Why Your Microbiome Matters For Heart Health
Within the intricate folds of our large intestine lives upwards of 100 trillion bacteria, impacting our lives more than we know. Known as the gut microbiome, this collection of bacteria that resides in our intestinal tracts is, of course, vital to our digestive health, but more and more research is showing just how essential it is to our whole body—including the heart.
In a newer area of study known as the gut-heart axis, researchers are investigating how the bacteria and metabolites in our digestive tracts influence our cardiovascular system and how nourishing our gut microbiomes may also protect our hearts.
How Your Microbiome Impacts Your Heart
The microbiomes of people with cardiovascular conditions have been found to be different than healthy individuals, with alterations in gut bacteria species and metabolites. Imbalances in healthy versus unhealthy bacteria—a state known as gut dysbiosis—and reductions in beneficial compounds called short-chain fatty acids can play a role in the development of cardiovascular conditions.
Inflammation and Short-Chain Fatty Acids
Chronic inflammation is a known risk factor for heart conditions, and the balance of the gut microbiome can influence inflammatory responses in the body. Certain bacteria in the gut produce substances that can either promote or lower inflammation, affecting cardiovascular health.
A primary mechanism by which the microbiome affects inflammation is through the production of short-chain fatty acids (SCFAs)—butyrate, acetate, and propionate—which are created when dietary fiber is fermented in the gut. These compounds help to reduce inflammation, protect the intestinal lining, and keep the microbiome diverse by being a food source for healthy bacteria to thrive. A strong gut lining prevents intestinal permeability, which is involved with heart health because a so-called “leaky gut” leads to pro-inflammatory bacterial metabolites being able to circulate in the blood.
Research has shown that people with coronary heart conditions have lower amounts of gut bacteria that produce SCFAs—especially butyrate. This suggests that reduced amounts of SCFAs may have a detrimental effect on cardiovascular health.
TMAO
Trimethylamine N-oxide (TMAO) is a metabolite produced by some gut microbes. Certain bacteria can convert dietary compounds (typically those found in animal products) into a substance called trimethylamine (TMA), which is then metabolized into trimethylamine N-oxide (TMAO). Phyla of bacteria, such as Firmicutes, Proteobacteria, and Actinobacteria, are potential TMA producers, while Bacteroidetes appear unable to make TMA.
Elevated levels of TMAO have been associated with an increased risk of cardiovascular conditions, as it is believed to contribute to arterial stiffening and plaque development. However, the research on TMAO and heart health is not always conclusive and needs to be studied more to understand just how TMAO affects the cardiovascular system, especially since many foods that increase TMAO (like seafood, full-fat dairy, and eggs) are beneficial to health.
Immune System Health
As 70 to 80% of the body’s immune cells can be found in the gut, it has become increasingly apparent that the function of our microbiome plays a role in the function of our immune system, which, in turn, can influence cardiovascular health.
The heart and the immune system are constantly communicating through hormones and signaling molecules called cytokines. The microbiome is a part of this crosstalk because it’s involved in the adaptive immune system.
Adaptive immune cells called T and B cells are located in the gut-associated lymphoid tissue (GALT) of the intestinal walls. These cells act as microbial sensors by suppressing overreactions to harmless bacteria while recruiting other immune cells to the gut if a harmful microbe is present. B cells recognize foreign antigens and produce antibodies to target and eliminate that pathogen. The T cells are involved in cell-mediated immunity, which activates other immune cells like cytokines and phagocytes to kill pathogens.
The bacteria in our gut enhance the adaptive immune response by inducing T-cell differentiation. Naive T cells can modify themselves into several mature T cells, including natural killer cells and T helper cells, such as Th1, Th2, and regulatory T cells (T-regs). Recent research has found a unique population of T-regs with cardioprotective properties, and natural killer cells are vital for protecting against cardiac injury, fibrosis, and inflammation.
Cardiovascular Risk Factors
The gut microbiota also influences various risk factors for cardiovascular dysfunction, including blood pressure, blood sugar, and lipid and cholesterol levels. Gut dysbiosis has been linked to adverse changes in lipid profiles that contribute to cardiovascular risk, including higher LDL and lower HDL levels, as well as higher blood pressure.
This may be mediated by SCFA activity, as these microbe-produced fatty acids play a role in blood pressure regulation, blood sugar regulation, and lipid metabolism. SCFAs have been shown to lower cholesterol synthesis rates, leading to lower blood cholesterol levels.
Top Ways to Support Your Gut Microbiome
- Eat foods naturally containing probiotics, like fermented vegetables, sauerkraut, kimchi, yogurt and kefir.
- Consume foods high in prebiotics, which are fibrous compounds that healthy gut bacteria can feed on to stay alive in the gut. Prebiotic-rich foods include onions, garlic, apples, leeks and less-ripe bananas.
- Take a high-quality probiotic supplement that contains at least 1 billion CFU (colony-forming units) of healthy bacteria per capsule. Multi-strain probiotics are typically recommended for general gut health, while higher amounts of single-strain bacteria can target specific health concerns.
- Limit added sugar and refined carbohydrates, which do not contain the fiber your gut microbes need to survive. In addition, excess sugar intake negatively impacts your gut microbial ecosystem by decreasing bacterial diversity.
- Exercise. Regular physical activity has been shown to enhance the number of beneficial microbial species and enrich bacterial diversity.
Key Takeaways:
Our gut microbiomes do much more than aid digestion—they also play a vital role in protecting cardiovascular health. Many gut microbes or microbe-produced metabolites (like short-chain fatty acids and TMAO) influence heart health, for better or for worse. Some act on inflammatory pathways, while others alter cholesterol synthesis and immune cell signaling. There are many ways to improve the health of your gut microbiome, including eating a diet rich in prebiotics and probiotics, exercising regularly, and limiting your consumption of added sugar.
References:
Bui TVA, Hwangbo H, Lai Y, et al. The Gut-Heart Axis: Updated Review for The Roles of Microbiome in Cardiovascular Health. Korean Circ J. 2023;53(8):499-518. doi:10.4070/kcj.2023.0048
Canyelles M, Borràs C, Rotllan N, Tondo M, Escolà-Gil JC, Blanco-Vaca F. Gut Microbiota-Derived TMAO.. Int J Mol Sci. 2023;24(3):1940. Published 2023 Jan 18. doi:10.3390/ijms24031940
Monda V, Villano I, Messina A, et al. Exercise Modifies the Gut Microbiota with Positive Health Effects. Oxid Med Cell Longev. 2017;2017:3831972. doi:10.1155/2017/3831972
O'Donnell JA, Zheng T, Meric G, Marques FZ. The gut microbiome. Nat Rev Nephrol. 2023;19(3):153-167. doi:10.1038/s41581-022-00654-0
Ong S, Rose NR, Čiháková D. Natural killer cells in inflammatory heart. Clin Immunol. 2017;175:26-33. doi:10.1016/j.clim.2016.11.010
Velasquez MT, Ramezani A, Manal A, Raj DS. Trimethylamine N-Oxide: The Good, the Bad and the Unknown. Toxins (Basel). 2016;8(11):326. Published 2016 Nov 8. doi:10.3390/toxins8110326
Vourakis M, Mayer G, Rousseau G. The Role of Gut Microbiota on Cholesterol Metabolism. Int J Mol Sci. 2021;22(15):8074. Published 2021 Jul 28. doi:10.3390/ijms22158074
Xia N, Lu Y, Gu M, et al. A Unique Population of Regulatory T Cells in Heart Potentiates Cardiac Protection From Myocardial. Circulation. 2020;142(20):1956-1973. doi:10.1161/CIRCULATIONAHA.120.046789