original study.
Choline, an essential nutrient, may also be associated with increased risk of heart disease. Choline is also involved in TMAO production. Researchers fed 40 healthy adults two hard-boiled eggs. Eggs are high in choline. Blood TMAO levels of study subjects increased after they ate the eggs. These researchers also examined more than 4,000 adults and found that those whose blood levels were highest in TMAO were at highest risk of having a heart attack or stroke or of dying from heart disease. These results are preliminary but could help to explain the lower risk of heart disease seen in vegetarians.
Do you follow a vegetarian or vegan diet? If so, does reduced risk of heart disease play a role? Let us know in the comments.