Cardiovascular diseases are the leading causes of death worldwide, taking almost 18 million lives every year . This group of diseases is comprised of conditions affecting the heart and blood vessels, including coronary heart disease, heart attack, and stroke being the more common ones. Some of the risk factors for developing heart diseases are :
Lifestyle changes such as diet modifications and increasing physical activities are ways to lower our risks of developing heart diseases. Here we explore how our gut health and microbiota affect our cardiovascular system.
Optimum gut health means having a right balance of good gut microbes against bad ones in our gut. This composition of microorganisms in our gut is collectively termed as gut microbiota. Our gut consists of trillions of such microorganisms, including bacteria, virus, fungi and protozoa species. This set of gut microbiota is unique to everyone and varies due to several factors including environmental, lifestyle, dietary habits, and consumption of medications such as antibiotics .
The good gut bacteria feeds on prebiotics, leading to the production of metabolites such as short-chain fatty acids (SCFAs)which confer health benefits to us. These benefits include healthy blood sugar  and pressure levels , and immune health . The growth of good gut bacteria will in turn crowd out the bad ones, leading to a healthy balance of gut microbiota and optimum gut health.
This innate set of gut microbiota (the set that we are born with) is thought to be the most optimum for oneself, and this composition and amount of good gut bacteria decrease as we age, along with modern-day diets lacking in prebiotics (food for the good gut bacteria) and increased consumption of medications such as antibiotics.
Although anatomically distinct, our gut is intrinsically linked to our heart. Dysbiosis, which refers to the alteration of the gut microbiota balance, has been reported in patients with risk factors for cardiovascular diseases, such as hypertension . Disruptions in gut microbiota can also lead to excessive accumulation of body fat in early ages .
Here are 3 ways the health of our gut affects cardiovascular health and the various cardiovascular diseases [9,10].
#1: Production of TMAO and its adverse effects on cardiovascular health
Trimethylamine N-oxide (TMAO) has been found to be associated with an elevated risk of cardiovascular diseases, as shown by research done by Wang et al. in 2011, published in the Nature journal . Elevated TMAO levels were shown to accelerate atherosclerosis, which is a significant pathway in the development of cardiovascular diseases . Other studies across the US and Europe have also generated similar results with regards to TMAO and its potential to increase cardiovascular disease risks [12,13]. Other than atherosclerosis, TMAO is also a strong predictor of clinical outcomes in patients with heart failure .
TMAO is produced mainly via a multistep pathway with the gut microbiota as the starting point. Our gut microbiota metabolizes certain types of nutrients including choline, phosphatidylcholine and carnitine into a compound called trimethylamine (TMA). This process is carried out by an enzyme called TMA lyase, which is encoded by certain type of gut microbial genes. TMA is subsequently oxidized into TMAO by certain types of liver enzymes. The precursors of TMAO (choline, phosphatidylcholine and carnitine) are mainly found in red meats, egg yolk and other meat products. Altered gut microbiota can result in an increase in the production of such toxic metabolites such as TMAO.
#2: Leaky gut hypothesis
In a healthy and normal state, there are mechanisms to ensure intestinal barrier function, including tight junctions, mucus production and immunity . In heart failure patients, there is often impaired intestinal barrier function due to bowel wall edema, leading to this ‘leaky gut’ hypothesis . This leaky gut will lead to gut bacteria and other bacterial products into the bloodstream, which can result in pro-inflammatory states for the body. This is usually correlated with heart failure symptom severity and poorer outcomes . Studies have also shown that heart failure patients have higher endotoxin levels in the bloodstream . Such leaky gut can be improved by improving the health of your gut microbiota, which can be done via taking prebiotics .
#3: Effects of SCFAs
SCFAs are produced from the fermentation of prebiotics by the gut microbiota. These metabolites include butyrate, propionate, and acetate. SCFAs have been shown to modulate several risk factors involve in cardiovascular diseases, such as blood pressure , lipid metabolism  and blood sugar homeostasis . By modulating and reducing these blood markers, risk of developing cardiovascular diseases can be reduced. Recent studies have also suggested that SCFAs directly influence cardiac activities, such as repair of heart tissues after injury (such as heart attacks) .
One way to improve our gut health and gut microbiota composition is to take more prebiotics. Prebiotics act as food for the beneficial gut bacteria allowing them to grow and crowd out the harmful ones. By optimizing the balance of our gut microbiota, we improve our gut health which in turn support our cardiovascular system, through less production of toxic metabolites such as TMAO and increase production of beneficial ones such as SCFAs.
Restricting the types of food that give rise to TMAO may also be another lifestyle intervention that can help reduce risk of cardiovascular disease. Reducing intake of red meat can reduce our dietary carnitine and choline, thereby reducing TMAO levels as well.
Other than the benefits on cardiovascular health, optimum gut health can also support the health of other body functions and systems, such as:
Cardiovascular diseases such as coronary heart disease, heart attacks and stroke are some of the most common diseases and causes of death worldwide, and cost billions of dollars in healthcare expenditure. Besides reducing your risks through lifestyle modifications, you can also consider optimizing your gut health. Taking prebiotics enhances the beneficial gut microbiota, which in turn helps improve gut health leading to reduction in risks of cardiovascular diseases.