Supplement analysis backed by scientific evidence · PT

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Moderate evidenceGut health

Lactobacillus Reuteri

L. reuteri DSM 17938 reduces crying in breastfed infants with colic — the effect is real but restricted to that population; in formula-fed infants it does nothing. Adult claims (H. pylori, cholesterol, oral health, testosterone) are far weaker than the marketing suggests.

What the science says

  • Reduces crying in breastfed infants with colic Moderate evidence

    An individual-participant-data meta-analysis of four RCTs (n=345) found infants given L. reuteri DSM 17938 were about twice as likely to halve their crying time at day 21 (NNT ≈ 2.6), with a mean reduction near 25 minutes/day. Crucially, the benefit was confined to breastfed infants — in formula-fed infants there was no effect. A Cochrane review of probiotics to prevent (rather than treat) colic found the evidence too uncertain to recommend.

  • Improves H. pylori eradication tolerance Limited evidence

    Small RCTs suggest adding L. reuteri to eradication regimens reduces nausea and diarrhoea and may marginally raise eradication rates, but trials are small, heterogeneous in strain and dose, and the pooled effect on eradication is not convincing. Treat this as adjunctive at best.

  • Lowers LDL cholesterol (L. reuteri NCIMB 30242) Limited evidence

    Two small industry-sponsored RCTs of a bile-salt-hydrolase-active strain reported LDL reductions of roughly 8-12% over 9 weeks. These have not been independently replicated, and the strain is different from the colic strain — the results do not transfer between products.

  • Raises testosterone or improves oral health Limited evidence

    Testosterone claims trace to a single mouse study and have no human RCT support. Oral strains (DSM 17938 with ATCC PTA 5289 lozenges) show modest reductions in gingival inflammation in small trials, but the evidence base is thin and short-term.

Dosage & safety

Studied doseInfant colic: 1×10^8 CFU (100 million) of L. reuteri DSM 17938 once daily as oil drops, for 21-28 days. Adult GI and oral uses in trials: 1×10^8 to 2×10^8 CFU twice daily. Strain identity matters more than dose — check the full strain designation on the label, not just the species.
SafetyWell tolerated; the colic trials reported no excess adverse events versus placebo. As with other Lactobacillus species, avoid in immunocompromised infants and adults, those with central venous catheters, prosthetic valves or short bowel syndrome, given rare reports of bacteraemia. Infant drops are oil-based and some formulations contain sunflower oil and vitamin D — check for duplicate vitamin D dosing. Persistent inconsolable crying in an infant needs medical assessment before being labelled colic; probiotics are not a substitute for ruling out cow's milk protein allergy, reflux disease or infection.

Scientific references

Where to buy

Nature's Way, Primadophilus® Reuteri Probiotic, 5 Billion CFU, 90 Capsules

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