Heart disease is the number one cause of death worldwide, surpassing cancer, according to the World Health Organization. This year alone, nearly 700,00 deaths in America will be directly attributed to heart disease. For decades, diet and exercise have been known to affect your personal risk of getting heart disease, and red meat and saturated fat in dairy have both been ruled culprits in raising your risk, but the exact mechanism at work in the body has been hard to pin down. Until now.

A new study finally takes the guesswork out of exactly what happens in the body when you eat red meat, and why this mechanism in your gut raises your risk for blood vessel blockages, hardening of the arteries, and ultimately your risk for cardiovascular disease and potentially deadly events such as heart disease and stroke.

Compound Produced When You Eat Red Meat, Linked to Heart Disease

The new research shows that an organic compound produced in the digestive tract after eating red meat lead directly to a higher risk of developing cardiovascular disease.

Cardiovascular disease, a broader term for heart disease (since it encompasses circulatory problems that can lead to stroke) can take decades to show up in the body and is tied to several major risk factors including exercise habits, diet, smoking, and genetics. The symptoms can range from high blood pressure, high cholesterol, hardening of the arteries, high blood lipids, and plaque or calcium deposits which cause blockages in important arteries all of which are predictors of heart attack, heart failure and stroke.

Now, researchers from the American Heart Association have published a paper in the journal Arteriosclerosis, Thrombosis, and Vascular Biology (ATVB) that demonstrates that certain metabolites – substances released during the metabolism process of breaking down the food you eat – can directly drive up your risk of cardiovascular disease. That compound is called TMA or TMAO, when it combines with oxygen and high levels of it can be a risk factor.

Pay Attention to TMAO, New Research Finds

The researchers narrowed their study to focus on a metabolite produced by gut bacteria during red meat digestion, TMA, which when mixed with oxygen in the liver as it enters the bloodstream becomes TMAO, or trimethylamine N-oxide.

TMAO has already been associated with a higher risk of heart disease as well as the risk of diabetes and chronic kidney disease. The more TMAO in the body, the more likely a person will have plaque deposits that block circulation in the bloodstream and the so-called hardening of the arteries or atherosclerosis. Earlier studies have found a link between high levels of TMAO and a greater risk of cardiovascular disease, but to what extent was unclear.

TMAO levels, if elevated over time, are associated with poor circulation due to plaque deposits and atherosclerosis, which puts more strain on the heart to pump blood through the arteries, raising blood pressure and leading to cardiovascular disease.

High levels of TMAO have been linked to progressive cardiovascular disease and past studies have linked eating red meat to higher levels of TMAO. Meanwhile, eating plant-based (and avoiding red meat) appears to lower TMAO. To test this theory out, Stanford University researchers at the Quantitative Sciences Unit asked 36 participants to swap out red meat for plant-based alternatives for 8 weeks, and then switch back. Each time, the participants on the plant-based diet had lower TMAO at the end of the study.

Read More: Study: Eating 2 Plant-Based Burgers a Day Is Healthier for Heart

TMAO Leads to blockages, and eventually heart disease.

In an exclusive interview with The Beet, Dr. John Cooke, who is Chairman of the Department of Cardiovascular Sciences at Houston Methodist Research Institute, part of the Texas Medical Center, as well as Professor of Cardiovascular Sciences, and Member of the Academic Institute Director of the Center for Cardiovascular Regeneration, explains that you want the lining of the blood vessels to be smooth like Teflon, and not rough like velcro, and TMAO increases the stickiness of these epithelial cells that line your arteries, making it more likely you will develop plaque and blockages that can restrict blood flow.

The renewed focus on TMAO as the culprit in heart disease is a shift away from focusing attention on cholesterol levels as the main problem, according to the authors of the latest research. "Most of the focus on red meat intake and health has been around dietary saturated fat and blood cholesterol levels," author of the study Meng Wang, Ph.D., a postdoctoral fellow at the Friedman School of Nutrition Science and Policy at Tufts University in Boston, said. "Based on our findings, novel interventions may be helpful to target the interactions between red meat and the gut microbiome to help us find ways to reduce cardiovascular risk.”

Why is Red Meat Bad for Your Heart?

The new study found that eating more meat – especially red and processed meat – attributed to a 22 percent higher risk (per 1.1 serving per day) of cardiovascular disease. The researchers determined that an increase in TMAO and related metabolites found in blood samples explained some of the risks, while elevated blood sugar and general inflammation were other contributing risk factors.

The researchers examined the data of 4,000 participants from the Cardiovascular Health Study between 1989 and 1990. The study tracked dietary habits correlated to heart and cardiovascular disease risk and the researchers compared red meat consumption to incidents of cardiovascular disease over three decades. All participants were free of cardiovascular disease at the start of the study

"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," Wang said.

Eating Plant-Based Helps Avoid Heart Disease

Eating red meat presents severe risks for heart disease as you grow older. A review of 1.4 million meat-eaters from last July found that red meat consumption increases your risk for heart disease by 18 percent. The study noted that three mechanisms occur when you eat meat: saturated fat, TMAO, and high sodium. These three factors lead to a higher risk of stroke, heart attack, and heart failure.

Following a plant-based or plant-centered diet can help reduce the risk of heart disease 30 years later. In a previous review study, researchers found that eating more plant-based younger in life – starting at the early ages of 18 to 30 – helps lower the risk of heart disease decades later.

This March, yet another study found that the plant-based equivalent to conventional omega-3 fatty acids can significantly benefit heart health. Alpha-linolenic acid (ALA) can be found in several plant-based foods including chia seeds, walnuts, Brussels sprouts, and more.

Looking to incorporate heart-healthy meals into your diet? Check out The Beet's heart-healthy recipes! 

How to Get Enough Iron When You’re Following a Plant-Based Diet

You may think iron is synonymous with meat, and while animal protein certainly has it, that doesn’t mean you can’t get enough iron if you eat a mainly plant-based diet. In fact, you can, if you know the right foods to choose and how to pair them. The daily recommendation from the National Institutes of Health (NIH) for iron intake is 18 milligrams (mg), but not all iron sources are created equal. Here’s what plant-based eaters need to know about iron and which iron-rich foods are best to help reap the benefits.