Choline is a B-complex vitamin found in the lecithin of many plants and animals. The Institute of Medicine notes that is prevents some chronic diseases. That's good. But a new paper suggests supplemental choline is clot enhancing. That's bad.
Which is it? Let's explore.
Weifei Zhu et al., report that a diet supplemented with choline  resulted in elevated levels of trimethylamine N-oxide (TMAO) which is associated with thrombotic events (blood clotting). They demonstrated in 18 patients, eight vegans/vegetarians, and ten omnivores that 1000 milligrams of supplemental choline resulted in elevated TMAO levels and an enhanced platelet aggregation response. The response seemed to be dose dependent and was mitigated to some extent by 81 milligrams of aspirin taken daily. They believe they demonstrated that dietary choline resulted in increased TMAOs and that aspirin reduced TMAO’s enhancement of platelet aggregation.
Based on one paper, the media claimed that “Gut bacteria may turn common nutrient into clot-enhancing compound” and “Choline, Common in Eggs and Liver, Raises TMAO Levels and Increases Platelet Aggregation.”
Don't take them to heart, so to speak. These results have not been replicated by others and they could simply be wrong.
The National Academies of Sciences, Engineering, and Medicine Health and Medicine Division (still called Institute of Medicine by a lot of people - or at least me) certainly disagrees. They note that choline is an essential nutrient and that we need about 500 milligrams daily . And their upper limit for intake is three times that provided by the supplement in this exploratory study. In another paper looking at choline, choline deficiency was stressed and they noted with respect to cardiovascular disease that choline deficiency resulted in elevated homocysteine and elevated homocysteine, in turn, was associated with “greater risk for several chronic diseases and conditions including cardiovascular disease, cancer, cognitive decline and bone fractures.” They concluded that
“There is an immediate need to increase awareness among health professionals and consumers of choline as an essential, but currently suboptimal, nutrient, and …that for the majority of the population choline consumption is far below current dietary recommendations. Increasing awareness of the pervasiveness of suboptimal choline intakes must become the focus of public health efforts in order to promote optimal health.”
So, who should you believe?
Too low a level and we risk cardiovascular disease, too high a level and we risk cardiovascular disease.
When we make decisions like this, we often rely on information that is immediately available to us (Availability heuristic), which may cause us to swing back and forth between too little and too much. Science consists of reproducible facts, but those can be both valid and contradictory, at least if we consider the results of one paper that was a pilot study. So this paper is not a milestone; it may be a small step forward and increase our knowledge of the known, or it could be wrong. Either way it does little to help us understand the unknown (mystery?) of how, what we eat, interacts with everything else in our lives and the environment.
Given the recent March for Science it is important to remember that Science is not a dogma, it is a model. A very successful model, but a model that is only an approximation of our world.
 Those of you with sci-hub can find it using this doi, 10.1161/CIRCULATIONAHA.116.025338
 Choline functions as a precursor for acetylcholine, phospholipids, and the methyl donor betaine.
 Requirements for women are slightly less and additionally vary with lactation and pregnancy.