This is a story that starts with some negative publicity for meat, fish, and eggs, but has a better ending, although much controversy remains and science is still working out pathways. Fortunately for us, all sides agree that wine and high-quality olive oil, as well as other high polyphenol foods, emerge as “fixers” of this newly discovered risk factor.
In 2013 there was renewed interest in the compound TMAO (trimethylamine N-oxide), which our bodies (specifically our gut bacteria and liver) make from dietary choline, carnitine, and lecithin. Those primary ingredients are enriched in meat, fish, and eggs in particular. Fish contain the highest amount of preformed TMAO of any food group. Several papers found associations between higher plasma levels of TMAO and increased risk for cardiovascular disease (heart attack or stroke) between 2013 and 2019. The papers caused a small panic in the paleo and carnivore camps, which had been advocating avoidance of grains, beans, and fruit due to the potential inflammatory effects of lectins, sugars, and processing. Also, it was difficult to square this new TMAO effect (risk) with the consistent and strong protective effects of frequent fish consumption. Other studies were published that did not always confirm the connection. The dietary ingredients (or sometimes they were given as supplements) were carnitine, choline, and lecithin. They were converted by the microbes to TMA and then by the liver to TMAO.