TMAO and Choline in Pregnancy
Questions have been raised about higher levels of a choline byproduct, trimethylamine oxide (TMAO). In older men with pre-existing heart disease, TMAO has been associated with more subsequent heart problems. Cardiac problem from TMAO were not found in studies of young adults. TMAO is made by certain bacteria feeding on undigested choline supplements that reach the large intestine. Phosphatidylcholine is more completely absorbed so that less reaches the large intestine. It is also impervious to the bacteria. Women who choose choline supplements for their lower cost and smaller tablets can make sure to divide their choline into three or four doses throughout the day and to take their choline with food and liquids, to prevent large amounts from reaching the bacteria in the large intestine. The fetus is not affected by TMAO, because very little crosses the placenta, and the fetus does not have intestinal bacteria. Lobster, squid, salmon, turbot, and other salt-water creatures have much higher amounts of TMAO than the amounts created by intestinal bacteria after consuming eggs, meat, or choline supplements. Fresh water fish and canned tuna are low in TMAO.
 
Read more: Effect of Choline Forms and Gut Microbiota Composition on Trimethylamine- N-Oxide Response in Healthy Men.
Circulating trimethylamine N-oxide levels following fish or seafood consumption.