Supplements
Sodium Butyrate Side Effects: What the Trials Actually Found
Four randomized trials, two of which found gut symptoms improved. The genuine downsides are the sodium you swallow with it, a small blood pressure trial that went the wrong way, and a smell that ends more supplement habits than any side effect.
If you went looking for sodium butyrate side effects, here is the short version. In the randomized human trials that exist, sodium butyrate is well tolerated. The gut complaints people worry about mostly did not show up, and in two trials the gut symptoms actually got better. The two things worth knowing before you buy it are the sodium you swallow along with it, and one small blood pressure trial that came out the wrong way.
This is education, not medical advice. If you take blood pressure medication or have kidney problems, the sodium part below is a conversation with your prescriber.
What the human trials actually report
Three randomized trials give the clearest picture, and none of them read like a warning label.
In the largest recent one, 52 people with type 2 diabetes who also met the criteria for irritable bowel syndrome took either 1.5 g a day of microencapsulated sodium butyrate or a placebo for 12 weeks. The butyrate group reported significantly less abdominal pain, less diarrhea, and less bloating. Body weight, HbA1c, and HOMA-IR, the standard insulin resistance index, all came down as well, and nothing moved in the placebo group (Panufnik, 2026). Those metabolic markers are worth a look if you are watching the markers that shift before a diabetes diagnosis.
An earlier trial gave 66 people with IBS microencapsulated sodium butyrate on top of their existing treatment. Pain during bowel movements dropped significantly by week 4, with urgency and bowel habit improving by week 12. Abdominal pain, flatulence, and disordered defecation improved too, but not by enough to be statistically significant (Banasiewicz, 2013).
The third trial is the useful one for dose. Fifty-three people with type 1 diabetes took 3.6 g of sodium butyrate a day for 12 weeks, which is more than double what most labels suggest. It did not reduce intestinal inflammation and did not move kidney markers or HbA1c. It also did not make gastrointestinal symptoms worse (Tougaard, 2022). That is a null result on the benefit side and a reassuring one on the tolerability side.
Does sodium butyrate cause diarrhea?
Not in the trials, at either 1.5 g or 3.6 g a day. The reports of loose stools you find in forums and product reviews are real experiences, but they are anecdotal, they usually come from the first week, and they usually come from people who started high.
There is a sensible mechanism behind it. Butyrate is osmotically active, and swallowing a gram and a half of anything fermentable can loosen things up while your gut adjusts. If it happens to you, cut the dose in half and build back up. Nothing in the published record suggests it becomes a lasting problem, and the two IBS trials point the other way entirely.
How much sodium is in a sodium butyrate supplement?
This is the side effect nobody puts on the front of the bottle, and it is pure chemistry. Sodium butyrate is roughly 21 percent sodium by weight. So:
- 1.5 g a day, the dose in the diabetes trial, carries about 310 mg of sodium.
- 3.6 g a day, the dose in the type 1 trial, carries about 750 mg.
The general daily ceiling most guidelines use is 2,300 mg. A few hundred milligrams is not a crisis on its own. It matters if you are already running high, if you are on a sodium-restricted diet, or if you are one of the many men who has never actually measured his blood pressure properly at home. It also matters more at the high end, where the sodium from a single supplement starts to look like a third of your budget.
Sodium butyrate and blood pressure: the result that should give you pause
This is the one finding in the whole literature that deserves your attention, and most articles on this topic leave it out.
Researchers took 23 people with hypertension, stopped their blood pressure medication with a four week washout, then gave them either daily oral sodium butyrate capsules or a placebo containing an equivalent dose of sodium chloride, for four weeks. Daytime 24 hour systolic blood pressure went up by 9.63 mm Hg in the butyrate group compared with placebo, and diastolic went up by 5.08 mm Hg. Plasma butyrate rose while fecal butyrate did not, which confirms it was being absorbed. The authors concluded that butyrate does not have beneficial effects on human hypertension and called for caution in future trials (Verhaar, 2024).
Three things keep this honest. First, the placebo was sodium matched, so this is not simply the salt. Second, it is 23 people whose blood pressure medication had been deliberately withdrawn, which is an unusual setup and not the situation you are in. Third, it points the opposite way from the rodent work and from another small human trial: 60 people with type 2 diabetes taking sodium butyrate, inulin, or both for 45 days all had lower diastolic blood pressure than placebo (Roshanravan, 2017).
Two small trials pointing in opposite directions is not a settled answer. It is a reason to measure your own numbers if you start taking it, and a reason to raise it with your prescriber if you already treat hypertension.
Is sodium butyrate safe long term?
Honestly, nobody knows past three months, because nobody has run it longer.
The longest randomized human exposures on record are the two 12 week trials above, and neither reported serious adverse events. A separate three month trial of a butyrate based formula in 50 people with liver steatosis and metabolic syndrome states plainly that no subject experienced any adverse events during the trial (Fogacci, 2024). The head to head absorption study of three butyrate forms also reported that all treatments were well tolerated with zero adverse events (La Monica, 2025).
So the short term safety record is clean. Beyond 12 weeks is an empty space rather than a red flag. That is a real distinction, and it is the same one that applies to most of the supplement shelf.
The side effect nobody warns you about: the smell
Butyric acid is the compound behind the smell of rancid butter. That is not a metaphor, it is the same molecule. The reason products use sodium butyrate at all is that direct supplementation with butyric acid is not feasible because of the taste and odor, which the trial authors state outright (Panufnik, 2026).
The salt form tones it down. It does not eliminate it. Capsules handle it if you swallow them quickly with water, but a burp an hour later will remind you what you took. For a lot of men this is the thing that ends the habit, not any medical issue.
What this means if you are picking a butyrate supplement
The side effect profile is one input. The bigger question is whether the form you buy puts any butyrate in your blood at all, which we covered in detail in our breakdown of which butyrate form actually reaches your bloodstream.
The one head to head human comparison dose matched three forms at 786 mg of butyric acid in 10 healthy men. Lysine butyrate and sodium butyrate both put more butyrate in the blood, and got it there faster, than tributyrin. Between lysine butyrate and sodium butyrate there was no significant difference in total exposure (p=0.660).
That matters here because the two genuine downsides of sodium butyrate, the sodium load and the smell, are both solved by lysine butyrate without giving up absorption. Lysine butyrate carries no sodium at all, and it is tasteless and water soluble, which is why it works in a drink. Ozzi uses 500 mg of L-lysine butyrate for exactly that reason, and Ozzi is operated by the same people who publish The Fitness Verdict, so take that as disclosure rather than a recommendation. To be clear about what the evidence supports: lysine butyrate did not beat sodium butyrate on blood levels in the only trial that compared them. It tied, and won on the practical stuff.
A note on butyrate and GLP-1
You will see butyrate sold on a GLP-1 angle, so here is where that sits. Butyrate stimulates the L-cells that release GLP-1 in mouse and cell studies, and human confirmation is still thin. The trial above found a significant increase in GLP-1 in the sodium butyrate arms compared with placebo, but that was a post hoc comparison across four groups of 15 people over 45 days (Roshanravan, 2017). Circulating GLP-1 is also cleared from the blood within minutes and commercial assays disagree with each other, which is part of why this question stays open.
The fair statement is that butyrate supports natural GLP-1 production in preclinical models. It is not a substitute for anything a doctor prescribes. Our wider look at what actually supports GLP-1 naturally puts it in context.
Who should hold off or ask first
- Anyone treating high blood pressure. The Verhaar result is small but it went the wrong way, and it is worth raising with your prescriber before you start.
- Anyone with kidney disease or on a sodium restricted diet. The sodium is not huge, but it is not nothing, and lysine butyrate exists.
- Anyone who reacts badly in week one. Halve the dose before you write the whole thing off.
The free version, first
Before you buy anything, remember that you manufacture butyrate yourself. Your gut bacteria make it by fermenting dietary fiber, and most men are nowhere near the intake that supports it. Our guide to how much fiber men actually need has the targets, and it costs nothing.
The bottom line
Sodium butyrate side effects are milder than the internet suggests. Across four randomized trials the gut complaints were largely absent, and in two of them gut symptoms improved. The real considerations are the sodium load at higher doses, one small blood pressure trial that argues for caution if you are hypertensive, an empty evidence space past 12 weeks, and a smell that ends more supplement habits than any side effect does. If the sodium or the smell is your sticking point, a different butyrate salt solves both. More on the rest of the shelf in our supplements coverage.
References
- Verhaar BJH, Wijdeveld M, Wortelboer K, et al. Effects of Oral Butyrate on Blood Pressure in Patients With Hypertension: A Randomized, Placebo-Controlled Trial. Hypertension. 2024. https://pubmed.ncbi.nlm.nih.gov/39034917/
- Panufnik P, Wiecek M, Szwarc P, et al. Effect of microencapsulated sodium butyrate on abdominal symptoms and carbohydrate metabolism in patients with type 2 diabetes: a randomized placebo-controlled trial. Sci Rep. 2026. https://pubmed.ncbi.nlm.nih.gov/41974937/
- Banasiewicz T, Krokowicz L, Stojcev Z, et al. Microencapsulated sodium butyrate reduces the frequency of abdominal pain in patients with irritable bowel syndrome. Colorectal Dis. 2013. https://pubmed.ncbi.nlm.nih.gov/22738315/
- Tougaard NH, Frimodt-Moller M, Salmenkari H, et al. Effects of Butyrate Supplementation on Inflammation and Kidney Parameters in Type 1 Diabetes: A Randomized, Double-Blind, Placebo-Controlled Trial. J Clin Med. 2022. https://pubmed.ncbi.nlm.nih.gov/35806857/
- Roshanravan N, Mahdavi R, Alizadeh E, et al. Effect of Butyrate and Inulin Supplementation on Glycemic Status, Lipid Profile and Glucagon-Like Peptide 1 Level in Patients with Type 2 Diabetes: A Randomized Double-Blind, Placebo-Controlled Trial. Horm Metab Res. 2017. https://pubmed.ncbi.nlm.nih.gov/28962046/
- Fogacci F, Giovannini M, Di Micoli V, et al. Effect of Supplementation of a Butyrate-Based Formula in Individuals with Liver Steatosis and Metabolic Syndrome: A Randomized Double-Blind Placebo-Controlled Clinical Trial. Nutrients. 2024. https://pubmed.ncbi.nlm.nih.gov/39125336/
- van Deuren T, Blaak EE, Canfora EE. Butyrate to combat obesity and obesity-associated metabolic disorders: Current status and future implications for therapeutic use. Obes Rev. 2022. https://pubmed.ncbi.nlm.nih.gov/35856338/
- La Monica MB, et al. Comparative pharmacokinetics of three oral butyrate forms in healthy men. J Exerc Nutr. 2025;8(1):4. Registered as NCT06700785
Common questions
Does sodium butyrate cause diarrhea?
Sodium butyrate did not cause diarrhea in the randomized trials. At 1.5 g a day in people with type 2 diabetes and IBS, diarrhea significantly decreased compared with placebo (Panufnik, 2026). At 3.6 g a day for 12 weeks in people with type 1 diabetes, gastrointestinal symptoms did not change in either direction (Tougaard, 2022). Loose stools reported in product reviews are usually first-week adjustment at a high starting dose. Halve the dose and build back up if it happens to you.
How much sodium is in a sodium butyrate supplement?
Sodium butyrate is about 21 percent sodium by weight. A 1.5 g daily dose carries roughly 310 mg of sodium, and a 3.6 g dose carries roughly 750 mg, against a general daily ceiling of 2,300 mg. That is manageable for most men and worth thinking about if you already run high, follow a sodium-restricted diet, or have kidney problems.
Does sodium butyrate raise blood pressure?
One small trial says it might. Twenty-three people with hypertension had their medication withdrawn, then took sodium butyrate or a sodium-matched placebo for four weeks. Daytime systolic blood pressure rose 9.63 mm Hg and diastolic rose 5.08 mm Hg versus placebo, and the authors urged caution (Verhaar, 2024). A different trial in 60 people with type 2 diabetes found lower diastolic pressure with sodium butyrate (Roshanravan, 2017). Two small trials disagreeing is not a settled answer, so raise it with your prescriber if you treat hypertension.
Is sodium butyrate safe to take every day long term?
The short-term safety record for sodium butyrate is clean. The longest randomized human exposures are 12 weeks, and none reported serious adverse events. A separate three-month trial of a butyrate-based formula in 50 people stated that no subject experienced any adverse events (Fogacci, 2024). Past 12 weeks, nobody has studied it, which is an absence of data rather than evidence of harm.
Why does sodium butyrate smell so bad?
Butyric acid is the same molecule responsible for the smell of rancid butter. Supplements use the sodium salt precisely because direct supplementation with butyric acid is not feasible on taste and odor grounds. The salt form reduces the smell but does not remove it, and burping after a capsule is a common complaint. Lysine butyrate is the form usually described as tasteless and water soluble.
Is lysine butyrate better than sodium butyrate?
On blood levels, lysine butyrate is not better than sodium butyrate. In the only head-to-head human comparison, lysine butyrate and sodium butyrate did not differ significantly on total butyrate exposure (p=0.660), though both beat tributyrin (La Monica, 2025). Lysine butyrate wins on the practical points instead: it carries no sodium and it dissolves in water, which is why it works in drinks rather than capsules.
