When choline and carnitine are metabolized by the intestinal bacteria, a metabolite called trimethylamine-N-oxide (TMAO) can be formed.  TMAO triggers inflammation (Seldin MM, et.al., 2016).

Other researchers has also showed that TMAO induces inflammation and endothelial dysfunction (Sun X, et.al., 2016). The endothelium is the inner lining of the blood vessels, and endothelial dysfunction creates cardiovascular disease.

An elevated TMAO level predicted an increased risk of major adverse cardiovascular events after adjustment for traditional risk factors (Tang WH, et.al., 2013).

The researchers based their conclusion on data collected during 3 years of follow-up in 4007 patients undergoing elective coronary angiography.

They also had healthy people ingesting two hard-boiled eggs before and after the suppression of the intestinal microbiota with oral broad-spectrum antibiotics to see if the bacterial flora made a difference in the detected TMAO level.

The researchers found that levels of TMAO were markedly suppressed after the administration of antibiotics and then reappeared after withdrawal of the antibiotics.

This means that the bacterial flora has a lot to do with how much TMAO we are going to produce.


In humans, dietary l-carnitine is converted into the atherosclerosis- and thrombosis-promoting metabolite TMAO by gut bacteria (Koeth RA, et.al., 2019).

The researchers discovered that TMAO is induced by omnivorous dietary patterns and chronic l-carnitine exposure, because the TMAO was markedly lower in vegans and vegetarians.

If you eat a plant based diet and avoid animal based protein like dairy, eggs and red meat your gut bacterial flora will be different, and you will not produce TMAO.


Koeth RA, Lam-Galvez BR, Kirsop J, Wang Z, Levison BS, Gu X, Copeland MF, Bartlett D, Cody DB, Dai HJ, Culley MK, Li XS, Fu X, Wu Y, Li L, DiDonato JA, Tang WHW, Garcia-Garcia JC, Hazen SL. l-Carnitine in omnivorous diets induces an atherogenic gut microbial pathway in humans. J Clin Invest. 2019 Jan 2;129(1):373-387.

Seldin MM, Meng Y, Qi H, Zhu W, Wang Z, Hazen SL, Lusis AJ, Shih DM.Trimethylamine N-Oxide Promotes Vascular Inflammation Through Signaling of Mitogen-Activated Protein Kinase and Nuclear Factor-κB.J Am Heart Assoc. 2016 Feb 22;5(2). pii: e002767.

Sun X, Jiao X, Ma Y, Liu Y, Zhang L, He Y, Chen Y.Trimethylamine N-oxide induces inflammation and endothelial dysfunction in human umbilical vein endothelial cells via activating ROS-TXNIP-NLRP3 inflammasome. Biochem Biophys Res Commun. 2016 Dec 2;481(1-2):63-70.

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.


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  • Category: General Health
  • Author: Didrik Sopler
  • Published: 2020-03-30
  • Comments: 0
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