Why Red Meat Really Increases Heart Disease Risk, Study Reveals

In "Annie Hall" (1977), one of the main characters laments, "Everything our parents said was good is bad. Sun, milk, red meat, college." While the jury might still be out on the other three (depending on who you ask), a new study reveals that red meat is, in fact, linked to heart disease, and it's a major problem around the world.

According to the World Health Organization, cardiovascular disease (CVD) is the number one cause of death in the world. In fact, it says, CVD is responsible for 17.9 million global deaths every year, with 655,000 deaths in the U.S. alone, per the Cleveland Clinic. Diabetes, tobacco use, obesity, inactivity, excessive alcohol consumption, and a diet high in sugars, salts, and fats all increase a person's risk of developing CVD. The way it works, explains the American Heart Association, is plaque builds up in the arteries, causing them to narrow and subsequently restrict blood flow to the heart. Nearly 50% of all U.S. adults are living with at least one type of heart disease, which can include arrhythmia, coronary artery disease, and congenital heart disease, among others (via the Cleveland Clinic).

Now, experts are turning their attention toward red meat. According to WebMD, red meat has one of the highest saturated fat contents of any food, but it isn't even the saturated fat content that researchers are concerned about this time. Another chemical might be to blame for heart disease — and your body produces it naturally.

The study was published earlier this month in the American Heart Association's peer-reviewed journal "Arteriosclerosis, Thrombosis, and Vascular Biology" (ATVB), via ScienceDaily. After studying nearly 4,000 test subjects, researchers concluded that eating 1.1 servings of red meat per day was linked to a 22% higher risk of developing CVD compared to participants who followed plant-based diets or ate other animal proteins. Fish, poultry, and eggs did not increase test subjects' risk for developing cardiovascular disease.

The culprit is a digestive enzyme. When a person eats red meat, it stimulates microbes in the stomach to produce a chemical called L-carnitine, which in turn produces trimethylamine N-oxide (TMAO). High levels of TMAO in the blood are directly linked to a higher risk of heart disease, and it's produced when the body tries to digest red meat. Other contributing factors to heart disease (like inflammation, high blood pressure, and cholesterol) were not associated with TMAO production, the study found,

Another 2013 study led by Dr. Stanley L. Hazen and Robert A. Koeth of the Cleveland Clinic similarly determined that there might be a link between carnitine and heart disease. "The composition of bacteria living in our digestive tracts is dictated by our long-term dietary patterns," Hazen explained via the National Institutes of Health. "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, which helps promote atherosclerosis."

It's no secret that following a heart-healthy diet can stave off the risk of cardiovascular disease. According to Healthline, leafy greens like spinach and kale, whole grains like oats and brown rice, berries, avocados, salmon, walnuts, almonds, tomatoes, and beans are among the most heart-healthy foods a person can add to their regular diet. These small changes can make a big difference. A meta-analysis of eight different studies synchronized by Richard Lee Pollock of Lamar State College Port Arthur concluded that incorporating more leafy green vegetables into a person's diet decreases the risk of cardiovascular disease by 16%, via the National Library of Medicine.

Wang, the recent American Heart Association study's co-lead author, calls for other researchers to conduct similar studies to broaden our understanding of how red meat can affect the body. "Research efforts are needed to better understand the potential health effects of L-carnitine and other substances in red meat such as heme iron, which has been associated with Type 2 diabetes, rather than just focusing on saturated fat," says Wang, via ScienceDaily.