Choline is found in a variety of foods including meat, eggs and milk. It's what's known as an essential nutrient, which means the body can't make enough choline on its own and so it must be provided in food.
But "unless prescribed by your doctor, avoid supplements with choline," said senior study researcher Dr Stanley L. Hazen of the Cleveland Clinic in Ohio, in a statement. Hazen and colleagues had previously shown that bacteria in the intestines interact with choline and other dietary nutrients to produce a substance called TMAO, and they linked high levels of TMAO in the blood to an increased risk of cardiovascular diseases. Also, in studies in animals, they linked higher levels of TMAO to a higher risk for blood clots.
Their latest research, reported in the American Heart Association's journal Circulation, shows that choline in food can affect blood clotting risk in humans, and in some cases, that risk can be minimized by taking low-dose aspirin. In the current study, they gave oral choline supplements to 18 volunteers and then measured TMAO levels, along with the responses of platelets, tiny particles involved in clotting.
After taking the supplements for up to two months, participants had more than 10-fold increases in blood levels of TMAO. The tendency of their platelets to clump together and form clots was also significantly increased, in direct proportion to the increases in TMAO levels.
Aspirin, which reduces the stickiness of platelets, reduced both the increases in TMAO and the increases in platelet clotting associated with choline, but it didn't completely eliminate them, the researchers found.