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NMU – 213 High-Fat Diets Also Increase Heart Attack and Stroke Risk by Raising TMAO Blood Levels – A new risk factor of importance

Nutrition/Natural Medicine Update No 213 (September 9, 2021)

with Dr. James Meschino


Topic: High-Fat Diets Also Increase Heart Attack and Stroke Risk by Raising TMAO Blood Levels
– A new risk factor of importance

Source: journal Science (August 2021)


A new risk factor for heart disease and stroke has emerged in recent years, which is known as TMAO (Trimethylamine-N-oxide). High blood or urine levels of TMAO are shown to become elevated with high-fat diets and are strongly associated with major adverse cardiovascular events (MACE), such as heart attack or stroke. So, how does a high-fat diet increase TMAO blood and urine levels? Well, a study published in the journal Science in August 2021 showed that a high-fat diet disrupts the functioning of the intestinal lining (impairing mitochondrial function of intestinal epithelial cells that line the gut, causing intestinal cells to produce more oxygen and nitrate), and the gut microflora (the bacteria that normally live in the large intestine). In turn, this promotes the growth of more unfriendly gut bacteria, such as E. Coli (and other Enterobacteriaceae microbes). The unfriendly gut bacteria metabolize normal and healthy constituents (carnitine, choline, betaine) of certain foods we eat into TMA (Trimethylamine). The TMA then gets absorbed into the bloodstream and travels to the liver, where it is metabolized into TMAO and released into the circulation.

How does TMAO increase the risk of cardiovascular events? Experimental studies show that high levels of TMAO in the bloodstream accelerate the narrowing of the arteries (atherosclerosis), increase the risk of thrombosis or abnormal clots, and produce blood vessel inflammation – these are all important mechanisms that contribute to having a heart attack or stroke. So, to summarize, eating a high-fat diet damages the cells that line the intestinal tract and promotes the proliferation of unfriendly gut bacteria that convert certain desirable food constituents into trimethylamine (TMA). The TMA gets absorbed, travels to the liver, where it is converted into TMAO, which is then released into the circulation, where it increases the risk of heart attack and stroke.


It’s noteworthy that many of the same high-fat foods that raise blood cholesterol levels also elevate TMAO blood levels, producing a double-whammy effect on the risk of heart attack and stroke. Having a blood level of TMAO lower than 3.9 umol/L is considered safe, whereas a blood level above 5.1 umol/L is now considered to be a significant risk factor for having a major adverse cardiovascular event, such as a heart attack or stroke. The problem is that most doctors don’t order the TMAO blood test. You have to request it. So, this is another reason to avoid a diet containing unhealthy fats (especially beef, pork, high-fat dairy products, coconut oil, deep-fried foods, battered foods, pastries, etc.) and to also consider taking a probiotic supplement each day that contains a variety of gut-friendly bacteria, which help crowd out the unfriendly gut bacteria responsible for TMA synthesis. These two strategies (a healthy lower-fat diet and probiotic supplementation, and also consuming fermented foods that contain probiotics) can help you keep your TMAO blood level in the desirable range –  another important wellness strategy that can reduce your risk of having a heart attack or stroke.

I have included the references for this information in the text below.



1. Primary Reference: Woongjae Yoo, Jacob K. Zieba, Nora J. Foegeding, Teresa P. Torres, Catherine D. Shelton, Nicolas G. Shealy, Austin J. Byndloss, Stephanie A. Cevallos, Erik Gertz, Connor R. Tiffany, Julia D. Thomas, Yael Litvak, Henry Nguyen, Erin E. Olsan, Brian J. Bennett, Jeffrey C. Rathmell, Amy S. Major, Andreas J. Bäumler, Mariana X. Byndloss. High-fat diet–induced colonocyte dysfunction escalates microbiota-derived trimethylamine N-oxide. Science, 2021.

2. Journal American College Cardiology: 2020

3. BMC Cardiology: 2020

4. Journal American Heart Association: 2019

5. Uremic Toxicology: 2016


Eat Smart, Live Well, Look Great,


Dr. Meschino

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