The Gut-Heart Connection: How the Microbiome Influences Heart Health

Heart disease is the leading cause of death in the Western world, and a growing body of research has encouraged scientists to examine the role of the gut in its development. Dubbed the gut-heart connection, this relationship explains how the gut microbiome can influence cardiovascular health. 

Stemming from a wealth of research, we’ve learned that supporting a healthy gut may help maintain a healthy heart. Future approaches to the prevention and treatment of heart disease may involve microbiome testing and the use of probiotics.

Heart disease in the United States 

According to the CDC, heart disease is the most common cause of death for both men and women in the United States, accounting for one in every four fatalities. 

The resulting burdens placed on society, healthcare systems, and the economy have prompted a great deal of research, education, and innovation to prevent and treat the disease.

Despite the sizeable efforts that have gone into healthy eating guidelines and medical advances, cardiovascular disease rates remain strikingly high. 

Is there a missing link when it comes to heart health? 

The future of medicine may rely, in part, on understanding the connections between organs and systems that we have long treated as separate. When it comes to cardiovascular health, it turns out the gut may have a major role to play. 

Gut health and heart health are intertwined in a number of ways. For starters, the risk of developing heart disease is higher in those diagnosed with a gastrointestinal condition. Similarly, if you have previously been diagnosed with a cardiovascular condition, the chances are higher that you’ll develop a gastrointestinal problem in the future.

Research is now zeroing in on the role of the gut microbiome as a prominent factor in the development of heart disease. 

Cardiovascular risk factors and the gut 

According to the CDC, nearly half of Americans have at least one of the three primary risk factors for cardiovascular disease. These include high blood pressure, high cholesterol levels, and smoking. 

Other risk factors include family history, obesity, diabetes, age, lack of exercise, an unhealthy diet, inflammation, elevated TMAO levels, and hormonal imbalances, including leptin or insulin resistance. 

Although you can’t control all of these risk factors, you can modify some through healthy lifestyle habits. Looking into the modifiable risk factors for heart disease, we find that many relate to gut health. 

Gut dysbiosis and the heart 

An imbalance between healthy and pathogenic bacteria within the gut microbiome, referred to as dysbiosis, has been linked to heart disease and a number of its risk factors.

Research has revealed significant differences between the gut microbiomes of those with atherosclerosis and healthy individuals. Those with chronic heart failure also tend to have dysbiosis and insufficient bacterial diversity in the gut. 

One 2018 study in the European Heart Journal linked low gut diversity to increased arterial hardening in women. The researchers were also able to identify some of the specific bacterial species related to arterial hardening. Notably, in this study, gut bacteria were more likely to influence arterial stiffness than other well-known risk factors, including obesity and insulin resistance. 

The microbiome may also play a role in other risk factors for heart disease, such as obesity and high cholesterol levels. 

The connection between SIBO and heart disease

Coronary Artery Disease (CAD), a blockage or narrowing of the coronary arteries due to plaque buildup, is the most common heart disease and the leading cause of death in the United States. 

Inflammation is a driving factor in the development and progression of CAD. Imbalances within the gut microbiome are linked to inflammation within the coronary arteries. 

Researchers have now identified a relationship between CAD and Small Intestinal Bacterial Overgrowth (SIBO). 

SIBO is a condition in which excessive bacteria lives in the small intestine. Experts estimate that roughly 20% of Americans have SIBO, undiagnosed or not. Among the population with Irritable Bowel Syndrome (IBS), this number jumps to as high as 78%. 

A recent study involving almost 1,000 patients found that those who had SIBO, as diagnosed by a standard glucose breath test, had a significantly higher chance of developing CAD. Those with SIBO also had more coronary arteries affected than those who didn’t have SIBO. 

The future of SIBO and CAD treatment 

What does this mean for the treatment of both SIBO and CAD? For starters, we may begin to look at SIBO and other imbalances within the gut microbiome as a risk factor for heart disease. This risk should be monitored and addressed on the same scale as blood sugar levels or obesity.

Future research will examine whether treating SIBO, likely with antibiotics and probiotics, can also help prevent or treat heart disease. 

The bidirectional relationship between the gut and the heart 

At this stage, research has not made clear whether SIBO leads to CAD or vice versa. In fact, the answer might be both. Researchers have suggested that, as with the gut and the brain, the gut-heart connection may involve a bidirectional relationship.

For example, excess bacterial byproducts produced as a result of SIBO may lead to an increased risk of CAD. Meanwhile, inflammatory cytokines (proteins) released as a result of CAD may disrupt the balance of the gut microbiome. 

TMAO and the gut 

One of the most intriguing links between the gut and the heart involves Trimethylamine N-oxide (TMAO), a compound linked to artery-clogging plaque formation.  

Several studies have connected high levels of TMAO to a significantly increased risk of heart disease. In one large cohort study, researchers used TMAO levels alone to predict major cardiac events (such as heart attacks), independent of other risk factors. 

TMAO is produced within the body when certain microbes within the gut feed on choline. Because certain foods like eggs, poultry, and red meat contain high choline levels, experts have advised limited consumption of these foods for those at risk for heart disease.

Interestingly, emerging research is looking more closely at the types of bacteria that produce TMAO. They’re finding that high levels of TMAO may have more to do with an imbalance in the gut microbiome itself than with the consumption of choline-rich foods. 

These findings may mean that correcting gut dysbiosis can help keep TMAO levels in check, reducing the risk of plaque formation and heart disease. 

Leaky gut and the heart 

Research has shown that patients with chronic heart failure are more likely to have altered intestinal function, including increased intestinal permeability.

Intestinal permeability, often referred to as “leaky gut syndrome,” occurs when the intestinal lining becomes compromised, allowing food particles and bacteria to “leak” out into the bloodstream. 

As the body reacts to these foreign substances in the bloodstream, inflammation occurs. Eventually, this inflammation can become chronic and widespread, causing inflammatory diseases that affect different areas of the body. 

This may explain the connection between intestinal permeability and heart disease, as inflammation is connected to arterial plaque. 

An impaired gut lining can also cause molecules linked to CAD called lipopolysaccharides (LPS) to enter the bloodstream. 

Benefits of SCFAs for heart health 

Microbes within the gut produce short-chain fatty acids (SCFAs), which are involved in many physiological functions. Some SCFAs like butyrate help protect the heart by regulating blood pressure, improving insulin sensitivity, and increasing expression of the hormone leptin, which is related to appetite and body weight. 

Because gut microbes produce butyrate through the fermentation of dietary fiber, a high-fiber diet with prebiotics may be recommended for optimal heart health. 

What does the gut-heart connection mean for the treatment of heart disease? 

As researchers continue to uncover the connections between the gut and the heart, it may eventually become commonplace to target gut health to prevent or treat heart disease.

This may involve gut microbiome testing as a predictor of heart disease risk, increased collaboration between gastroenterologists and cardiologists, and gut-focused treatments like probiotics for cardiovascular disease.

Tips for optimal gut-heart health 

Many different factors can contribute to heart disease, and supporting a healthy gut may be one critical piece of the puzzle. 

What can you do to promote a healthy, diverse gut microbiome for reduced heart disease risk and improved overall well-being? Here are a few tips. 

Probiotics for gut and heart health 

Given the connection between the gut microbiome and heart health, probiotics may be a helpful first step in strengthening your gut-heart connection. 

More research is needed before doctors can recommend probiotics as a standard preventative measure or treatment for heart disease, but preliminary research has shown promise. The cost-effectiveness and general safety of probiotics also make them an attractive option for prevention.

Research has found that supplementing with probiotics can help reduce blood pressure, particularly among those with higher baseline blood pressure. 

Certain species of probiotics, including Lactobacillus reuteri and Bifidobacterium longum, have also been shown to reduce blood cholesterol levels in animals and humans. 

One study found that probiotic therapy reduced systemic inflammation and improved left ventricular ejection fraction, one marker of cardiac function.

The use of prebiotics (food for probiotics) may also help reduce risk factors for heart disease, including cholesterol and triglyceride levels. 

Make sure to choose a high-quality probiotic with high manufacturing standards and research-backed strains. 

Other tips 

• Pay attention to gastrointestinal symptoms. We know that gut distress can be a sign of distress elsewhere, including cardiovascular issues. Symptoms like gas, bloating, or constipation may be signs that something bigger is amiss and should be addressed by a physician.
• Cut back on sugar. What we eat affects the makeup of our gut microbiome. Sugar and refined carbohydrates negatively impact the gut microbiome and promote gastrointestinal inflammation, so avoid these when you can.
• Eat plenty of healthy fiber. Our friendly gut microbes rely on dietary fiber to make beneficial short-chain fatty acids. Studies have also found an association between fiber intake and reduced risk of cardiovascular disease. Healthy sources of fiber include fresh fruits and vegetables, barley, beans, and nuts.
• Limit your use of NSAIDs and antibiotics. Antibiotics and NSAIDs (including Advil and Aspirin) have been linked to imbalances within the gut microbiome. Try to use these medications sparingly, if possible.

In summary 

Cardiovascular disease is the leading cause of death in the United States. As rates continue to rise, researchers are beginning to look more closely at the role of a gut-heart connection. 

The relationship between the gut and the heart may be bidirectional, with gut health influencing cardiovascular health and vice versa. 

The gut microbiome has been linked with many modifiable risk factors for heart disease, including blood pressure, cholesterol, obesity, and inflammation. Imbalances within the gut microbiome have also been linked to an increased risk and prevalence of heart disease. 

Some of the links between gut and heart include an increased incidence and severity of Coronary Artery Disease (CAD) among those with Small Intestinal Bacterial Overgrowth (SIBO), the influence of gut microbes on the production of TMAO, and increased intestinal permeability among those with heart disease. 

Supporting a healthy gut may be an important component of maintaining heart health. As research continues to advance, gut microbiome testing and the use of probiotics and prebiotics may become more commonplace for the prevention and treatment of cardiovascular disease.  

Ellie Ellias - Contributing Writer, Physician’s Choice 

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