Researchers in the Cleveland Clinic in Ohio have discovered a surprising new connection between red meat and heart risk that involves bacteria living in the gut. Gut bacteria digest L-carnitine, a compound abundant in red meat and added to popular energy drinks, to produce trimethylamine-N-oxide (TMAO), a metabolite already suspected of helping to clog up arteries.
Previous studies that have tied red meat consumption to increased cardiovascular risk have shown while some of the raised risk is due to the fat
and cholesterol in red meat, these culprits aren’t enough to explain all of it.
Researchers have pointed to other factors, such as genetic differences, a diet high in salt, which is often linked to red meat consumption, and even
the way the meat is cooked.
But this latest study, led by Stanley Hazen of the Cleveland Clinic in Ohio, and published online in Nature Medicine this week, offers a new
link between red meat and heart risk.
Hazen is section head of Preventive Cardiology Rehabilitation in the Miller Family Heart and Vascular Institute at the Cleveland Clinic.
In 2011, the researchers reported a study where they linked TMAO to the promotion of atherosclerosis (where arteries get clogged up by
cholesterol and other fatty compounds) in humans.
In this latest study, Hazen and colleagues discovered human gut bacteria turn L-carnitine into TMAO.
They also found that a diet high in L-carnitine encourages the growth of the bacteria that metabolize it, thereby boosting the production of even more artery-clogging TMAO.
Hazen, who is also Vice Chair of Translational Research for the Lerner Research Institute at the Cleveland Clinic, says in a statement:
“The bacteria living in our digestive tracts are dictated by our long-term dietary patterns.”
“A diet high in carnitine actually shifts our gut microbe composition to those that like carnitine, making meat eaters even more susceptible to
forming TMAO and its artery-clogging effects,” he adds.
The researchers also found that the gut of vegans and vegetarians is significantly less able to make TMAO from carnitine, which may explain the
cardiovascular health benefits of their diets.
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