Trimethylamine N-oxide (TMAO) is a metabolite formed when gut bacteria break down compounds such as choline and carnitine. The resulting trimethylamine (TMA) is absorbed into the bloodstream and converted into TMAO, mainly in the liver. Research suggests that elevated levels of TMAO in the blood may be associated with a higher risk of cardiovascular disease, chronic kidney disease and inflammation, although links with conditions such as diabetes and fatty liver disease are still being studied.
Foods containing choline and carnitine, particularly red meat, eggs and dairy products, can contribute to TMA production. Fish and seafood can also contribute to circulating TMAO because they may contain TMAO directly. Certain supplements containing carnitine or choline may also increase TMAO production.
A diet rich in fibre and plant-based foods, such as a Mediterranean-style diet, may help influence the gut microbiome and lower circulating TMAO levels. Limiting excessive consumption of red and processed meat and avoiding unnecessary carnitine supplements may also help. However, TMAO is still an area of active research, and lowering TMAO has not yet been established as a way to prevent cardiovascular or other diseases.
Trimethylamine N-oxide (TMAO) is a metabolite formed through the interaction between the gut microbiome and the body’s metabolism. Gut bacteria can break down dietary compounds such as choline and carnitine to produce trimethylamine (TMA). TMA is then absorbed into the bloodstream and transported to the liver, where it is converted into TMAO, primarily by an enzyme called flavin-containing monooxygenase 3 (FMO3). TMAO is subsequently removed from the body mainly through the kidneys.
There is growing evidence that higher levels of circulating TMAO may be associated with an increased risk of cardiovascular disease and chronic kidney disease. However, researchers are still investigating whether TMAO itself directly causes these conditions or whether it is partly a marker of other dietary, metabolic and kidney-related factors.
Choline and carnitine are essential nutrients that are found in a variety of foods. Eggs, meat, poultry and dairy products contain significant amounts of choline, while carnitine is particularly abundant in red meat and is also found in dairy products and other animal-derived foods.
A study conducted in 11,768 participants tracked the relationship between circulating TMAO and heart failure over a median follow-up period of almost 16 years. During this period, 2,102 cases of heart failure occurred. Researchers found that higher concentrations of TMAO were associated with an increased risk of developing heart failure, even after adjusting for traditional cardiovascular risk factors.
These findings suggest that TMAO may have potential as a biomarker of cardiovascular risk. However, TMAO is not currently established as a standalone screening test for heart failure, and further research is needed to determine whether directly lowering TMAO can reduce the risk of cardiovascular disease.
Dietary choices can influence TMAO levels through several pathways. Foods containing choline and carnitine can provide substrates for gut bacteria to produce TMA. In addition, some fish and seafood naturally contain TMAO.
Foods that may contribute to higher TMAO levels include:
It is important to remember that the presence of TMAO or its dietary precursors does not automatically make a food unhealthy. Overall dietary pattern, portion size and nutritional quality are important considerations.
Elevated circulating TMAO levels have been associated with an increased risk of several health conditions. However, researchers are still investigating whether TMAO directly contributes to these conditions or is a marker of underlying metabolic or dietary factors.
Higher circulating TMAO levels have been associated with an increased risk of cardiovascular disease, including atherosclerosis, heart attack and heart failure. Research is ongoing to determine the extent to which TMAO directly contributes to these conditions.
Higher TMAO levels have been associated with inflammatory processes in different organ systems. The mechanisms involved and the extent to which TMAO directly causes inflammation are still being studied.
Higher TMAO levels have been associated with hypertension in some studies. Researchers have proposed several possible mechanisms involving blood-vessel function and vascular inflammation, but the causal relationship remains under investigation.
TMAO is primarily eliminated from the body through the kidneys. People with chronic kidney disease often have higher circulating TMAO levels because reduced kidney function can impair its clearance. Changes in the gut microbiome associated with chronic kidney disease may also influence TMA production.
Patients with higher TMAO levels may be more likely to have insulin resistance and impaired glucose metabolism. However, research into the relationship between TMAO and type 2 diabetes is ongoing, and the underlying cause-and-effect relationship remains inconclusive.
Studies have reported associations between higher TMAO levels and metabolic dysfunction-associated steatotic liver disease (MASLD), formerly known as non-alcoholic fatty liver disease (NAFLD). However, the relationship between TMAO, fatty liver disease and liver fibrosis is still being investigated.
Dietary changes that support a healthy gut microbiome may help influence TMAO production and circulating TMAO levels. However, there is currently no established dietary treatment specifically aimed at lowering TMAO, and reducing TMAO has not yet been proven to prevent disease.
Following a Mediterranean-style or predominantly plant-based diet may help lower circulating TMAO levels. These dietary patterns are rich in vegetables, fruits, whole grains, legumes, nuts and seeds and are also associated with better overall cardiovascular health.
Red meat is a rich source of carnitine and can contribute to TMA production by gut bacteria. Limiting red and processed meat and replacing some of these foods with plant proteins such as lentils, beans, peas and other legumes may help reduce exposure to TMAO precursors while supporting a heart-healthy diet.
Eggs are an important source of several nutrients, including choline, and there is no need for most people to eliminate egg yolks solely to reduce TMAO. Overall dietary balance and individual health needs should guide egg consumption.
Eating more fibre supports a diverse and healthy gut microbiome. Fibre-rich foods such as vegetables, fruits, whole grains and legumes can influence the composition and activity of gut bacteria and may help reduce TMAO production. The relationship between dietary fibre, the gut microbiome and TMAO is complex and continues to be studied.
Some sports and bodybuilding supplements contain carnitine or choline and may increase the availability of these compounds for TMA production. Avoid taking high-dose or unnecessary supplements without discussing them with your doctor, particularly if you have cardiovascular or kidney disease.
TMAO is an emerging area of research at the intersection of nutrition, the gut microbiome, cardiovascular health and kidney function. While elevated circulating TMAO levels are associated with several chronic diseases, researchers are still determining whether TMAO is a cause of disease, a marker of disease risk, or both. For now, focusing on an overall balanced, fibre-rich and heart-healthy diet remains more important than trying to target TMAO alone.
TMAO (trimethylamine N-oxide) is a metabolite produced when gut bacteria break down nutrients such as choline and carnitine. Higher TMAO levels have been associated with cardiovascular and kidney disease, although research is still ongoing.
Foods containing choline and carnitine, such as red meat, eggs and dairy products, can contribute to TMAO production. Fish and seafood may also contain TMAO directly.
Higher circulating TMAO levels are associated with an increased risk of cardiovascular conditions, including heart disease and heart failure. However, researchers are still studying whether TMAO directly causes these conditions.
Eating more vegetables, fruits, whole grains, legumes, nuts and seeds may support a healthier gut
microbiome. Limiting excessive red and processed meat and avoiding unnecessary choline or carnitine supplements may also help.
Not necessarily. Eggs provide important nutrients, including choline, and most people do not need to eliminate egg yolks solely to reduce TMAO. Overall diet quality and individual health needs are more important.
Higher TMAO levels have been associated with chronic kidney disease and metabolic conditions such as insulin resistance and type 2 diabetes. However, the cause-and-effect relationship is still being investigated.
TMAO is currently an emerging biomarker rather than a standalone screening test for heart disease or heart failure. Your doctor can recommend established cardiovascular and metabolic tests based on your individual risk factors.
Kauvery Hospital is globally known for its multidisciplinary services at all its Centers of Excellence, and for its comprehensive, Avant-Grade technology, especially in diagnostics and remedial care in heart diseases, transplantation, vascular and neurosciences medicine. Located in the heart of Trichy (Tennur, Royal Road and Alexandria Road (Cantonment), Chennai (Alwarpet, Radial Road & Vadapalani), Hosur, Salem, Tirunelveli and Bengaluru, the hospital also renders adult and paediatric trauma care.
Chennai Alwarpet – 044 4000 6000 • Chennai Radial Road – 044 6111 6111 • Chennai Vadapalani – 044 4000 6000 • Trichy – Cantonment – 0431 4077777 • Trichy – Heartcity – 0431 4077777 • Trichy – Tennur – 0431 4022555 • Maa Kauvery Trichy – 0431 4077777 • Kauvery Cancer Institute, Trichy – 0431 4077777 • Hosur – 04344 272727 • Salem – 0427 2677777 • Tirunelveli – 0462 4006000 • Bengaluru – 080 6801 68011
