Boost your health by supporting your gut-liver axis

Did you know that an estimated 80% of adults with NASH (an advanced form of non-alcoholic fatty liver disease) are undiagnosed? With rates of diagnosis low and instances of liver diseases increasing¹, there’s no better time to start focusing on your liver health than today! The liver plays a significant role in not only your overall health but also your gut health.

The gut microbiome and the liver form the gut-liver axis, a bidirectional pathway communicating through the portal vein and biliary system. Signals are sent from one to the other through metabolites and other compounds, which regulate inflammation, bile secretion, gut microbiota, and more.

The liver plays a vital role in the gut’s functioning, and vice versa! Read on to find out just how important it is –

How are the gut and liver connected?

The gut and the liver are physically connected by the portal vein and the biliary system. The close relationship allows for a bidirectional flow of information and substances, such as bile acids.² Let’s take a closer look at how these work –

The portal vein carries nutrient-rich blood from the intestines, spleen, pancreas and gallbladder into the liver. The liver filters this blood before it leaves and then moves into the heart and enters systemic circulation around the body.³ At any one time, the liver holds about 13% of the body’s total blood volume!⁴

The biliary system is comprised of the bile duct, gallbladder and other relevant structures that are involved with bile acid production and transportation.⁵

Key functions of the gut-liver axis

The liver has over 500 functions alone⁶, but how do these link to the g ut? The close relationship between the organs means they directly influence one another and need to work together to keep both your liver and gut happy and healthy.

Bile production

The liver is responsible for producing bile – it can produce 800-1000ml each day! It is an incredibly important part of the digestive process, as bile is responsible for emulsifying dietary fat and breaking it down so the bloodstream can efficiently absorb any nutrients.⁷

Bile is stored in the gallbladder and is made up of a range of substances like cholesterol, bile salts, water, bilirubin, copper and other metals. Cholesterol in the liver is eliminated from the body through its conversion to bile acids.⁸ Bile is also responsible for transporting bilirubin out of the liver so it can be eliminated through the digestive process.⁹

There are different kinds of bile acids¹⁰¹¹ –

Primary bile acids – These are synthesised in the liver from cholesterol and are conjugated with either taurine or glycine before being secreted to emulsify dietary fat.
Secondary bile acids – These are produced from primary bile acids interacting with intestinal microbiota in the gut.

Bile acids are conjugated in the liver with the amino acids taurine or glycine – these are known as bile salts.¹²

Bile acids also have antimicrobial properties, which can disrupt bacterial membranes and affect gut microbial diversity. A 2022 animal study found that bile acids may inhibit specific pathogens but not others.¹³¹⁴

Besides waste elimination and breaking down dietary fat, bile acids have another important mechanism – bile acid signalling. The bile acids are transported back into the liver after interacting with the gut microbiota, sending signals depending on their composition to the liver regarding lipid metabolism, glucose regulation and inflammation.¹⁵

Nutrient processing

The liver plays a crucial role in processing and distributing nutrients from the intestines. The nutrients are carried to the liver via the portal vein, where they are used by the liver, transformed or distributed to parts of the body.¹⁶

Filtration and detoxification

The liver filters and detoxifies substances from the intestine, which it receives via the portal vein. The liver goes through three detoxification phases – activation or functionalization (phase 1), conjugation (phase 2), and elimination (phase 3).¹⁷

The nutrients extracted from food in the gut play a vital role in supporting all three phases. As mentioned above, the liver uses some of the nutrients received to support its functioning. You can read more about which foods and nutrients support the phases in our article How to support phase 1, 2, and 3 liver cleanse through food.

Toxins that need to be eliminated are filtered through the liver, with water-soluble toxins excreted via urine and fat-soluble toxins through the gut as faeces.¹⁸

Metabolic regulation and function

The liver is responsible for a range of metabolic functions, such as ensuring your blood sugar levels remain stable, regulating lipid metabolism and breaking down amino acids so they can be used as energy.¹⁹ It is also involved in metabolising common medications and drugs such as paracetamol or ibuprofen, where the byproducts are eliminated via the intestines or through urination.²⁰

Immune system balance

The gut-liver axis plays a part in your immune response – your gut houses 70-80% of your immune cells!²¹ Metabolites such as short-chain fatty acids (SCFAs) created in the gut and other microbes modify bile acids. We discussed bile signalling earlier; this mechanism plays a role in modulating immune system response and function. It impacts the immune responses of macrophages, dendritic and natural killer T cells.²²

What happens when the balance is upset?

Gut dysbiosis often plays a key role in disrupting the gut-liver axis. When harmful bacteria outcompete the helpful ones, this can drive intestinal inflammation. Because the microbiota and levels of SCFAs in the gut can shape bile acid composition for better or worse, the altered bile acid signals the liver receives may cause issues with bile acid production and immune system modulation.²³

G ut permeability occurs when the intestinal barrier is compromised, often through inflammation²⁴, allowing metabolites and endotoxins such as lipopolysaccharides (LPS) to pass through the gut barrier, into the blood and liver. This can impair bile acid and drive liver inflammation.²⁵²⁶

It can be a tricky cycle as gut dysbiosis can drive inflammation and alterations to bile acid signalling, fueling gut dysbiosis more and impacting inflammation in the liver. Sustained liver inflammation is an early stage of most liver diseases²⁷, so interrupting the cycle can be important for both your liver and your gut health.

For tips on supporting your liver so it can work at its best, check out our article How to support your liver: your body’s natural filter!

Any questions? Contact one of our Nutritional Therapists via live chat, weekdays 8am to 8pm.