There's a revolution going on in our understanding of the cause of heart disease. And that revolution is a new connection between bacteria in our GI tract and the risk of developing clogged arteries.
We've known for years that not all cases of heart disease, the #1 killer in the Western world, are explained by the traditional risk factors such as smoking, elevated blood pressure, diabetes mellitus, high cholesterol, and a family history of premature heart disease. And so a few years ago researchers at the Cleveland Clinic began searching for new causes of heart disease.
The researchers focused on a compound called TMAO or tri-methyl amine oxide. This molecule, new on the scene, is produced by intestinal bacteria as a result of our dietary choices, particularly foods rich in choline and l-carnitine, like eggs and red meat. For example, subsequent research has shown that feeding l-carnitine to subjects, in the form of a steak, produced major rises in TMAO. And other studies have shown that when volunteers ate eggs — choline is concentrated in egg yolks — their blood level of TMAO rose quickly.
In the Cleveland Clinic study, the researchers showed that TMAO increased the accumulation of cholesterol in the wall of arteries to begin plaque buildup. Further work has also shown that TMAO prevents cleaning up of cholesterol-diseased arteries, so it's a double whammy. In the studies at the Cleveland Clinic in more than 4,000 patients, the higher the blood level of TMAO, the more advanced and severe was the heart disease.
The researchers proved it was the bacteria in the GI tract that was producing TMAO because a short course of antibiotics that wiped out GI bacteria also temporarily wiped out TMAO production.
Next, to determine if omnivores are predisposed to heart disease due to their dietary choices, the team recruited vegans and paid them to eat eggs or steak and measured TMAO blood levels. What happened? Nothing. Vegans have different bacteria in their GI tract. It appears that due to long-term dietary choices, the enzyme that converts these food sources to TMAO is absent, or nearly so, in vegans.
So what's brand-new in TMAO research? It's now known that TMAO causes scar tissue in kidneys and is both a marker of kidney damage and directly injures kidneys. Furthermore, elevated TMAO levels in congestive heart failure are now established and TMAO may scar the heart, too.
In terms of a remedy, so far one study of a potent probiotic failed to halt TMAO production. And while an inhibitor of TMAO production, DMB, has been described in animal studies, the safety in humans will need further study.
For now, avoiding or limiting dairy, eggs, and meat is a wise path to improve your health and help prevent numerous chronic diseases including heart disease, cancer, adult diabetes, and obesity. You can also consider having your blood tested for TMAO levels to help predict your cardiovascular risk. My heart prevention clinic is one of the first to offer the new lab test, and as some of my patients are showing very high levels, I've been advising them of dietary changes. So when people ask where you get your protein, a new response is “Where do you get your TMAO?"