Streptococcus Thermophilus

probioticlactic acid bacterium

What is it

Streptococcus thermophilus is a Gram-positive, facultatively anaerobic, homofermentative lactic acid bacterium and one of the two starter cultures (alongside Lactobacillus delbrueckii subsp. bulgaricus ) traditionally required by international standards to be present in yoghurt. It is one of the most economically important industrial dairy microorganisms and, although taxonomically grouped with the streptococci, is non-pathogenic and bears the Generally Recognised As Safe (GRAS) and EFSA Qualified Presumption of Safety (QPS) status. The species ferments lactose to lactic acid via the EMP pathway, expresses a beta-galactosidase that contributes to lactose digestion in the small intestine, and produces extracellular polysaccharides that contribute to yoghurt texture. It is widely used as a probiotic species in fermented dairy products, infant formulas, and capsule supplements, often in combination with bifidobacteria and other lactobacilli.

Evidence for 5 uses

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Lactose maldigestion

Strong Evidence

Live S. thermophilus and L. bulgaricus in yoghurt deliver bacterial beta-galactosidase to the small intestine, improving lactose digestion and reducing symptoms in lactose-intolerant individuals. This is one of the best-established probiotic health claims, recognised by EFSA for live yoghurt cultures.

Antibiotic-associated diarrhoea (in multi-strain blends)

Good Evidence

Multi-strain probiotics often containing S. thermophilus reduce the incidence of antibiotic-associated diarrhoea in children and adults in meta-analyses. The specific contribution of S. thermophilus within these blends is difficult to isolate.

Infectious diarrhoea (acute, especially paediatric)

Good Evidence

Probiotic blends containing S. thermophilus alongside L. rhamnosus , Bifidobacterium species, or Saccharomyces boulardii reduce duration of acute infectious diarrhoea in children in meta-analyses, by roughly 1 day on average.

Necrotising enterocolitis prevention in preterm infants

Good Evidence

Multi-strain probiotic combinations including S. thermophilus reduce necrotising enterocolitis and all-cause mortality in preterm infants in meta-analyses of multiple RCTs. Specific strain and dose recommendations vary by neonatology guideline.

Inflammatory bowel disease (pouchitis maintenance)

Good Evidence

The VSL#3 / Visbiome combination containing S. thermophilus together with several lactobacilli and bifidobacteria reduces pouchitis recurrence in chronic relapsing pouchitis after ileal pouch anal anastomosis, supported by RCT evidence.

Dosage

Probiotic doses of S. thermophilus are commonly 1-10 billion colony forming units (CFU) per day as part of multi-strain formulations; clinical trials investigating digestive, immune, or antibiotic-associated indications typically use 1-25 billion CFU/day for 1-12 weeks. As a yoghurt starter, typical yoghurt contains approximately 10^7-10^8 CFU/g of S. thermophilus at consumption. Single-strain S. thermophilus supplements are less common than multi-strain blends.

Safety

S. thermophilus has a strong safety record with QPS status in the EU and GRAS designation in the US; it is non-pathogenic, non-toxigenic, and does not carry transmissible antibiotic resistance. Adverse effects at typical doses are limited to mild bloating, gas, and changes in stool pattern in the first days of use. Theoretical risk of bacteraemia in severely immunocompromised patients (including those with central venous catheters or short bowel syndrome) applies to all live probiotic species and warrants caution in these populations. No clinically significant drug interactions are established. Safety in pregnancy and lactation at normal intakes is uncontested.

References

Wikidata: Streptococcus thermophilus (Q1041276) — Wikidata link
NIH Dietary Supplement Label Database: Streptococcus Thermophilus — DSLD link
EFSA Qualified Presumption of Safety (QPS) list — EFSA link

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Evidence-based·How we grade evidence

Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.