Butyric acid

Butyric acid (butanoic acid, 4:0, C4H8O2) is one of the shortest fatty acids found in food. It is a saturated fat with only four carbons. FAO and WHO (the UN food and health agencies) class fatty acids with three to seven carbons as short-chain. Its salts and esters are called butyrates, and the name comes from the Greek word for butter.

Two sources matter, and they are very different. Bacteria in your colon make most of it by fermenting fiber and resistant starch (starch your small intestine does not digest). A little comes in dairy fat such as butter and milk. Caproic acid (6:0) is its next short-chain neighbor.

Colon cells are the main customers. In cells taken from human colons, butyrate supplied 73% to 75% of their oxygen use when it was the only fuel on offer. Colon cells from germ-free mice, which have no gut bacteria, were short of energy until butyrate was added. That is why butyrate is studied in bowel disease.

The pure acid is better known for its smell. PubChem, a US chemical database, describes a penetrating, rancid odor. A food-science team describes the cheesy, fecal aroma and bitter taste of its ester, tributyrin. That is why supplements use salts or coated forms.

The evidence is narrower than the interest. In a review of 8 trials, butyrate enemas did not clearly beat placebo (a dummy treatment) in ulcerative colitis, an inflammatory bowel disease. Oral butyrate gave mixed results in bowel disease. Small trials point to some relief in irritable bowel syndrome and in weight and blood fats.

A cup of semi-skimmed milk holds 0.19 g of butyric acid in our USDA ranking. The doses in trials came to between 0.12 g and 3.2 g a day of butyric acid (our arithmetic).

Health benefits of butyric acid (butyrate)

• ★★Mixed results in ulcerative colitisButyrate enemas did not clearly beat placebo in 8 trials (227 people). In 98 adults, microencapsulated sodium butyrate (2 × 300 mg a day) gave clinical improvement in 51%, against 21.3% on placebo.
• ★★Mixed results in children with bowel diseaseIn 72 children with Crohn’s disease or ulcerative colitis, sodium butyrate did not raise remission at 12 weeks. A trial in 88 children found 81.82% in remission on butyrate, against 47.73% on placebo.
• ★★Potato resistant starch raised stool butyrateIn 174 young adults, two weeks of potato resistant starch gave the largest rise in short-chain fatty acids, including butyrate. Maize starch and inulin did not clearly raise stool butyrate.
• ★★Butter raised “bad” LDL more than olive oilIn 91 adults, 50 g of butter a day raised LDL by 0.42 mmol/L more than coconut oil and 0.38 more than olive oil. This 4-week test used whole butter, not butyric acid alone.
• ★Mixed results for irritable bowel syndromeIn 66 people with IBS, microencapsulated sodium butyrate eased pain on passing stool, but overall symptom severity was not clearly reduced. In 51 children, 73% on calcium butyrate had at least a 50% drop in their pain score, against 3.8% on placebo (a single small trial).

Foods high in butyric acid (butyrate)

Foods supply butyric acid in two very different ways. The first is dairy fat. In our USDA ranking per serving, semi-skimmed cow’s milk leads with 0.19 g in a cup (246 g). It is far ahead of eggs at 0.002 g in one large egg and a chicken drumstick at 0.001 g.

The order is the same per 100 g and per 100 kcal, as the ranking below shows. Only these three foods carry a value in our data, so butter, cheese and yogurt are not in the ranking.

PubChem lists butyric acid as present in butter as an ester to the extent of 4 to 5%. A review says about one third of all milk triglycerides (fat molecules) hold one molecule of it. FAO and WHO list dairy fat as its typical source.

The second way is indirect. Fiber, resistant starch and inulin (a plant fiber) that reach the colon feed the bacteria that make butyrate. Trials show that fibers differ in how much butyrate they yield.

Resistant starch from potatoes raised fecal (stool) butyrate most in 174 healthy adults, while maize starch and inulin did not. One potato side dish a day did not change fecal butyrate in 50 adults. A diet rich in arabinoxylan (a cereal fiber) and resistant starch did raise it in 19 adults with metabolic syndrome.

Fiber is the bottleneck for most people. A review of national surveys says only about 5% of the US population meets fiber recommendations. The FDA Daily Value (the reference amount on US food labels) for dietary fiber is 28 g.

Compare realistic amounts (our arithmetic). A cup of milk gives 0.19 g of butyric acid. A tracer-model study estimated that gut bacteria make about 1.8 g a day in older adults and 3.6 g in young adults. Dairy fat is a minor source and fiber is the major lever, as the chart below shows.

How butyric acid (butyrate) works

Most of the biology of butyrate comes from cells, mice and a few human physiology studies. What extra butyrate does for people is tested in the study cards above.

Five ideas cover it. Gut bacteria make it, colon cells take up most of it, and it is their main fuel. It also quiets inflammatory signals, and cancer cells treat it differently. Dairy fat carries a little of its own.

Here is each idea, and what has been seen in people.

Gut bacteria make it from fiber

Starch and fiber that escape digestion in the small intestine reach the colon. There, bacteria ferment them to short-chain fatty acids (SCFAs), mainly acetate, propionate and butyrate, says a review of resistant starch. It adds that some types of resistant starch favor butyrate production.

At autopsy in people who died suddenly, the colon contents held 131 mmol/kg of SCFAs in the cecum, the first part of the colon. That fell to 80 in the descending colon, while the end of the small intestine (terminal ileum) held only 13.

A tracer study in 21 young and 40 older adults estimated butyrate production in a pool that may represent the gut absorbing bacterial fatty acids. In young adults, production was 28 µmol a minute on placebo and 44 on inulin (30 g a day for a week). In older adults it was 14 and 20, so they made less. On placebo that is about 3.6 g of butyric acid a day in young adults and 1.8 g in older ones (our arithmetic).

Colon cells take up most of it, so little reaches the blood

In the autopsy study, acetate was the main SCFA in every sample. But the mix changed from the colon contents to portal blood (from gut to liver) to the hepatic vein (leaving the liver). The authors read this as greater uptake of butyrate by the colon lining and of propionate by the liver. Total SCFAs in blood were 375 µmol/L in the portal vein, 148 in the hepatic vein and 79 in peripheral blood.

In 20 healthy adults, plasma butyrate was a median of 2.02 µmol/L after a low-SCFA diet and 2.85 µmol/L after a high-SCFA diet. This helps explain a pilot in which 4 g a day of oral sodium butyrate did not raise plasma or fecal butyrate.

It is the main fuel of colon cells

In Roediger’s experiments on cells from 14 human colon specimens, butyrate supplied 73% to 75% of oxygen use when it was the only fuel. With glucose present it supplied 59% to 72%. In the ascending colon, glucose’s share of oxygen use fell from 85% to 41% when butyrate was added.

In germ-free mice, colon cells were short of energy, with less oxidative phosphorylation and ATP (the cell’s energy molecule) and more autophagy (self-digestion). Adding butyrate rescued their mitochondrial respiration. The authors conclude that butyrate worked here as an energy source, not as an enzyme inhibitor.

In a second paper in 1980, Roediger found that descending colon cells from patients with ulcerative colitis oxidized less butyrate than cells from controls. That held for active and quiet disease (4 acute, 6 quiet and 7 control subjects). He suggested that colitis is an energy-deficiency disease of the colon lining. That is a hypothesis from cell experiments, and the trials of butyrate in colitis (above) have not settled it.

It quiets inflammatory signals

A review lists two main mechanisms. Butyrate stops the inflammatory switch NF-kappaB from turning on, and it blocks histone deacetylation, a process that helps control which genes are active. The review also warns that the effects depend on the concentration and the model and that human data are limited.

In 11 people with distal ulcerative colitis, 6 had butyrate enemas and 5 placebo for up to 8 weeks. Butyrate cut the number of macrophages (immune cells) with active NF-kappaB, and disease activity fell with them. In mice, butyrate made by gut bacteria raised the number of colon regulatory T cells, which damp inflammation.

In 16 healthy volunteers and 35 patients with ulcerative colitis in remission, enemas did not change the mucus layer genes MUC2 and TFF3. The fold changes were near 1, meaning no change.

Cancer cells treat it differently

In colon cell experiments, normal cells burn butyrate for energy, so it fuels their growth. Cancerous cells rely on glucose instead (the Warburg effect), so butyrate builds up in them. There it acts as a histone deacetylase inhibitor, which slowed their growth. This is a cell result about how one molecule is handled, and none of the trials above tested cancer prevention.

Dairy fat carries a little, bound in fat

In milk fat, butyric acid is part of triglycerides. FAO and WHO note that in cow milk all of it sits at the sn-3 position of the glycerol backbone. PubChem puts butter at 4 to 5% butyric acid as an ester. A review says the free acid is absorbed rapidly in the upper gut, which limits its use as a supplement.

We found no study that measured how much butyrate from butter or milk reaches the colon.

What has been seen in people

The doses in the trials covered a range of about 27-fold, from 0.12 to 3.2 g of butyric acid a day (our arithmetic). Compare that with 0.19 g in a cup of milk. Gut bacteria make about 2 to 4 g a day in a tracer model. The chart puts them on one scale.

The trial results do not follow the dose. The 150 mg a day trial in children found a large remission gap, while the 300 mg a day trial found none. The 4 g a day pilots in ulcerative colitis and metabolic syndrome were small and mixed. In adults with ulcerative colitis, a lower dose of 600 mg a day did better than placebo on the measures it reported.

The best evidence is that butyrate enemas do not clearly work in ulcerative colitis. Oral products have helped in some trials of bowel disease, irritable bowel syndrome and obesity. And the results do not line up with the dose.

How much butyric acid (butyrate) do you need?

No official body sets a daily amount of butyric acid. The FDA has set no Daily Value for it, and the EU no Reference Intake. We found no intake value in the 2010 FAO and WHO report on fats, which lists dairy fat as its typical source.

Your body makes it from fiber, so the practical target is fiber. The FDA Daily Value for dietary fiber is 28 g a day. A review of national surveys says only about 5% of the US population meets fiber recommendations.

How much the gut makes is hard to measure. In a tracer study, older adults made less butyrate in the model pool than young adults: 14 against 28 µmol a minute on placebo. A week of inulin raised both. Dairy adds little by comparison: 0.19 g in a cup of semi-skimmed milk and 0.002 g in a large egg in our USDA ranking.

We found no disease named for a lack of butyric acid. In ulcerative colitis, butyrate-making bacteria are less common (127 patients against 87 controls) and colon cells oxidize less butyrate. Whether that causes the disease or follows it is not known.

Forms of butyric acid (butyrate): absorption and effects

Butyrate reaches people in several forms. There is the butyrate bacteria make in the colon, and butyric acid bound in the fat of butter and milk. Supplements come as plain sodium butyrate, coated or microencapsulated sodium butyrate, calcium butyrate and the ester tributyrin, and there are enemas. The pure acid is not used because of its smell and taste.

The honest bottom line is that most trials used coated or microencapsulated sodium butyrate. The only head-to-head comparison we found, sodium against calcium butyrate in fatty liver disease, saw no change in liver fat with either.

Forms matter because uncoated butyrate is absorbed quickly in the upper gut, says a review whose authors also run butyrate trials. So trial products are coated to open in the colon. We found no study that compared coated with plain butyrate.

One pilot that measured blood and stool butyrate found no rise; it used 4 g a day of sodium butyrate capsules, coating not stated. A later trial of 1,875 mg a day found serum butyrate rose.

The key trials above used sodium butyrate, mostly coated or microencapsulated (wrapped in tiny capsules), for ulcerative colitis, Crohn’s disease, IBS and obesity. Calcium butyrate was used for IBS in children, enemas for ulcerative colitis, and fiber diets for fecal butyrate.

Form	What it is	What studies show	Source
Made by gut bacteria	Butyrate produced in the colon when bacteria ferment fiber and resistant starch	The main source. At autopsy colon contents held 131 mmol/kg of short-chain fatty acids in the cecum, and the colon lining takes up most of the butyrate. Potato starch raised fecal butyrate in 174 adults, but maize starch, inulin and one potato side dish did not.	1, 2, 3, 4
Butter and dairy fat	Butyric acid bound in milk fat triglycerides	PubChem puts butter at 4 to 5% as an ester, and about a third of milk triglycerides hold one molecule. In cow milk fat it sits at the sn-3 position. Butter raised LDL cholesterol in a trial, and we found no trial that measured gut butyrate after butter.	25, 6, 26, 7
Free butyric acid	The liquid acid, a corrosive liquid with a rancid odor	Not used as a supplement: the authors of one trial call direct supplementation not feasible because of its unpleasant taste and odor, and a review says its rancid smell and rapid upper-gut absorption limited its use. PubChem lists it as a food flavoring with a butter, cheese and sour profile.	25, 8
Sodium butyrate, coated or microencapsulated	The sodium salt, coated to release in the colon	The form in most oral trials: 4 g a day (ulcerative colitis, in pH-coated tablets), 1.5 g and 1.875 g a day (adults with diabetes or obesity), 600 mg a day (ulcerative colitis) and 300 mg and 150 mg a day (children). Results ranged from none to large. A pilot at 4 g a day found no rise in blood or fecal butyrate, and a later trial at 1.875 g a day did find serum butyrate rise.	10, 11, 12, 13, 14, 15, 9
Calcium butyrate	The calcium salt	500 mg a day helped children with irritable bowel syndrome in one trial, and a 500 mg tablet with zinc and vitamin D3 improved a fatty liver index. In the one head-to-head trial, 1,000 mg a day of the calcium and the sodium salt both left liver fat unchanged, and each moved different markers.	16, 17, 18
Tributyrin	A triglyceride with three butyrate molecules, a prodrug the body splits; also found in butter	150 to 200 mg/kg three times a day gave a median blood butyrate of 52 µM in cancer patients, and 500 mg three times a day changed butyrate uptake in Parkinson disease. It has a cheesy, fecal aroma and a bitter taste, which has limited its use in food.	19, 20, 22
Butyrate-enriched triglycerides	Butyrate and hexanoate esterified to long-chain fatty acids (a branded product)	Released its butyrate mostly in the small intestine in a lab gut model, and the medium dose raised blood butyrate after a meal in 12 men without changing any metabolic marker. Two authors work for the fat company AAK.	21
Butyrate enemas	A sodium butyrate solution given into the rectum	A nightly 80 mM enema did no better than saline in 38 people. A review of 8 trials says the evidence does not support enemas in ulcerative colitis.	23, 24

Here are the form-specific and head-to-head studies, strongest evidence first, 4 in all.

Is butyric acid (butyrate) safe? Supplements, dose and interactions

Butyrate that your gut makes and the butyric acid in dairy fat are not described as a safety concern in any source we found. We found no upper limit and no recommended intake for butyric acid from any authority. Supplements are another matter.

The trials tested specific products at specific doses, for up to 6 months in the cards above. Several reported no side effects. There were none in the two children’s bowel disease trials (150 mg and 300 mg a day). There were also none with 4 g a day alongside mesalazine, or with the calcium butyrate tablet.

The obesity trial in children reported brief mild nausea and headache in 2 of 54. The trials ran 6 months at most, so long-term safety is untested.

• No limit and short trials. We found no upper limit from any authority, no trial in pregnancy or breastfeeding and no study of drug interactions. In cancer patients, 150 to 200 mg/kg of tributyrin three times a day caused no dose-limiting toxicity; only the pill count stopped higher doses. Ask a doctor first if you are pregnant, breastfeeding or taking medicines.
• Smell, taste and the pure acid. Butyric acid has a penetrating, rancid odor, with published odor thresholds from 0.001 to 9 mg per cubic meter (PubChem). PubChem lists the pure acid as corrosive to metals and tissue, so it is not a product to swallow. Supplements use salts such as sodium butyrate or calcium butyrate, or the ester tributyrin, which has its own cheesy, fecal aroma and bitter taste.
• Sodium and calcium. By our arithmetic from the formula, sodium butyrate is about 21% sodium by weight. So a 4 g dose carries about 0.8 g of sodium, which matters on a low-sodium diet. Calcium butyrate is about 19% calcium, so 500 mg carries about 94 mg.
• Bowel disease and other treatments. The oral trials gave butyrate as an add-on to standard treatment, and one pediatric trial found no gain from it. Butyrate should not replace prescribed treatment for ulcerative colitis, Crohn’s disease or irritable bowel syndrome. If you have bowel symptoms, ask a doctor before trying a supplement.

How to get more butyric acid (butyrate)

• Feed the bacteria that make it. Fiber and resistant starch are their fuel. Resistant starch from potatoes raised fecal butyrate in 174 healthy adults, while maize starch and inulin did not, so the response depends on the person. Only about 5% of the US population meets fiber recommendations, and the Daily Value for dietary fiber is 28 g.
• Keep dairy in perspective. A cup of semi-skimmed milk holds 0.19 g of butyric acid, far less than the gut makes. In a 4-week trial, 50 g a day of butter raised LDL cholesterol by 0.42 mmol/L more than coconut oil. So butter is not a butyrate shortcut.
• Ask before starting a supplement. The trials of butyrate supplements are small and mixed, and the products differ in dose, coating and brand. If you have bowel symptoms, a doctor can rule out disease before you try one.

History of butyric acid

Butyric acid was first noticed in butter. The French chemist Michel Eugène Chevreul saw it in impure form in 1814, and had purified it enough to characterize it by 1818. He claimed as early as 1815 that he had found the substance behind the smell of butter. A rival chemist, Henri Braconnot, was also working on butter, which led to a dispute over who came first.

Chevreul’s detailed account came in 1823. By 1824, according to a history of nutrition science, he had shown that fats are esters of glycerol and fatty acids of different chain lengths. The name butyric acid comes from the Greek word for butter.

The gut story came much later. In 1980 Roediger showed that isolated human colon cells burn butyrate as their main fuel. Later that year he suggested that colitis might be a disease of colon cells that cannot use it.

In 1987 Cummings and colleagues measured short-chain fatty acids in the gut and blood of people who died suddenly. This showed that bacteria ferment carbohydrate in the human colon on a large scale.

Butyrate was soon tried as a treatment: SCFA enemas in 1995 and butyrate enemas in 1996, then oral tablets in 2000 and 2005. In 2025 came a multicenter trial of microencapsulated sodium butyrate in ulcerative colitis.

In 2013 a mouse study showed that butyrate from gut bacteria can raise regulatory T cells. That opened a new line of research on how fiber affects immunity.

Microencapsulated sodium butyrate then became available as a supplement in Poland. A 2013 review described how it solved two problems of the pure acid: its rancid smell, and its quick absorption in the upper gut. We found no trial that compared coated with plain butyrate.

Frequently asked questions about butyric acid

Is butyric acid bad for you?

Not at food amounts, as far as published sources show. It is made in your own gut, it is found in butter and milk fat, and the main drawback is its smell. Colon cells in a dish drew 73% to 75% of their oxygen use from it.

In dairy fat the amounts are small: 0.19 g in a cup of semi-skimmed milk in our USDA ranking. In one 4-week trial, 50 g a day of butter raised LDL cholesterol 0.42 mmol/L more than coconut oil. That comes from the whole fat and cannot be credited to butyric acid.

How much butyric acid do you need per day?

No daily amount is set. The FDA has set no Daily Value and the EU no Reference Intake, and your body makes it from fiber. A tracer-model study estimated about 1.8 g a day in older adults and 3.6 g in young adults before inulin. The practical step is fiber: the FDA Daily Value is 28 g, and only about 5% of the US population meets recommendations.

Do butyrate supplements work?

The evidence is limited and mixed. In 72 children with bowel disease, 150 mg of sodium butyrate twice a day did not raise remission. Another trial of 88 children found 81.82% remission against 47.73%.

In irritable bowel syndrome, 66 adults on microencapsulated sodium butyrate had less pain on passing stool but no clear drop in overall pain. A 2026 review calls for larger trials with standard formulations before routine use.

Can butyrate treat ulcerative colitis or Crohn’s disease?

Not on current evidence. A review of 8 trials of butyrate enemas in 227 people with ulcerative colitis found only 1 with a clear difference in disease activity. A nightly 80 mM enema did no better than placebo (37% against 47% improved).

Oral butyrate looked better as an add-on. In 98 adults with ulcerative colitis, 31.4% on microencapsulated sodium butyrate reached clinical remission. In an open-label pilot with no placebo group, 7 of 13 people with Crohn’s disease reached remission. Do not replace prescribed treatment.

How can I raise butyrate with food?

Eat more fiber and resistant starch, since gut bacteria make butyrate from them. In 174 healthy adults, resistant starch from potatoes raised fecal butyrate most, while maize starch and inulin did not.

A diet rich in arabinoxylan and resistant starch raised it in 19 adults with metabolic syndrome. One potato side dish a day did not change it in 50 adults. Responses differ from person to person.

Why does butyric acid smell so bad?

The pure acid has a penetrating, rancid odor, according to PubChem, and it is found in butter, milk fat and sweat. Its ester tributyrin has a cheesy, fecal aroma and a bitter taste in food tests. That is why supplements use salts such as sodium butyrate or coated and microencapsulated forms. At very low levels the same compound is used as a butter, cheese or sour flavoring.

Does butter give you butyrate in your gut?

We found no study that measured it. Butter carries butyric acid bound in fat, 4 to 5% as an ester according to PubChem. A review says the free acid is absorbed rapidly in the upper gut.

The gut makes about 2 to 4 g a day in a tracer model, against 0.19 g in a cup of milk. Fiber is the major lever.