Certain gut bacteria turn nutrients from meat, eggs, and dairy into a compound called TMAO. A growing body of cardiovascular research treats that compound as one of the more concrete links between gut health and heart disease.[1]
Roughly 36 bacterial species carry the genes needed to make TMA, the compound the liver later converts into TMAO.[1] Firmicutes bacteria such as Clostridium and Streptococcus, along with Proteobacteria like E. coli, do most of this work. Bacteroidetes species don't produce TMA at all, which is part of why individual gut composition affects how much TMAO a person's body generates from the same meal.
TMAO appears to drive this risk through several mechanisms at once. It encourages the formation of artery-clogging foam cells, worsens the blood vessel lining's function, increases how easily platelets clump together, and interferes with the body's own bile acid production.[1] Gut bacteria influence heart health through other pathways too, including short-chain fatty acids that lower blood pressure and inflammation, and vitamin K2 production that helps keep calcium out of artery walls. The same bacteria-organ relationship shows up elsewhere in the body too, including the lungs, as described in The gut-lung connection: what the research shows.
What to do with this
TMAO levels rise mainly in response to choline and carnitine intake, found concentrated in red meat, egg yolks, and certain dairy products. Red meat and eggs each raise TMAO through slightly different mechanisms, covered separately in Red meat and your gut: what TMAO research shows and Eggs and your gut: what TMAO means for your breakfast. A diet leaning more toward plants and fish tends to produce less of it. This isn't a reason to eliminate eggs or meat entirely, since the research is about degree and pattern rather than any single meal. If you have existing cardiovascular risk factors, ask your doctor whether TMAO testing is relevant to your case. Treat gut-supportive habits, fiber, plant diversity, less ultra-processed food, as one more lever alongside standard heart-health advice.
