Supplement analysis backed by scientific evidence · PT

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Moderate evidenceGut health

Synbiotics

Products combining a probiotic with a prebiotic. Meta-analyses show benefits similar to probiotics alone for constipation and IBS; convincing evidence that the combination beats its parts is still missing.

Evidence last reviewed: August 2026

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What the science says

  • Chronic constipation Moderate evidence

    A systematic review and meta-analysis of randomized controlled trials found that probiotics and synbiotics increased stool frequency and improved stool consistency in adults with chronic constipation, with modest effect sizes and considerable heterogeneity.

  • IBS symptoms Moderate evidence

    A systematic review and network meta-analysis of probiotics, prebiotics, synbiotics and fecal transplantation in IBS ranked several interventions above placebo for symptom relief, but confidence in the ranking is limited by small, varied trials.

  • Overall efficacy and safety Moderate evidence

    An umbrella review of systematic reviews and meta-analyses concluded that probiotics, prebiotics and synbiotics have generally favorable but modest effects across a range of outcomes, with quality of evidence commonly rated low.

Dosage & safety

Studied doseNo standard formula. Products typically supply 1–10 billion CFU alongside 1–5 g of prebiotic; the studied doses belong to specific products, not to synbiotics as a class.
SafetyWell tolerated by healthy adults; early gas and bloating are common, driven mostly by the prebiotic. Caution with live organisms in severely immunocompromised or critically ill patients, where trials of synbiotics have reported harm.

Scientific references

Where to buy

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