What is the microbiome?

The microbiome is a collection of many millions of different microorganisms naturally living in and outside of your body. This includes bacteria, fungi, yeasts and viruses.

Different areas of your body have their own microbiomes. For example, you have microbiomes in your:

• gastrointestinal tract (your 'gut')
• respiratory tract
• surface of your skin
• mouth

Your microbiome is unique and always evolving. When your microbiome is healthy, there is a balance of 'good' and 'bad' microorganisms living together. You benefit from these microorganisms, and the microorganisms benefit from you.

Sometimes the balance of 'good' and 'bad' organisms in your gut microbiome can be disturbed. Any change in your microbiome can negatively affect your physical and mental health.

Your largest microbiome is in your gastrointestinal tract. This is known as your gut microbiome. Most of your gut microbiome is in your colon. Your stomach and small intestines have only a few organisms living there because the environment is more acidic.

Why is the gut microbiome important?

Your gut microbiome is important for your physical and mental health:

• Making important nutrients — B group vitamins, vitamin K, essential amino acids and some fats are a source of energy for bacteria in your microbiome.
• Digestion — they digest some sugars your body cannot breakdown.
• Immune system — your gut microbiome supports your immune system in many ways. For example, it acts as a barrier protecting your body against toxins and organisms that cause disease.
• Communicating with your brain — the microbiome communicates with your central nervous system (CNS) which can impact your mental health.

What factors can affect my gut microbiome?

When you are born, there are many things that influence what type of gut microbiome you will develop. Factors include your genetics, the health of your parents, whether you were born via a caesarean section or vaginally, or whether you were breast fed or bottle fed.

In your first year of life, the gut microbiome is influenced by other factors too, such as diet, feeding habits and the surrounding environment. It is thought that the gut microbiome matures between the ages of 1 and 3 years, and becomes stable after that.

Your gut microbiome can also be affected by:

• eating unhealthy foods
• your stress levels
• hormonal changes
• antibiotics
• illness
• your age and genetics

An imbalance in your microbiome is called dysbiosis. When you have dysbiosis, your microbiome cannot properly protect you.

What happens if I have an unhealthy gut microbiome?

An unhealthy gut microbiome impacts your physical and mental health, and is associated with these conditions:

• liver disease, heart disease, arthritis, asthma
• some neurological (nerve) conditions
• some cancers
• inflammatory bowel disease (IBD), inflammatory bowel syndrome (IBS)
• infections
• anxiety, depression

Your gut microbiome is only one of many different factors linked with the development of these conditions. More research is needed to understand the connections between these conditions and your gut microbiome.

Sometimes, a faecal microbial transplant (FMT) may be needed to improve the health of your gut microbiome. More information about FMT is available from the University of New South Wales' Microbiome Research Centre.

How can I keep my gut microbiome healthy?

You can improve the health of your gut microbiome by:

• eating a healthy balanced diet that includes a range of prebiotics
• keeping a healthy lifestyle
• asking your doctor or dietitian to recommend a probiotic supplement

When should I see my doctor?

You should see your doctor if you are experiencing symptoms of pain or discomfort in your stomach, nausea or diarrhoea that won't go away. If you already have a prescription, referral or treatment and your condition has not improved, visit your doctor again.

The Symptom Checker guides you to the next appropriate healthcare steps, whether it’s self-care, talking to a health professional, going to a hospital or calling triple zero (000).

You can also speak to your doctor for guidance if you are interested in taking probiotics, making lifestyle changes, managing a health condition that is affected by dysbiosis, or are worried about your gut health.

ASK YOUR DOCTOR — Preparing for an appointment? Use the Question Builder for general tips on what to ask your GP or specialist.

Resources and support

Queensland Health has an article about the link between your gut microbiome and your mental health.

The CSIRO has information on the latest research findings on the human gut microbiome, and their links to long-term health.

Visit Nutrition Australia for information about the gut microbiome and tips for maintaining gut health.

Listen to the Queensland Health podcast 'My amazing body' to learn more about your gut microbiome.

The Migrant Resource Centre in Tasmania has created a fact sheet on how food can affect your mood, available in several languages.