An essential nutrient available in meat and eggs could be responsible for an elevated risk of heart disease and stroke by upping the likelihood of blood clots, researchers at the Cleveland Clinic in Ohio uncovered.
The team, led by Dr. Stanley Hazen, was studying the link between meat consumption and heart disease and found this particular nutrient, called choline, may feed gut bacteria and create a by-product that makes blood sticky and prone to clotting.
It is this excessive blood clotting effect that later contributes to heart disease by limiting or blocking blood flow, and subsequently leading to myocardial infarctions and cerebrovascular accidents.
According to the American Heart Association, nearly 92.1 million American adults are currently suffering from some form of cardiovascular disease or the after-effects of stroke.
In its 2017 Heart Disease and Stroke Statistics Update, the association estimates more than 8 million adults will be living with heart failure by 2030.
What Is Choline And How Does It Influence Health?
Choline is a vitamin-like essential nutrient that, just like the vitamins in the B complex, plays an important role in brain development and keeping metabolism active.
Choline also regulates liver and nerve function, turns off the genes responsible for gaining visceral fat, and affects muscle movement, energy levels, and the process of eliminating LDL or "bad" cholesterol.
When choline is digested by the bacterial flora in the intestinal tract, it produces a compound called trimethylamine N-oxide (TMAO), which — as shown in the Cleveland Clinic study — causes the blood to clot excessively.
In an ironic turn of events, choline deficiency can also lead to heart disease, just like choline excess. The primary food sources that contain choline in abundance are egg yolks, liver, red meat, peanuts, and wheat germ.
A large egg delivers about 125 milligrams of choline, a little over a third of the recommended daily dose for women. For men, the adequate intake of choline from all dietary sources is 550 milligrams per day.
Choline is not the only nutrient that has TMAO as a by-product. Lecithin and carnitine also produce this type of oxide through bacterial digestion. All three nutrients are especially abundant in red meat, processed meats, and liver.
The role of gut bacteria in food digestion and metabolism has been amply documented in studies, which suggest that intestinal flora has a crucial impact on health. These bacteria offer protection against certain infections, influence obesity, may affect the risk of cancer and heart disease, and have even been linked to mental health.
What The Study On Choline's Blood Clotting Effect Found
To test their theory that choline raises the chances of blood clotting, the researchers devised an experiment that included 18 volunteers. Eight of the study participants were vegetarians or vegans, while 10 had an omnivorous diet (ate meat, eggs, and dairy).
In the experiment, the researchers administered the volunteers 500 milligrams of choline every day in the form of supplements. After a month, they observed that the subjects' TMAO blood levels increased by more than 10 times in both vegans/vegetarians and omnivores.
The same results occurred after two months of choline supplementation. Tests also showed the recipients' blood also became much more likely to form clots.
Hazen's team reported the vegan and vegetarian cohort had much lower levels of choline to start with and, even after taking the supplements, their TMAO levels were much lower.
"The new study provides the first direct evidence in humans that consuming excess choline, an essential nutrient plentiful in a Western diet, raises both levels of the bacteria-produced compound, called trimethylamine N-oxide (TMAO), and the tendency of platelets to clump together and form clots," said the AHA.
Another discovery made by the scientists was a low dose of aspirin - no more than 81 milligrams per day - reduced the incidence of clots. Although the aspirin didn't prevent TMAO levels from becoming elevated, it curbed their ability to promote clot formation.
"This is the first study in humans to directly demonstrate that dietary choline substantially elevates TMAO production by gut bacteria, impacting platelet function," said Hazen, who is chair of Cellular and Molecular Medicine, and section head of Preventive Cardiology and Rehabilitation at the Cleveland Clinic.
"Unless prescribed by your doctor, avoid supplements with choline," the scientist stated in the news release, adding that a Mediterranean diet or a vegetarian regimen were "reported to help reduce TMAO."
The team detailed their findings in a paper featured April 24 in the journal Circulation, a publication of the AHA.