Choline is an essential nutrient that plays a role in the synthesis of phospholipid membranes and is a source of methyl groups that are needed for many steps in metabolism. It’s also the precursor to the neurotransmitter acetylcholine. Choline has particular relevance for brain development, liver health, and skeletal muscle function. Choline is mostly found in animal foods such as eggs, milk, fish, chicken, and beef, but some plant foods also contain choline.^[2]

Choline supplementation during pregnancy or early childhood has favorable effects on children’s brain function and neurodevelopment, including memory, attention, and visual-spatial learning.^[3] Choline supplementation among children with fetal alcohol spectrum disorder improves memory, nonverbal intelligence, visual-spatial skills, ADHD symptoms, executive function, and white matter microstructure.^[4][5][6] These effects occur primarily when choline is supplemented before the age of 5.

Higher choline intakes have been associated with a lower risk for cardiovascular events and stroke, cognitive impairment, post-stroke depression,^[7] cardiovascular disease,^[8] and dementia.^[9] A higher intake of choline is also associated with lower levels of cardiometabolic risk factors.^[10] Interestingly, a low choline intake may impair gains in strength and lean mass in response to exercise training^[11][12] and reduce cognitive function.^[9]

High/excessive intakes of choline can result in some side effects, including a fishy body odor, vomiting, excessive sweating and salivation, low blood pressure (hypotension), and liver toxicity.^[1] In addition, choline consumption has been shown to increase the production of trimethylamine N-oxide (TMAO), which is associated with an increased risk of cardiovascular disease. However, some studies indicate that the amount of choline consumed in 3 eggs per day does not elevate plasma TMAO levels.^{[13][14][15][16][17]} Some studies have associated higher choline intakes with increased atrial fibrillation risk^[18] and type 2 diabetes.^[19]

Dietary choline is a precursor for the neurotransmitter acetylcholine (ACh), which is crucial for normal cognitive and motor function. Choline is irreversibly oxidized into betaine in the liver and kidneys. Betaine is a methyl group donor that participates in the important process of remethylating homocysteine to methionine. Choline is also a precursor for the synthesis of phosphatidylcholine, the most abundant form of phospholipid in the body.^[2]

Choline is important for neural tube closure, stem cell proliferation, and apoptosis (programmed cell death) in the fetal brain during early pregnancy. The choline metabolite phosphatidylcholine is also required for packaging and exporting very-low-density lipoproteins from the liver and the secretion of bile acid salts; the disruption of this process can contribute to the accumulation of triglycerides in the liver.^{[20][21][22][23][24]}