How meat, gut bugs, and heart disease are connected
Intestinal microbiota metabolism of L-carnitine, a nutrient in red meat, promotes atherosclerosis
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
When people eat red meat, a substance called L-carnitine gets broken down by certain gut bacteria into a chemical called TMAO, which can cause heart disease. People who eat meat regularly have more of these bacteria and make more TMAO. Vegans and vegetarians don’t make much TMAO from L-carnitine.
No biological mechanisms were identified in this study. This may be an epidemiological, observational, or survey-based study that reports associations rather than proposing causal biological pathways.
Systematic Reviews & Meta-Analyses
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Evidence Score
Groups of people are followed over time to see who develops an outcome. Strong for identifying risk factors and associations, but cannot prove causation as firmly as RCTs.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
When people eat red meat, a substance called L-carnitine gets broken down by certain gut bacteria into a chemical called TMAO, which can cause heart disease. People who eat meat regularly have more of these bacteria and make more TMAO. Vegans and vegetarians don’t make much TMAO from L-carnitine.
No biological mechanisms were identified in this study. This may be an epidemiological, observational, or survey-based study that reports associations rather than proposing causal biological pathways.
Systematic Reviews & Meta-Analyses
Max 100Randomized Controlled Trials
Max 90Cohort Studies
Max 72Case-Control Studies
Max 58Cross-Sectional Studies
Max 44Case Reports & Case Series
Max 30Expert Opinion & Narrative Reviews
Max 561 / 72
Evidence Score
Groups of people are followed over time to see who develops an outcome. Strong for identifying risk factors and associations, but cannot prove causation as firmly as RCTs.
Publication
Authors
Koeth RA, Wang Z, Levison BS, Buffa JA, Org E, Sheehy BT, Britt EB, Fu X, Wu Y, Li L, Smith JD, DiDonato JA, Chen J, Li H, Wu GD, Lewis JD, Warrier M, Brown JM, Krauss RM, Tang WH, Bushman FD, Lusis AJ, Hazen SL
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Claims (5)
If you eat meat and take L-carnitine, your gut bacteria might turn it into a substance that could clog your arteries. But if you're vegan or vegetarian, your gut bugs don’t do this much, so you’re less likely to make that substance.
If someone has high levels of L-carnitine in their blood, they might be more likely to have heart problems — but only if they also have high levels of another substance called TMAO.
Giving mice a supplement called L-carnitine every day makes artery disease about twice as bad, but if you wipe out their gut bacteria with antibiotics, that effect goes away — meaning the gut bugs are behind the harm.
In mice, certain nutrients and a gut chemical they produce can slow down the body's ability to remove cholesterol — but only if the gut bacteria are active.
The kinds of gut bacteria you have, especially if you eat a lot of meat, might be linked to higher levels of a substance in your blood called TMAO, which could mean your diet over time helps shape which bacteria stick around.