In brief
The microbes that live in your gut, most of them in the large intestine. They help break down food, make some vitamins and turn fibre into short-chain fatty acids.
- Eating more foods containing resistant starch is one way to encourage a healthy microbiome, according to the Australian Academy of Science.
- Different probiotics can have different effects, so results for one product do not apply to another.
- Research on gut microbes and the brain is still in its infancy, and most studies have been done in rodents rather than people.
How it works
Estimates put the number of microorganisms in the human gut at between 30 trillion and 400 trillion. They break down foods, make vitamins, and turn resistant starch and fibre into short-chain fatty acids such as acetate, propionate and butyrate. They may also play an important role in training the immune system.
Antibiotics can sharply reduce gut microbe populations. People whose gut bacteria are fewer and less diverse appear more prone to obesity, and a rise in autoimmune disorders has been associated with changes in gut microbes. Much of this evidence comes from animal studies, and cause and effect is not proven.
Myth check
The claim
Probiotic supplements are proven to improve everyone's gut health.
What the evidence says
The Australian Academy of Science says the jury is still out on probiotics, and the US National Center for Complementary and Integrative Health notes that different types of probiotics may have different effects.
Connections
8 connections on the map. Select a topic to read its page.
Gut microbiome is linked with
- Gut microbe imbalance (dysbiosis) Emerging
Imbalances in gut bacteria have been linked to a number of health problems, including obesity, mood disorders and altered immune responses.
Source: Australian Academy of Science, Gut bacteria: the inside story
- Gut-brain axis Emerging
Research on gut microbes and the brain is still in its infancy, and most studies have been done in rodents rather than people.
Source: Australian Academy of Science, Gut bacteria: the inside story
- Probiotics Emerging
Probiotics are live microorganisms intended to have health benefits, and different types can have different effects.
Sources: NIH NCCIH, Probiotics: what you need to know; NIH Office of Dietary Supplements, Probiotics fact sheet for consumers
Gut microbiome is supported by
- Dietary fibre (including prebiotics) Supported
Gut bacteria ferment fibre such as resistant starch into short-chain fatty acids.
Sources: Better Health Channel (Victorian Government), Fibre in food; Australian Academy of Science, Gut bacteria: the inside story
- Healthy eating pattern Supported
Eating more foods containing resistant starch is one way to encourage a healthy microbiome.
Source: Australian Academy of Science, Gut bacteria: the inside story
Gut microbiome is part of
A large reservoir of microbes, such as bacteria, lives within the large intestine.
Source: Better Health Channel (Victorian Government), Digestive system explained
Gut microbiome is needed for
Gut microbes turn resistant starch and fibre into short-chain fatty acids such as acetate, propionate and butyrate.
Sources: Australian Academy of Science, Gut bacteria: the inside story; Better Health Channel (Victorian Government), Fibre in food
Gut microbiome supports
- Immune tolerance Emerging
Gut microbes may have an important role in training the immune system.
Source: Australian Academy of Science, Gut bacteria: the inside story
Medicines and supplements
General education only. Never start, stop or change a medicine without your prescriber.
Sources
- Gut bacteria: the inside story
- Digestive system explained
- Fibre in food
- Probiotics: what you need to know
Each connection above names its own source. See every source AskBioMap uses.
Summarised from the Australian Academy of Science, the Better Health Channel and the NIH. Sources read on 13 October 2026. General education only, not medical advice. Spotted a mistake? Please tell us through the HuBu-Intel contact page.