Glossary · Nutrition and probiotics
Butyrate
In one sentence
Butyrate is a four-carbon short-chain fatty acid produced by certain colonic bacteria when they ferment fibre. It is the main energy source for colonocytes and contributes to the function of the intestinal barrier.
Also known as: butyric acid · butyrato
What is butyrate?
Butyrate is the ionised form of butyric acid, a four-carbon fatty acid. With acetate and propionate it makes up the main trio of short-chain fatty acids in the colon. It is produced by specific groups of anaerobic bacteria, notably Faecalibacterium, Roseburia and related genera, as they ferment dietary fibre and resistant starch. Some of these bacteria can also make butyrate from lactate or acetate released by other species — a good example of metabolic cross-feeding within the microbiota.
What it is used for in the body
The firmest evidence concerns energy supply. In 1980 Roediger showed (Gut) that, in isolated human colonocytes, butyrate accounted for roughly three-quarters of oxygen consumption when it was the only substrate available. Research has since linked it to other roles:
- Supporting epithelial barrier function, studied in relation to intestinal permeability.
- Modulating local immune responses, for example regulatory T cells (largely in animal models).
- Inhibiting histone deacetylases, which influences gene expression in gut cells.
The review by Mukhopadhya and Louis (Nature Reviews Microbiology, 2025) summarises these mechanisms but stresses that translating them into specific clinical benefits in people needs further study.
How it is measured
Butyrate is quantified in stool by gas chromatography-mass spectrometry (GC-MS), usually together with acetate and propionate. Two points to keep in mind:
- Because the colon absorbs and uses most of its butyrate, the faecal figure is only an indirect reflection of production.
- Recent diet, antibiotics, transit time and how the sample is collected and stored all affect the result. Reference intervals are laboratory-specific.
Example
At a physician’s request, a clinical dietitian reviews a profile in which bacterial composition looks preserved but butyrate is low and acetate within range. The finding steers the conversation towards the amount and type of fibre in the diet. After a few months of guided changes, the clinician decides to repeat the test to see how things have evolved, rather than reading the figure in isolation.
Butyrate at Xenogene
Xenogene’s functional metabolomics test measures butyrate, propionate and acetate by GC-MS in a stool sample and reports their concentrations and relative proportions. Read alongside the gut microbiota analysis, it allows potential butyrate producers to be compared with the butyrate actually present. It is available to healthcare professionals on prescription, and interpretation rests with the requesting clinician.
Frequently asked questions
Which foods contain butyrate?
Butter and some cheeses contain small amounts of butyric acid, but most butyrate in the colon is made by bacteria from fibre. That is why the focus is usually on foods that support its production, such as pulses, oats, wholegrains and resistant starch, rather than foods that supply it.
Do butyrate supplements work?
Sodium butyrate and tributyrin supplements are available, but human trials are few and results are mixed. The evidence is preliminary, and their use is best discussed with a healthcare professional.
Which bacteria produce butyrate?
Well-studied producers include Faecalibacterium prausnitzii, Roseburia, Eubacterium rectale and Anaerobutyricum. Detecting them shows a potential capacity, not how much butyrate is actually being made.
Related terms
- Short-chain fatty acids
Short-chain fatty acids (SCFAs) are fatty acids with one to six carbon atoms produced by colonic bacteria when they ferment fibre and other non-digestible carbohydrates. The main ones are acetate, propionate and butyrate.
- Dietary fibre
Dietary fibre is the group of plant carbohydrates, plus lignin, that the human small intestine cannot digest or absorb. It reaches the colon, where it adds bulk to stools and is partly fermented by the gut microbiota.
- Intestinal permeability
Intestinal permeability is how easily substances in the gut lumen cross the intestinal lining into the bloodstream. It is a normal, regulated property; increased permeability is associated with several diseases.
- Metabolomics
Metabolomics is the large-scale study of metabolites — the small molecules produced by the activity of cells and microorganisms — in a biological sample such as blood, urine or stool. It reflects what is happening in a system at a given moment.
Educational content for healthcare professionals and the general public. It does not replace assessment by a healthcare professional: ordering and interpreting any test is the responsibility of the requesting clinician.
Updated on