An easy-to-understand guide to the portal vein, bile acids, the microbiome and the two-way conversation between digestion and metabolism.

The gut and liver are often described as separate organs with separate jobs. Anatomically, however, they are close working partners. Most substances absorbed from the stomach and intestines do not enter the general circulation first. They travel through the hepatic portal vein directly to the liver.

That gives the liver an unusual position: it is the first major processing and inspection centre downstream from digestion. Nutrients, medications, microbial metabolites and small amounts of microbial material arriving from the intestine all meet liver cells, blood-vessel lining cells and immune cells before much of that portal blood rejoins the wider circulation.

Communication also travels in the other direction. The liver makes bile, which enters the intestine to help digest fats. Gut microbes then modify some bile acids, creating signals that can influence metabolism and microbial ecology. This continual exchange is known as the gut–liver axis.

 

What Is the Gut–Liver Axis?

The gut–liver axis is the bidirectional relationship among the digestive tract, intestinal barrier, gut microbiome, portal circulation, liver and biliary system. It is not a single tube or hormone. It is a network of physical routes and biological messages.

 

 

The Portal Vein: A Direct Line From Gut to Liver

After digestion, blood from much of the stomach, small intestine and large intestine converges into the portal circulation. The liver receives roughly three-quarters of its blood supply from the portal vein, although this blood carries less oxygen than arterial blood. It flows through specialised channels called sinusoids, where hepatocytes and immune cells sample and process its contents.

Not everything absorbed follows this route. Most long-chain dietary fats are packaged into chylomicrons and initially travel through intestinal lymphatic vessels before entering the bloodstream. This exception is a useful reminder that human biology rarely fits a single rule.

To follow food through digestion and absorption, read The Complete Guide to Healthy Digestion: How Your Body Breaks Down Food, Absorbs Nutrients & Supports Whole-Body Health.

What the Liver Does With What Arrives

The liver is not simply a filter. It is a metabolically active organ that decides, transforms, stores, releases and packages. Its functions include:

·       Converting and storing glucose as glycogen

·       Processing amino acids and safely handling nitrogen

·       Making and exporting lipoproteins

·       Producing bile

·       Storing iron and several vitamins

·       Making albumin and many blood-clotting proteins

·       Transforming hormones, medications and other compounds

·       Supporting immune surveillance through resident cells

 

Bile: Digestion and Chemical Communication

Bile is made in the liver and stored in the gallbladder between meals. When fat enters the small intestine, bile acids help disperse fat into smaller droplets so digestive enzymes can work efficiently and fat-soluble vitamins can be absorbed.

Most bile acids are then reabsorbed and returned to the liver. Gut microbes transform a portion into secondary bile acids. These molecules do more than digest fat: they can bind receptors involved in glucose, lipid and energy metabolism. In this sense, bile is both a digestive fluid and part of the communication system linking liver, intestine and microbiome.

The Intestinal Barrier: Selective, Not Sealed

The intestinal barrier must solve a difficult problem. It needs to absorb nutrients and water while limiting the passage of intact microbes and potentially harmful material. Mucus, epithelial cells, tight junctions, immune tissue and the gut vascular barrier all contribute.

A healthy barrier is not completely impermeable. It is selective and responsive. When regulation is disrupted, greater exposure to microbial products can affect immune signalling in the liver. Much of the detailed disease mechanism comes from experimental and clinical research in specific liver conditions, so it should not be used to diagnose everyday digestive symptoms.

For a careful explanation of permeability, see Leaky Gut, Intestinal Permeability & Gut Barrier Function: The Complete Guide.

The Microbiome at the Interface

Gut microbes transform dietary fibre, resistant starch, proteins, bile acids and other compounds into a wide range of metabolites. Short-chain fatty acids can nourish colon cells and participate in immune and metabolic signalling. Other microbial products may be neutral, useful or challenging depending on concentration, location and the health of the host.

This is why “good bacteria” and “bad bacteria” is too simple. Function depends on the community, the available food, the intestinal environment and what the liver does with the resulting compounds.

Dietary variety helps provide a wider range of substrates for this ecosystem. Read Microbiome Diversity Explained: Why Variety Is One of the Best Things You Can Feed Your Gut.

What About the Liver’s “Detox” Pathways?

The liver continually transforms substances made inside the body and encountered through food, medicines and the environment. Scientists often group many biotransformation reactions into Phase I, Phase II and transport or Phase III processes.

 

These are useful categories, not a conveyor belt that every compound follows in order. A substance may undergo Phase II directly, move through several reactions, become active rather than inactive, or be handled in tissues beyond the liver. Food does not “switch on detox” in a simple way, and aggressive cleanses are unnecessary.

Glutathione participates in some conjugation and antioxidant systems. Optimising Glutathione Naturally: How Food Supports the Body’s Antioxidant Defences explains how the body makes and recycles it.

Protein and Amino Acids: Necessary, but Not a Detox Prescription

Amino acids are required to build liver enzymes, transporters, plasma proteins and antioxidant-related molecules. Glycine, cysteine and glutamate are used to make glutathione, while glycine and taurine are also used in bile-acid conjugation. This does not mean one amino acid cleanses the liver. The body draws from the wider amino-acid pool and regulates these pathways according to need.

A varied diet should include adequate complete protein as well as other foods. For the foundations, read Amino Acids The Building Blocks and Functional Proteins Explained: Why Whey, Collagen & Bone Broth All Have Different Roles.

Food Patterns That Support the Wider System

No “liver food” can compensate for an overall pattern dominated by excess alcohol, inadequate fibre or chronic energy imbalance. The strongest foundations support the gut, liver, blood vessels, muscles and metabolism together.

·       Eat vegetables, fruit, legumes, nuts, seeds and whole grains where suitable

·       Include enough protein from a variety of animal or plant foods

·       Choose unsaturated fats such as extra-virgin olive oil, nuts, seeds and fish

·       Limit alcohol or avoid it

·       Keep ultra-processed foods as a smaller part of the overall pattern

·       Move regularly and include resistance exercise

·       Support sleep and regular meal patterns

·       Use medicines and supplements as directed; “natural” does not automatically mean liver-safe

 

Where Bone Broth Fits

Bone broth does not detoxify the liver. It can be used as a warm savoury fluid and a practical ingredient in balanced meals. Broth & Co Bone Broth Powder provides approximately 5 g of naturally occurring protein per prepared serve, including collagen-derived amino acids.

Its most useful role is culinary: it can add flavour and fluid to soups, grains, legumes, sauces and vegetable-rich meals. Pair it with whole foods and complete protein sources rather than treating it as a standalone gut–liver intervention.

For more context, read Bone Broth Benefits: The Complete Guide to Gut Health, Protein, Recovery & Healthy Ageing.

What the Broth & Co Clinical Study Can—and Cannot—Tell Us

The Broth & Co study examined daily bone broth powder use for eight weeks in Australian adults reporting lower gastrointestinal disturbances. It assessed participant-reported digestive outcomes and a lactulose–mannitol measure used in intestinal-permeability research.

The study did not test liver enzymes, liver fat, bile acids or treatment of liver disease. It is therefore relevant to the digestive and barrier side of this article, not evidence that bone broth improves liver function.

Read the study design and findings in Bone Broth Clinical Study: Digestive Wellbeing & Intestinal Permeability Research | Broth & Co.

Three Gut–Liver-Friendly Recipes

Chicken, Vegetable & Bone Broth Soup

Serves 4

Ingredients

·       1 tablespoon extra-virgin olive oil

·       1 small brown onion, diced

·       1 carrot, diced

·       1 celery stalk, diced

·       1 medium zucchini, diced

·       2 garlic cloves, finely chopped

·       4 cups (1 litre) prepared Broth & Co Bone Broth

·       300 g cooked chicken, shredded

·       1 cup (30 g) baby spinach

·       2 tablespoons chopped parsley

·       1 tablespoon lemon juice

·       Black pepper, to taste

Method

1. Heat the olive oil in a large saucepan over medium heat. Cook the onion, carrot and celery for 5 minutes.

2. Add the zucchini and garlic and cook for 2 minutes.

3. Pour in the bone broth, bring to a gentle simmer and cook for 10 minutes.

4. Add the chicken and spinach and cook for 3 minutes, until hot and the spinach has wilted.

5. Stir through the parsley and lemon juice, season with pepper and serve.

Roasted Pumpkin, Chickpea & Chicken Nourish Bowl

Serves 2

Ingredients

·       2 cups (300 g) pumpkin, cut into 2 cm cubes

·       1 tablespoon extra-virgin olive oil, divided

·       1/2 teaspoon ground cumin

·       1 x 400 g can chickpeas, drained and rinsed

·       200 g cooked chicken, sliced

·       3 cups mixed leafy greens

·       1/2 cup cooked quinoa

·       1/4 cup chopped parsley

·       2 tablespoons pumpkin seeds

·       1 tablespoon lemon juice

·       1 teaspoon Dijon mustard

Method

1. Heat the oven to 200°C (180°C fan-forced).

2. Toss the pumpkin with half the olive oil and cumin. Roast for 25 minutes, turning once, until tender and golden.

3. Whisk the remaining olive oil with the lemon juice and mustard.

4. Divide the greens and quinoa between two bowls. Add the roasted pumpkin, chickpeas and chicken.

5. Spoon over the dressing and finish with parsley and pumpkin seeds.

Apple, Oat & Berry Yoghurt Bowl

Serves 1

Ingredients

·       3/4 cup (170 g) plain Greek yoghurt

·       1/3 cup rolled oats

·       1/2 small apple, grated

·       1/2 cup mixed berries

·       1 tablespoon ground flaxseed

·       1 tablespoon chopped walnuts

·       1/4 teaspoon cinnamon

·       1–2 tablespoons milk, if needed

Method

1. Place the yoghurt, oats, grated apple, flaxseed and cinnamon in a bowl.

2. Stir in enough milk to reach your preferred consistency.

3. Top with the berries and walnuts.

4. Serve immediately, or refrigerate overnight for softer oats.

For more meal ideas, explore the collection of nourishing recipes.

The Gut–Liver Axis Across Life

Children and Adolescents

Growth requires energy, protein, essential fats, vitamins and minerals. Family meals, dietary variety, active play and avoiding unnecessary supplements provide a stronger foundation than adult-style detox trends.

Adults

Work patterns, alcohol, medication use, sleep, activity and body composition can all influence metabolic and digestive health. Routine movement and balanced meals matter before symptoms appear, not only later in life.

Older Adults

Appetite, muscle mass, medication use and nutrient intake may change with age. Adequate protein, fibre, fluids and strength-preserving activity remain important, but sudden weight loss, jaundice, persistent digestive change or loss of appetite deserves medical review.

When to Seek Medical Advice

Digestive discomfort is common and does not automatically indicate liver disease. Seek medical advice for jaundice, dark urine with pale stools, vomiting blood, black stools, severe or persistent abdominal pain, abdominal swelling, unexplained weight loss, ongoing bowel changes or concern about alcohol, medicines or supplements. Liver disease can also be silent, so recommended check-ups and blood tests matter.

A Simple Gut–Liver-Supportive Day

Morning

·       Begin with water, tea or another suitable fluid.

·       Include protein and fibre at breakfast where possible.

·       Use daylight and movement to establish an active day.

During the Day

·       Build meals around vegetables, legumes or whole grains, protein and unsaturated fats.

·       Break up long sitting periods with comfortable movement.

·       Drink according to thirst, weather and activity; keep alcohol limited or absent.

Evening

·       Choose a satisfying meal rather than relying on grazing.

·       Use herbs, spices and citrus for flavour and variety.

·       Protect sleep with a consistent wind-down routine.

Frequently Asked Questions

What is the gut–liver axis?

It is the two-way relationship linking the intestine, microbiome, portal circulation, liver and biliary system.

Does everything absorbed from the gut go straight to the liver?

Many nutrients and compounds travel through portal blood to the liver first. Most long-chain fats initially enter lymphatic vessels before reaching the bloodstream.

What do bile acids do?

They help digest and absorb fats and fat-soluble vitamins. They are also recycled between gut and liver and act as metabolic signals.

Can food detox the liver?

No single food or cleanse detoxifies the liver. The liver already transforms and helps eliminate compounds. A varied dietary pattern, movement, limited alcohol and appropriate medical care support overall health.

Does protein support liver function?

Protein supplies amino acids used throughout liver metabolism, but more is not always better and requirements vary. People with diagnosed liver disease should follow individual clinical advice.

Does bone broth improve liver function?

There is no evidence that bone broth directly improves liver function. It can contribute fluid and collagen-rich protein within balanced meals.

What did the Broth & Co study measure?

It assessed digestive wellbeing and a lactulose–mannitol measure used in intestinal-permeability research. It did not test liver function or liver disease.

Continue Exploring

·       The Complete Guide to Healthy Digestion: How Your Body Breaks Down Food, Absorbs Nutrients & Supports Whole-Body Health

·       Leaky Gut, Intestinal Permeability & Gut Barrier Function: The Complete Guide

·       Microbiome Diversity Explained: Why Variety Is One of the Best Things You Can Feed Your Gut

·       Optimising Glutathione Naturally: How Food Supports the Body’s Antioxidant Defences

·       Food Diversity Explained: Why Variety Matters

References and Further Reading

·       Gut–liver axis: barriers and functional circuits

·       The gut–liver axis and gut microbiota in health and liver disease

·       The gut–liver axis and the intersection with the microbiome

·       Biochemistry of biotransformation

Final Thoughts

The gut and liver are not neighbouring departments working in isolation. They are partners connected by a direct delivery route, a returning stream of bile and a constant exchange of nutrients, microbial metabolites and immune signals.

That connection does not call for a cleanse. It calls for conditions the whole system can work with: varied food, enough fibre and protein, regular movement, limited alcohol, appropriate sleep and medical care when needed. The memorable lesson is simple: what happens after digestion does not stay in the gut. The liver is already listening.