Key Points:

– It is estimated that about 12% of American adults have high cholesterol levels. 

– There are 2 main ways in which cholesterol can be obtained: exogenous and endogenous.

– Our gut microbiota may be able to alter blood cholesterol levels through several mechanisms.

– Several studies have also shown that prebiotics (which are selectively utilized by the beneficial gut bacteria) are able to lower cholesterol levels via several mechanisms.

Cholesterol is a key component in many cellular structures such as the cell membranes and a precursor to hormones such as steroids in the body. It is widely understood that high levels of it (i.e., hypercholesterolemia) are linked to atherosclerosis (i.e., building up of plagues in the blood vessels) [1] and cardiovascular diseases such as heart attacks and strokes [2]. It is estimated that about 12% of American adults have high cholesterol levels [3].

Cholesterol in the human body is being carried through the blood by proteins called lipoproteins. These proteins can be generally classified into 2 types [4]:

– High-Density Lipoprotein cholesterol (HDLc) (the ‘good’ cholesterol)
– Low-Density Lipoprotein cholesterol (LDLc) (the ‘bad’ cholesterol)

There are 2 main ways in which cholesterol can be obtained [5]:

– Exogenous: dietary uptake, which accounts for about a quarter of total cholesterol
– Endogenous: produced within the body by the liver

The health of our gut is largely dependent on the health of our gut microbiota, which is the unique collection of microbes residing in our gut. Recent studies have shown that the health of our gut is linked to cholesterol levels. Find out more about their associations and what can be done to improve our gut health and gut microbiota.

What is the gut microbiota?

Our gut consists of trillions of microorganisms (or microbes), termed as the gut microbiota. These microorganisms can be bacteria, virus, and fungi. This set of microorganisms in our gut is unique to everyone, depending on several factors such as environmental, lifestyle, dietary habits, and antibiotics consumption [6]. This set of microbes feed on prebiotics to form metabolites such as short-chain fatty acids (SCFAs) and butyrate which confers health benefits to us, which include healthy blood sugar [7], blood pressure [8], immune health [9], and many more.

The innate set of gut microbiota 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 (i.e., food for the good gut bacteria) and increased consumption of antibiotics.

The role of gut microbiota in controlling cholesterol levels

Studies have shown that the gut microbiota may be able to alter blood cholesterol levels, through their role in bile acid metabolism. Both sources of cholesterol pass through the gut, which implies that the gut microbiota may have effects on its levels [10].

Previous research in mice have shown that gut bacteria is able to metabolize cholesterol into a compound called coprostanol, which can aid in reducing cholesterol absorption and blood cholesterol levels [11]. This has also been reflected in recent human studies, which showed that subjects with coprostanol-forming microbes have lower blood cholesterol levels [12].

Another study done in mice also had similar results. Investigators wiped out the gut microbiota of mice using several antibiotics, and they found out that blood cholesterol level was 55% higher than mice who did not had their gut microbiota wiped out [13]. The authors concluded that this phenomenon occurred due to the gut microbiota influencing cholesterol homeostasis and metabolism, including synthesis by the liver [13].

SCFAs are also produced by the gut microbiota because of fermentation of prebiotics (e.g., resistant starch, dietary fibers). High SCFA concentration in the colon can impact microbial communities, inhibiting growth of bad bacteria (such as Salmonella) and promoting growth of beneficial bacteria (such as Lactobacilli and Bifidobacteria), which have been known to reduce risk of cardiovascular diseases [5]. Such SCFAs including propionate and butyrate also have the potential to lower cholesterol synthesis, hence reducing levels in the blood [14].

Evidence of Prebiotics lowering cholesterol

Prebiotic has been officially 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’ [15]. In simple terms, they are food for the beneficial gut bacteria, as they are resistant to digestion from the body’s enzymes and travel down to the colon largely intact.

Several studies have also shown that prebiotics such as inulin are able to reduce the formation of atherosclerotic plagues in mice [16]. It has also been theorized that prebiotics are able to lower cholesterol levels via 2 mechanisms [17]:

– Decreasing cholesterol absorption and increasing excretion
– Indirect effect: producing SCFAs by the gut microbiota, resulting in positive effects on cholesterol metabolism (as described above)

What can be done to help lower our cholesterol?

Although there are medications like statins to lower cholesterol, it is important to also use non-pharmacological methods to maximize outcomes. Other than the usual ways of adopting healthy habits such as engaging in physical activity and losing weight, improving our gut health to promote the growth of beneficial gut bacteria may be another viable way.

Prebiotics encourage the healthy balance of your unique set of resident gut microbiota, creating an environment whereby beneficial bacteria flourish and crowd out unwanted bacteria. This can help in 2 ways:

– Growth of innate healthy and beneficial gut bacteria
– Enhances effects of probiotics supplements, by allowing the beneficial strains to feed on them and increase their chances of survival and proliferate in the colon

Take foods that are rich in prebiotics, including onions, garlics, and wholegrains. If your diet is consistently lacking in such foods, you may also consider adding prebiotic supplements to your food and/or beverages to obtain your daily requirement of prebiotics.

Conclusion

Although high cholesterol does not show any symptoms on its own, it is a huge risk factor for cardiovascular conditions like heart attacks and stroke, which accounts for one of the highest causes of disease and death in many parts of the world. The health of your gut and gut microbiota has been shown to be associated with lower levels of blood cholesterol. One way to improve the health of your gut microbiota is through prebiotics, which encourages the healthy balance of our microbes in our gut.

Related Articles

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Prebiotic: Gut Microbiota, Gut Health, and Beyond

What is the Gut Microbiota?

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