When most people think of their risk for having a heart attack or stroke, factors like cholesterol and blood pressure come to mind. But a new study by researchers at Cleveland Clinic shows that what’s in your gut can play a role as well.
The research, led by Stanley Hazen, MD, PhD, Section Head of Preventive Cardiology, shows that a compound that occurs in your gut after eating meat or high-fat dairy is a risk factor that can occur even if you have low cholesterol and a healthy blood pressure. The compound, called trimethylamine-N-oxide (TMAO) is formed when microbes in your gut digest foods such as red meat and egg yolks.
The new findings build on several clinical studies — many by Dr. Hazen’s research team — that link elevated blood levels of TMAO with heightened risk of heart and vascular diseases, including atherosclerosis, heart failure and chronic kidney disease. Several substances that are abundant in meat or dairy turn into TMAO after they come in contact with microbes in the gut.
How TMAO acts
Your digestive tract is full of bacteria. Some of them feed on choline and carnitine, which are nutrients in red meat, egg yolks and high-fat dairy products. As they feed, they give off a chemical called TMA (trimethylamine). Your liver turns TMA into TMAO.
TMAO in your blood affects the inner wall of your blood vessels, causing cholesterol buildup. TMAO also is dangerous because it heightens platelet activity, which can contribute to the formation of vessel-clogging blood clots.
Previous studies have shown that levels of TMAO in your blood can help predict your risk of heart disease. If you have chronically high TMAO, you have double the risk of heart attack, stroke and death.
The most recent study reviewed data from 4,000 patients and found that blood TMAO levels were a strong predictor of heart attack and stroke, independent of other risk factors.
“What we found is that TMAO identifies people at risk independent of their traditional risk factors, and in particular, it seems to help identify people at increased thrombotic event risk,” Dr. Hazen says.
Because TMAO is diet-induced, the study results open the door to new therapeutic targets and possible nutritional interventions as a way to prevent cardiac events, Dr. Hazen says.
Dr. Hazen also believes that this new information can give patients another way to manage their risk factors and improve their heart health.
Make changes for the better
One of the known ways to lower the production rate of TMAO involves following a diet that is focused on plants.
“A way of lowering your TMAO is to change your diet. It has been shown, and reported by others, that a Mediterranean diet, for example, will lower TMAO production overall,” Dr. Hazan says.
In addition to dietary changes, Dr. Hazen says people with a high TMAO should look at a number of ways to lower cardiovascular risk, including more aggressive monitoring of cholesterol levels and high blood pressure, and routine cardio exercise.
If you’re concerned about heart disease, here’s another reason to consider setting down your steak knife. A new study adds to a growing body of literature linking red meat consumption with increased heart disease risk.
Researchers have found that when we eat red meat, there is a set of reactions mediated by microbes in our gut. These gut microbe reactions are triggered by carnitine, a nutrient found in red meat. The study found that these reactions, which were previously unrecognized, contribute to the development of heart disease.
“This adds to the growing body of data reinforcing a connection between red meat, carnitine ingestion and heart disease development,” says Stanley Hazen, MD, PhD, Vice Chair of Translational Research for the Lerner Research Institute and Section Head of Preventive Cardiology & Rehabilitation. Dr. Hazen led the study.
How this research builds on past studies
A previous study linked carnitine to the development of narrowing or hardening of the arteries, also called atherosclerosis, but this latest research took it a step further. It uncovered more details about a chain of reactions generated when microbes in the gut digest the carnitine in red meat.
Dr. Hazen says the results help us better understand how eating red meat is related to heart disease. It also allows researchers to develop better tools to fight it.
“We are now a step closer to developing drugs or tools to retard or block the development of heart disease by this pathway,” he says.
Past findings related to red meat and heart disease risk include:
- Discovery of a biomarker that identifies risk of heart disease: trimethylamine-N-oxide (TMAO). There is a global hunt in progress using cardiovascular fingerprints — scientists call them biomarkers — to identify the risk of heart disease. The most common biomarker for heart disease is the blood test for cholesterol levels, but a more recent example is C reactive protein (CRP). In 2011, researchers discovered TMAO, which is made by microbes that live in your gut. Read the full story: Finding Heart Risk Through the Gut (Video).
Research in 2013 reports the discovery that carnitine, abundant in red meat and also added to popular energy drinks, is metabolized to TMAO, a compound linked to clogged arteries. Read the full story: Protect Your Heart: Limit Red Meat (Video).
Finding that choline, a nutrient contained in egg yolks and fatty meats, also produces the byproduct TMAO. Read the full story: Gut Bacteria Byproduct Predicts Heart Attack and Stroke (Video).
A study of middle-aged Seventh-day Adventists, a group with historically lower rates of cardiovascular disease than the general population, suggests that a more vegetarian dietary pattern may be associated with reduced mortality and increased longevity. Read the full story: Should I Cut Meat From My Diet?
Should you change your diet?
Deciding whether or not to eat red meat is a very personal choice, Dr. Hazen says.
“These studies do offer some powerful reasons to consider dropping or limiting red meat. It’s important to talk to your doctor. He or she can advise you based on your personal health history and individual heart disease risk.”