- Metabolic health can be defined by several clinical markers, including blood pressure, blood sugar, and blood lipid levels.
- This healthy balance of gut microbiota and optimum gut health leads to improved overall well-being, including benefits to our metabolic health.
- Apart from reducing the consumption of sugar and fats, increasing the intake of prebiotics should also be considered to support metabolic health.
Metabolic health can be defined by several clinical markers, including blood pressure, blood sugar, and blood lipid levels. Metabolic syndrome refers to a cluster of biological risk factors that can lead to chronic conditions like diabetes, heart disease and other health problems [1]. It is estimated that more than 3 in 10 adults in the United States suffer from metabolic syndrome [2]. Good metabolic health can help lower your risk of developing such disorders.
Other than lifestyle changes such as engaging in regular exercises, improving sleep and managing stress, dietary changes also help support our metabolic health and processes. Apart from reducing the consumption of sugar and fats, increasing the intake of prebiotics (whether via food or supplements) should also be considered. Read on to understand more about prebiotics and how they help improve and support our metabolic health.
As defined by the International Scientific Association for Probiotics and Prebiotics (ISAPP), a prebiotic is defined as a substrate that is selectively utilized by host microorganisms conferring a health benefit [3].
Our gut consists of trillions of microorganisms including bacteria, viruses, fungi and protozoa species. This composition of microorganisms is termed the gut microbiota and is unique to everyone. It varies due to several factors such as environmental, lifestyle, dietary habits, and consumption of medications such as antibiotics [4]. An optimum gut microbiota consists of a healthy balance of both good and bad gut bacteria species.
Prebiotics feed and enable the proliferation of good gut bacteria, which in turn crowd out the bad ones. This healthy balance of gut microbiota and optimum gut health leads to improved overall well-being, including benefits to our metabolic health.
One aspect of metabolic health is blood cholesterol level. Studies have shown that a healthy balance of gut microbiota may lower blood cholesterol levels through several mechanisms. One mechanism is the metabolizing of cholesterol into coprostanol, which reduces cholesterol absorption [5,6].
Good gut bacteria feed on prebiotics in a process called fermentation, which produces short-chain fatty acids (SCFAs). SCFAs like butyrate and propionate may also have cholesterol-lowering effects by controlling and inhibiting liver cholesterol synthesis [7].
Prebiotics may also have a direct effect on lowering cholesterol levels. Prebiotics, many of which are dietary fibers, move to the colon largely unchanged and undigested. This helps to increase the viscosity of the digestive tract, leading to decreased absorption of cholesterol and blood cholesterol levels [8].
Blood sugar is another aspect of metabolic health. Apart from cholesterol levels, the metabolites of the fermentation process also influence sugar metabolism and homeostasis. SCFAs such as butyrate act as signaling molecules and activate receptors involved in secreting chemicals called glucagon-like peptide 1 (GLP-1). GLP-1 is crucial in blood glucose metabolism by increasing insulin release [9].
SCFAs also directly impact sugar metabolism, by improving glucose metabolism in the liver and increasing sugar uptake by the body cells [9].
For prebiotics which are dietary fibers, they also support healthy blood pressure. The use of fibers to reduce blood pressure has been studied and published in various clinical trials. A meta-analysis has shown that fiber supplementation at 11.5g per day was able to decrease blood pressure [10]. The Dietary Approaches to Stop Hypertension (commonly known as the DASH diet) also recommends a high-fiber intake as one of the many recommendations to reduce blood pressure.
The gut microbiota and SCFAs produced from the fermentation of prebiotics can also affect blood pressure. SCFAs activate receptors that play a part in blood pressure regulation. Unhealthy gut microbiota also leads to chronic low-grade inflammation which can be a cause of high blood pressure as well [11].
Metabolic health disorders are on the rise across the world. Besides lifestyle modifications such as regular physical activity, managing stress and having adequate sleep, dietary modifications also help. Prebiotics enhance the gut microbiota and optimize gut health, which in turn support metabolic health such as blood pressure, sugar and cholesterol levels as shown in various studies.
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- Cardiovascular diseases are the leading causes of death worldwide, taking almost 18 million lives every year
- Optimum gut health means having a right balance of good gut microbes against bad ones in our gut.
- Our gut health is associated with our cardiovascular health in 3 ways.
- Prebiotics could be used to enhance and regulate the health of the gut microbiota, thereby improving gut health and support our cardiovascular health.
Cardiovascular diseases are the leading causes of death worldwide, taking almost 18 million lives every year [1]. 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 [2]:
- High blood pressure (hypertension) - High blood cholesterol - Diabetes - Obesity - Lack of physical activity - Excessive alcohol - Smoking
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 [3].
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 [4] and pressure levels [5], and immune health [6]. 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 [7]. Disruptions in gut microbiota can also lead to excessive accumulation of body fat in early ages [8].
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 [11]. Elevated TMAO levels were shown to accelerate atherosclerosis, which is a significant pathway in the development of cardiovascular diseases [11]. 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 [14].
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 [9]. In heart failure patients, there is often impaired intestinal barrier function due to bowel wall edema, leading to this ‘leaky gut’ hypothesis [9]. 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 [15]. Studies have also shown that heart failure patients have higher endotoxin levels in the bloodstream [16]. Such leaky gut can be improved by improving the health of your gut microbiota, which can be done via taking prebiotics [17].
#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 [18], lipid metabolism [19] and blood sugar homeostasis [20]. 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) [21].
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:
- Metabolic markers: blood pressure, sugar and cholesterol - Immune health - Nervous system - Mental health - Healthy aging - Respiratory health - Skin health
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.
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- Around 1.4 million Americans are diagnosed with diabetes every year.
- Our gut microbiota is associated with blood sugar levels and diabetes, both type 1 and type 2.
- Compositions of the gut bacteria differ in patients with diabetes and those without. The metabolites of the fermentation of prebiotics and dietary fiber by the gut microbiota play a central role in sugar metabolism and homeostasis, thus affecting blood sugar levels.
- Consuming more prebiotics has also been linked with a lower incidence of type 2 diabetes.
Diabetes is an increasingly prevalent metabolic condition, with more than 1 in 10 people in the United States (US) has diabetes, and around 1.4 million Americans are diagnosed every year [1]. This condition has also cost hundreds of billions of dollars in terms of healthcare expenditure [1], and has multiple complications including kidney, heart, stroke, and loss of vision [2]. There are mainly 2 types of diabetes (excluding gestational diabetes, which refers to diabetes that occurs during a woman’s pregnancy) [2]:
- Type 1 diabetes mellitus (T1DM): an autoimmune disease whereby the body produces antibodies to attack the cells that produce insulin. This causes the body to be unable to produce any insulin and hence must rely on daily insulin injections. T1DM is usually diagnosed in younger age patients. - Type 2 diabetes mellitus (T2DM): your body is unable to use insulin efficiently, leading to high levels of blood sugars as they do not react to the insulin. T2DM is usually diagnosed in adulthood.
In recent years, studies have shown the composition of the microorganisms in your gut, also termed as the gut microbiota (or gut microbiome), is implicated with blood sugar control and even diabetes (both Type 1 and Type 2). How are they associated with each other, and does one affect the other? Read on to find out more about the connections between them.
Before we investigate the associations between gut microbiota and blood sugar or diabetes, we first need to understand: what exactly is the gut microbiota? The health of the human digestive system is greatly affected by the composition of the microorganisms that resides within our gut. These may include bacteria, virus and even fungi species. The number of bacterial cells here is estimated to be more than 10 times the number of human cells [3]. Composition and amount of gut microbiota are affected by many factors: environmental, lifestyle, dietary habits, antibiotics consumption, and many more [4].
The gut microbiota is also involved in the fermentation of prebiotics, to form metabolites such as short-chain fatty acids (SCFAs) and butyrate which confers certain health benefits to us. Prebiotics are defined by the International Scientific Association for Probiotics and Prebiotics (ISAPP) as ‘a substrate that is selectively utilized by host microorganisms conferring a health benefit’ [5].
Dysbiosis refers to a change of the composition of gut microbiota due to factors like diet, toxins, drugs, and pathogens [6], and this has been linked with many diseases, such as obesity, diabetes, and certain inflammatory conditions such as inflammatory bowel disease (IBD).
Type 1 diabetes mellitus
The incidence of T1DM is thought to be related to the interactions between both the immune system (innate immunity) and the gut microbiota [7].
In mice studies, the changes in the gut microbiota composition were also associated with development of type 1 diabetes with its effects on the immune system [8]. The Environmental Determinants of Diabetes in the Young (TEDDY) study carried out in humans aimed to identify the microbial composition that are predictive of T1DM and has shown protective effects of SCFAs in early-onset T1DM [9].
Type 2 diabetes mellitus
Research has shown that the composition of the gut microbiota differs in patients with T2DM and non-diabetic adults [10]. Patients with T2DM have a significantly higher proportion of Bacteroides and Proteobacteria than non-diabetic adults, and a significantly lower proportion of Firmicutes species [10]. This ratio was associated with an increased blood sugar levels after glucose load [10].
The metabolites of the fermentation of prebiotics and dietary fiber by the gut microbiota plays a central role in several homeostasis and cell signaling pathways [11]. These species are often found in lower abundance in patients with T2DM [11]. Metabolites such as SCFAs (butyrate and acetate etc.) strongly influence sugar metabolism and homeostasis, including the uptake of glucose by cells and preventing the breakdown of complex components to glucose molecules, all of which helps in reducing blood sugar levels [11].
Another possible explanation of how the gut microbiota affects T2DM could be via inflammation. T2DM as a metabolic condition is also associated with chronic, low levels of inflammation [12]. Different species of gut microorganisms have different effects on inflammation: some having pro-inflammatory effects (such as Fusobacterium), while others have anti-inflammatory properties (such as Akkermansia muciniphila). These anti-inflammatory properties of the good gut microbiota can potentially aid in improving insulin sensitivity, playing a crucial role in T2DM [12].
One of the crucial regulators of the gut microbiota is your diet, with changes shown as rapidly as within 24 hours [7]. Consuming more prebiotics has also been linked with a lower incidence of T2DM [13]. A diet rich in prebiotics has been demonstrated to improve the gut microbiota composition (e.g., butyrate-producing bacterial species), leading to greater HbA1c reduction [14]. Prebiotics enhance the proliferation of good gut bacteria, which in turn will crowd out the bad bacteria. Other than promoting gut microbiota stability, the intake of prebiotics also promotes the fermentation by the gut microbiota (as they are also prebiotics in nature), leading to increased concentration of beneficial SCFAs [7].
The gut microbiota is not only associated with the health of your gut. It also plays a role in the development of many other diseases and body systems, which includes blood sugar levels and diabetes mellitus. Prebiotics’ actions on promoting a healthy gut microbiota also has indirect effects in controlling blood sugar levels, and subsequently diabetes mellitus.
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