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Increased Heart Risk


Although a direct link to heart attack has not been made, intake of choline might raise blood levels of the compound TMAO, which has been linked with adverse health effects. However, the form of choline seems to matter, with greatest risk of elevated TMAO levels seen for free choline (i.e., choline bitartrate) and low to no risk found with forms of choline such as phosphatidylcholine or lecithin.

TMAO is produced from choline by the actions of microbes in the gut, turning choline into TMA, which is then absorbed and is converted by enzymes in the liver into TMAO. Higher blood plasma levels of TMAO have been linked with increased risk of heart attack and other major adverse cardiovascular events. TMAO can reduce normal cholesterol clearance and advance atherosclerosis (hardening of the arteries).

Free choline such as in choline bitartrate supplements may raise TMAO more than other forms because it is not well absorbed in the gut, so more is left to be digested by microbes and eventually converted to TMAO. Choline bitartrate has been shown to increase TMAO levels in clinical studies.

On the other hand, supplementing with phosphatidylcholine (another form of choline and a major component of lecithin) or eating foods high in phosphatidylcholine (such as liver, beef and pork) does not appear to significantly raise TMAO levels in the blood or urine. Similarly, eating one to two eggs (a dietary source of lecithin, yielding about 250 mg of choline mainly as phosphatidylcholine) per day can temporarily increase TMAO levels at one hour after intake, but levels appear to return to normal after about two hours and fasting levels (that is, levels at least 12 hours after eating) do not appear to be elevated. Nevertheless, routine consumption of these forms of choline should still be avoided, as these foods tend to be high in fat and cholesterol and have been linked with major adverse cardiovascular events and increased risk of death when consumed regularly in excess (such as more than one egg daily).

Less is known about the link between citicoline and TMAO, but it has been theorized that citicoline may be less likely to raise TMAO levels compared to free choline.

Following a Mediterranean, vegetarian or high-fiber diet can help reduce total choline intake.

Be aware that a similar connection with TMAO and cardiovascular disease risk has been made for L-carnitine from red meat and, possibly, from supplements with L-carnitine, including acetyl-L-carnitine — see the Concerns and Cautions section of the Acetyl-L-Carnitine Supplements Review for details.

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