The Impact of TMAO and Dietary Choices on Cardiovascular Health

TMAO Overview

Trimethylamine N-oxide (TMAO) is a metabolite formed by our gut bacteria. Essential nutrients like phosphatidylcholine (also known as lecithin), choline, and L-carnitine, predominantly found in foods from animal sources like red meat, egg yolks, and high-fat dairy, undergo digestion by these gut bacteria. This process leads to the release of certain metabolites, including TMA (trimethylamine), into our bloodstream. Once in the liver, TMA is transformed into TMAO. Research has demonstrated that TMAO plays a critical role in regulating various physiological processes that are linked to the onset of atherosclerosis, a condition characterized by the hardening of the arteries.

What foods are rich in dietary TMAO precursors?

Choline and Carnitine

While choline is an essential nutrient and we need it in our diet, it’s crucial to avoid excess intake from foods of animal origin. Interestingly, high-choline plant foods like Brussels sprouts may actually help reduce TMAO levels, as they seem to naturally downregulate the TMAO-producing liver enzyme. Moreover, individuals following a completely plant-based diet may not produce TMAO at all, even when consuming foods rich in choline and carnitine, due to the different microbial communities in their gut.

Cardiovascular Disease

Researchers are discovering more and more associations between TMAO levels and the development of multiple inflammatory conditions. TMAO has also been shown to directly cause atherosclerosis, the harmful buildup of plaque in your arteries. Having higher plasma TMAO levels predicts major adverse cardiovascular events, like heart attack, stroke, and death. And TMAO appears to promote immune and inflammatory responses in the body that facilitate atherosclerosis and other heart problems.

According to a study featured in the European Heart Journal, researchers monitored TMAO levels for 530 participants and tracked the number of cardiac events. The findings revealed that individuals with higher TMAO levels faced an increased risk of having fatal heart attacks or strokes.

In a 2020 meta-analysis published in BMC Cardiovascular Disorders, researchers examined data from seven papers, with data from nine cohort studies involving a total of 10,301 patients. They concluded that elevated plasma TMAO levels increased the risk of major adverse cardiovascular events among patients with heart disease by 58%.

Another meta-analysis reveals a significant association between high levels of circulating TMAO and an increased risk of stroke.The study discusses potential mechanisms through which TMAO might increase the risk of stroke, including promotion of vascular plaque formation, endothelial dysfunction, prothrombotic changes, abnormal lipid metabolism, and increased inflammatory responses.

Plant-Based Diets

Transitioning to plant-based diets has been proposed as a strategy to mitigate the health risks associated with high TMAO levels. Plant-based diets are naturally low in the precursors of TMAO, offering a nutritional profile that supports cardiovascular health and reduces the risk of chronic diseases. A study in the Journal of Nutrition explored the effects of a plant-based diet on 23 meat-eating individuals with obesity or dysglycemia. Results indicated significant reductions in plasma TMAO and postprandial glucose levels after the plant-based diet, but TMAO levels increased after returning to the unrestricted diet. Improvements in TMAO levels were noted independently of weight loss, along with better lipid profiles and renal function. These findings suggest that a plant-based diet is an effective strategy for improving glucose tolerance and reducing plasma TMAO in individuals with dysglycemia or obesity.

A one-week lifestyle immersion program focusing on plant-based nutrition, stress management, and exercise was observed to significantly improve cardiovascular health markers in individuals at moderate to high risk for atherosclerotic cardiovascular disease (ASCVD). The study involved 73 participants and noted improvements in blood pressure, cholesterol, and triglycerides, without significant weight loss. Additionally, the program positively altered the intestinal microbiome, notably increasing beneficial butyrate-producing bacteria. These microbiota changes correlated with improvements in health markers such as BMI, blood pressure, cholesterol, and TMAO levels.

Conclusion

The evidence surrounding TMAO highlights its significant role in cardiovascular health, pointing to the metabolite as a pivotal factor in the development of cardiovascular diseases. Foods rich in choline and carnitine, predominantly found in animal products, have been implicated in the production of TMAO, thus linking diet directly with cardiovascular risk. On the flip side, studies illuminate the promising potential of plant-based diets and lifestyle interventions in mitigating these risks. Not only do plant-based diets inherently reduce TMAO levels, but lifestyle programs emphasizing plant-based nutrition, along with stress management and exercise, have shown remarkable benefits in improving cardiovascular markers and altering gut microbiota in favor of heart health. The collective findings from these studies underscore the profound impact of dietary and lifestyle choices on cardiovascular health, offering a beacon of hope for those at risk and underscoring the power of preventive, non-pharmacological approaches in combating cardiovascular disease.

References

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Li XS, Obeid S, Klingenberg R, et al.. Gut microbiota-dependent trimethylamine N-oxide in acute coronary syndromes: a prognostic marker for incident cardiovascular events beyond traditional risk factors. Eur Heart J. 2017;38:814–24.

Canyelles M, Borràs C, Rotllan N, Tondo M, Escolà-Gil JC, Blanco-Vaca F. Gut Microbiota-Derived TMAO: A Causal Factor Promoting Atherosclerotic Cardiovascular Disease? Int J Mol Sci. 2023 Jan 18;24(3):1940.

Tang WH, Wang Z, Levison BS, Koeth RA, Britt EB, Fu X, Wu Y, Hazen SL. Intestinal microbial metabolism of phosphatidylcholine and cardiovascular risk. N Engl J Med. 2013 Apr 25;368(17):1575-84.

Yao ME, Liao PD, Zhao XJ, et al. Trimethylamine-N-oxide has prognostic value in coronary heart disease: a meta-analysis and dose-response analysis. BMC Cardiovasc Disord. 2020;20(1):7.

Lombardo M, Aulisa G, Marcon D, Rizzo G. The Influence of Animal- or Plant-Based Diets on Blood and Urine Trimethylamine-N-Oxide (TMAO) Levels in Humans. Curr Nutr Rep. 2022;11(1):56-68. doi:10.1007/s13668-021-00387-9.

Ahrens AP, Culpepper T, Saldivar B, et al. A Six-Day, Lifestyle-Based Immersion Program Mitigates Cardiovascular Risk Factors and Induces Shifts in Gut Microbiota, Specifically Lachnospiraceae, Ruminococcaceae, Faecalibacterium prausnitzii: A Pilot Study. Nutrients. 2021;13(10):3459.