When I was a young post-graduate fellow, I had a patient with an “irritable heart” that tended to skip every third or fourth beat. Whenever he ate certain foods such as cabbage, bacon, or pork chops, he experienced bowel discomfort and palpitations.
I hadn’t learned anything in medical school about how heart disease affects the digestive system and vice versa, so with little else to fall back on, I gave the patient a common-sense recommendation: Stay away from fatty foods and cabbage. He did and his symptoms improved enormously.
This Alerted Me to the Gut-Heart Connection
I was fortunate to have had this experience early in my career as a cardiologist because it made me aware of the relationship between the heart and the gut. It’s not that heart problems cause digestive problems per se, or that digestive problems cause heart disease. Rather, the two systems are part of the whole, and what affects one can affect the other.
I began routinely prescribing extra fiber for my patients, and both their constipation and their symptoms of heart disease significantly improved. As they adopted a heart-healthy diet and exercise program, they had fewer digestive complaints as well as better heart function.
As more recent research on the far-reaching effects of the gut microbiota increased our understanding of the heart-gut connection, I made probiotics and other ways of nurturing gut health part of my program for improving cardiovascular outcomes.
You are no doubt aware that the gut microbiota—the trillions of bacteria and other microorganisms that reside in your intestinal tract—supports digestive health. These microbes break down fiber, provide fuel for the cells lining the colon, produce antimicrobial compounds that protect against pathogens, and fortify the intestinal walls, thus preventing leaky gut.
You may also know your gut plays a central role in immune function. About 70% of your immune system is housed in the intestinal lining, which is in direct contact with gut microbes—and there’s extensive crosstalk between the two. For instance, the gut microbiota helps “train” the immune system, thereby reducing allergies and autoimmune diseases.
But what you may not realize is the gut microbiota also generates a number of important substances that are utilized throughout your body. Some gut bacteria synthesize vitamin K and B vitamins. Others produce enzymes, inflammatory cytokines, and short-chain fatty acids such as butyrate that communicate and interact with the nervous, vascular, and endocrine systems—directly affecting your heart health.
Gut Microbiota & Cardiovascular Disease
Let’s look at a few of the most significant risk factors for cardiovascular disease and how they are influenced by the gut microbiome—for better or for worse:
- Cholesterol: Certain gut bacteria can actually transform cholesterol into another substance called coprostanol, resulting in lower blood cholesterol levels. Better yet, strains of Lactobacillus plantarum that are included in some probiotic supplements have been demonstrated to reduce total cholesterol by 33%. These probiotics also lowered triglycerides and oxidized LDL and increased protective HDL cholesterol.
- Hypertension: Researchers have found distinct alterations in the microbiota of individuals with hypertension. A reduction in butyrate-producing bacteria, for example, has been linked with elevated blood pressure. Other research suggests that a high sodium intake raises blood pressure in part by its adverse effects on the gut microbiota.
- Inflammation: A major risk factor for many chronic diseases, inflammation can be triggered by imbalances that enable pro-inflammatory microbes to gain the upper hand. Conversely, studies have shown that some bacteria, including those that produce short chain fatty acids, have anti-inflammatory properties.
- Obesity: Because your gut microbiota influences your metabolism, energy expenditure, and even your appetite and food cravings, it helps determine if you are overweight. Obese individuals tend to have less microbial diversity and greater concentrations of certain bacterial species, compared to lean people. Plus, a number of studies have linked obesity with the use of antibiotics, which significantly alter the microbiota.
- Diabetes: The gut microbiota also plays a role in insulin signaling and blood sugar control. A recent review study in an online Lancet journal identified bacterial species from the genus Bifidobacterium that appear to be protective against type 2 diabetes—and other types that are more abundant in individuals with diabetes. This, along with its effects on weight and inflammation, underscores the association between the gut microbiota, diabetes, and its complications, which include heart disease.
Gut Microbes Under Fire
Ideally your gut is host to a wide diversity and balance of bacteria. Unfortunately, this delicate ecosystem is easily damaged, resulting in die-off of beneficial bacteria and overpopulation of undesirable strains. These imbalances, called dysbiosis, set the stage for a host of health challenges.
Among the most significant threats are antibiotics, which indiscriminately mow down all bacteria, both good and bad, and seriously alter the gut microbiota. According to the CDC, pharmacies dispense more than 270 million antibiotic courses every year! To add insult to injury, at least 30% of them are completely unnecessary, and another 20% are used inappropriately.
Additional threats include antibiotic residues in meat and other foods, chlorine in tap water, sugars, food additives, and stomach acid-reducing proton pump inhibitors. All of these significantly disrupt the balance and diversity of your gut bacteria.
Nurture Your Gut, Support Your Heart
So, what can you do to support your gut microbiome—and, incidentally, improve your cardiovascular function and overall health? Here is the program I recommend:
- Take probiotics. The benefits of these supplements, which contain billions of beneficial bacteria, for numerous conditions are supported by a growing body of research. Look for a product from a reliable manufacturer that contains a minimum of 12 billion CFUs of various strains of Lactobacillus, Bifidobacteria, and other supportive species.
- Eat more fiber. Fiber of all kinds is great, and I heartily recommend eating lots of fiber-rich plant foods. But make sure you include prebiotics, a specific type of fiber that encourages the growth of beneficial gut bacteria. Prebiotic fibers are broken down by gut microbes in a fermentation process that results in the production of short chain fatty acids, vitamins, and other important substances. Aim for at least 25–30 g of fiber a day—and don’t forget to include onions, garlic, oat, barley, flaxseed, and other sources of prebiotics.
- Cut out sugars and food additives. Sugars and refined carbohydrates contribute to the overgrowth of less desirable microbes and imbalances in the gut microbiota. Artificial sweeteners and other food additives such as emulsifiers, which are used in many processed foods to improve texture and extend shelf life, also adversely affect beneficial bacteria.
- Clean up your diet. Try to eat antibiotic-free meat, poultry, and eggs. Avoid GMOs, as they may contain traces of glyphosate, an herbicide that disrupts the gut microbiota.
- Include fermented foods. Yogurt, miso, and unpasteurized sauerkraut, kimchi, and other fermented foods that contain live and active cultures help repopulate your gut with health-enhancing bacteria.
- Drink filtered water. Chlorine is added to municipal water supplies to kill infectious organisms, but it can also take a toll on your gut microbes. A home water filtration system is, over time, the most economical way to go.
- Be aware of drug effects. Never take an antibiotic unless it is absolutely essential, and look for safer alternatives to Prilosec, Prevacid, and other proton pump inhibitors. Recent research suggests that metformin, SSRI antidepressants, and laxatives also change gut microbial composition and function.