my postbiotic butyrate

Most people asking about postbiotics have already tried a probiotic and want to know if this is a better version. These are the questions our naturopaths ask in store.

A good fit if

• Your IBS has been medically diagnosed and you'd like to try the option with the best early evidence
• You need something shelf-stable, for travel or because you'd forget to refrigerate it
• The product names its strain code, so you can match it to the research
• You're willing to give it at least four weeks, which is how long the shortest trials ran

Check with us first if

• You're pregnant or breastfeeding. There's no information on postbiotics in pregnancy or breastfeeding, and urolithin A must not be used at all.
• Your immune system is weakened. That's the group where live versus killed bacteria should matter most, and there's no data.
• You take any regular medicine. There's no interaction data for any postbiotic, which isn't the same as no interactions.
• You're buying for a baby or child. Research in infant formula found postbiotics safe but not effective, and infant feeding is a decision for a paediatrician or child health nurse.
• You have gut symptoms without a diagnosis. The only permitted IBS claim applies to medically diagnosed IBS, so see a doctor first.
• You take prescription medicine. Check with your doctor, pharmacist or our naturopaths before you start.

• Heat-killed whole bacteria (paraprobiotics, tyndallised). Best known for: The most common postbiotic on the market. No fridge needed, no live count to lose, and it can't settle in your gut. Absorption: This is where most of the human evidence sits: IBS symptom severity, immune markers in older adults, breath and mouth bacteria, and body composition. Every result belongs to a named strain. Typical use: Capsules, tablets and lozenges. Allowed under the species name, but the rules don't say whether a killed organism counts.
• Cell components (cell-free extracts, exopolysaccharides, surface layer proteins, extracellular vesicles). Best known for: Pieces of bacterial cells rather than whole cells. Absorption: Animal studies only. Typical use: We found no Schedule 1 item for any of them by name, so each product needs its own status check.
• Sodium butyrate. Best known for: A compound gut bacteria make, supplied ready-made. Absorption: Short-chain fatty acids were the stronger group in animal obesity studies. We found no human trial of sodium butyrate. Typical use: The only allowed butyrate active. By mouth only, adults only, and no more than 1,200 mg a day.
• Butyric acid. Best known for: The free acid form of butyrate. Absorption: Not assessed. Typical use: Allowed only as a flavour or fragrance, never as an active. A label listing it as an active has a problem.
• Propionate salts (sodium and calcium propionate). Best known for: The other major short-chain fatty acid. Absorption: Not assessed. Typical use: Allowed only as an inactive ingredient, so there's no Australian pathway as an active. Calcium propionate is capped at 1 mg a day.
• Urolithin A. Best known for: A compound gut microbes make from ellagitannins. Absorption: Covered on its own page. Typical use: Limited to one company until 19 September 2027. Adults only, not in pregnancy or breastfeeding, for four months or less.

Reference values. There isn't one. Postbiotics aren't a nutrient, and Australian rules don't list them under that name. Instead, they list each species and compound one by one.

Typical supplemental range. Trial doses are specific to each strain, so they don't carry over from one product to another. Heat-killed Lactobacillus gasseri TMC0356 was tested at 1.0 × 10⁹ cfu a day for 4 weeks. Heat-killed ET-22 lozenges were taken three times a day for 4 weeks, with the count not stated in the study summary. The IBS review didn't state doses at all, so its result can't yet be matched to a product.

Upper level. The NHMRC hasn't set an upper limit. The legal daily limits in a listed medicine are 1,200 mg of sodium butyrate (taken by mouth, adults only) and 1,000 mg of urolithin A (for four months or less). The probiotic species have no limit.

Worth knowing. Give it time. The trials ran from 4 weeks to six menstrual cycles, and none was a short course. What you need depends on your age, diet and health, so talk to one of our naturopaths.

Food first, where the diet allows it.

• Fermented foods: a plausible source, but no study has measured the postbiotic content of any food
• Infant and follow-on formula with added postbiotics: the only food with postbiotic trial data; safe but not effective in the infant trials
• Dietary fibre: not a postbiotic itself, but what gut bacteria ferment into butyrate

If any of these sound like you, talk to one of our naturopaths or your doctor before you start.

• You're looking at sodium butyrate. Its label must say 'Adults only', it's by mouth only, and the maximum is 1,200 mg a day.
• You're looking at urolithin A. It's adults only, not for pregnant or breastfeeding women, for four months or less, and the maximum is 1,000 mg a day.
• You're pregnant or breastfeeding. We found no safety data on postbiotics.
• Your immune system is weakened. We found no data.
• You take regular medicines. We found no interaction data.
• Babies and children. Infant formula trials found postbiotics safe but not effective, and data on follow-on formula couldn't be combined.
• Your gut symptoms haven't been diagnosed. The only allowed IBS indication is for medically diagnosed IBS.
• If you take prescription medicines, check with your doctor, pharmacist or our naturopaths before you start.