High cholesterol levels are often attributed to diet. However, most cholesterol is produced by the liver. Its journey doesn’t end there, nor does it always enter the bloodstream. Instead, cholesterol and cholesterol-derived bile acids can enter the digestive tract to help emulsify fats.

Once inside the digestive tract, gut bacteria can modify cholesterol via bile acid metabolism, conversion into coprostanol, or short-chain fatty acid production. Gut bacteria, therefore, play a crucial role in cholesterol metabolism.

If there’s any disruption to your gut bacteria, it can affect these processes. That’s why gut microbiome testing is often recommended, as it can show which microorganisms and functional genes are present, although a blood test is needed to measure cholesterol.

How Are Gut Health and Cholesterol Connected?

Cholesterol isn’t automatically bad. It’s needed to build cell membranes, produce hormones, and make bile acids. Problems arise when LDL (“bad”) cholesterol becomes elevated, allowing fatty deposits to accumulate inside arteries.

Because gut bacteria are critical to cholesterol metabolism, they can influence how much is absorbed, produced, recycled, or excreted. There isn’t a single “good” cholesterol-lowering bacterium. It’s a combination of microbial enzymes and metabolites that help regulate levels.

The same bacterial community also appears to influence blood sugar regulation, making the microbiome relevant to several aspects of metabolic health.

Bile Salt Hydrolase Changes How Bile Acids Are Recycled

The liver not only produces cholesterol, but it also converts it into bile acids, which help digest and absorb dietary fat. Most bile acids are normally reabsorbed and returned to the liver.

Some gut bacteria produce bile salt hydrolase (BSH), an enzyme that partially breaks down the bile acids. This prevents them from being absorbed, meaning the liver must convert more cholesterol into bile acids to replace them.

BSH isn’t always beneficial, however. BSH activity also changes bile acid signalling and the production of secondary bile acids. That means it can lower cholesterol levels, but its effect depends on the bacteria and bile acids.

Some Gut Bacteria Convert Cholesterol into Coprostanol

Another method for removing cholesterol from circulation is converting it to the poorly absorbed coprostanol.

Not all people have bacteria that can do this in sufficient volume. However, as one study showed, lower faecal and blood cholesterol is associated with this form of cholesterol-converting bacteria.

Short-Chain Fatty Acids May Affect Cholesterol Production

Gut bacteria ferment fibre to produce short-chain fatty acids. One particular fatty acid, propionate, can influence cholesterol production in the liver and absorption by the intestine.

A small human trial found that propionate supplementation reduces LDL and total cholesterol in people with elevated LDL. It’s not clear if eating more fibre can also help reduce levels, but it’s a reasonable conclusion.

That being said, other SCFAs like acetate can actually be used as a building block for cholesterol under some conditions. So, the picture isn’t completely clear.

Does a Healthier Microbiome Mean Lower Cholesterol?

Not always. There is a definite link between particular microbial functions and cholesterol levels. However, the gut microbiome can contain hundreds of species of bacteria and other microorganisms, complicating the mechanisms.

Plus, there’s genetics, age, diet, body weight, medication, and physical activity to consider. Currently, there isn’t a universally agreed “heart-healthy microbiome” that guarantees lower cholesterol. However, some species do show potentially beneficial effects for cholesterol levels.

How to Support the Gut-Heart Connection

Despite the research not being conclusive, supporting a healthy gut microbiome is definitely worth the effort. Consider these lifestyle changes:

• Eat more soluble fibre from oats, barley, beans, lentils, fruit, and vegetables.

• Include a wide variety of plant foods.

• Replace saturated fats with unsaturated fats where possible.

• Exercise regularly and avoid smoking.

• Increase fibre gradually if it causes bloating or discomfort.

Many of these habits will also benefit heart health in general, so it’s worth adding them to your routine.

What Can a Stool Microbiome Test Tell You?

stool microbiome test can tell you what bacteria are present, how many of them there are, and what effect they could be having on your cholesterol levels.

It’s not a direct prediction of heart health, but it can indicate what you should do to minimise cholesterol levels.

The Functional Gut Clinic is a leading microbiome testing clinic offering a wide range of options. We can help you understand your gut microbiome, recommending specific dietary changes to help boost beneficial bacterial levels.

Learn more about our testing options and take control of your health.

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