Prebiotics

Is a synbiotic better than a prebiotic alone?

Updated 4 Nov 2026

Short answer

Not clearly. A synbiotic combines a prebiotic with a probiotic.[1] Results depend on the outcome, and few studies compare the two directly:[2][3][4][5]

  • Inflammation: of 8 studies that compared them, 2 found a drop in markers only with synbiotics and 1 found a greater effect with synbiotics.[2] The title of a 2025 review of 90 trials says that synbiotics surpass prebiotics. In adults, both lowered markers. The effect was larger with synbiotics for interleukin 6 (IL-6; standardized mean difference -2.02 against -0.41) and larger with prebiotics for C-reactive protein (CRP; -0.81 against -0.51). Synbiotics did not help in children.[3]
  • Respiratory infections: the odds ratios against placebo were similar, 0.73 with prebiotics and 0.75 with synbiotics.[4]
  • Irritable bowel syndrome: neither showed a significant benefit in a 2024 review.[5]
  • Constipation: a 2024 review of 37 trials found that lactulose and synbiotics raised stool frequency, with moderate to very low certainty, and its authors highlighted the effect of synbiotics.[6]

Sources (6)

  1. Probiotics: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements, 2025. ods.od.nih.gov
  2. Short-chain fatty acids, prebiotics, synbiotics, and systemic inflammation: a systematic review and meta-analysis. McLoughlin RF, Berthon BS, Jensen ME, Baines KJ, Wood LG Am J Clin Nutr, 2017. PMID 28793992
  3. The effects of synbiotics surpass prebiotics in improving inflammatory biomarkers in children and adults: A systematic review, meta-analysis, and meta-evidence of data from 5207 participants in 90 randomized controlled trials. Zhang Y, Hong J, Zhang Y, Gao Y, Liang L Pharmacol Res, 2025. PMID 40581234
  4. The Effects of Prebiotics, Synbiotics, and Short-Chain Fatty Acids on Respiratory Tract Infections and Immune Function: A Systematic Review and Meta-Analysis. Williams LM, Stoodley IL, Berthon BS, Wood LG Adv Nutr, 2022. PMID 34543378
  5. The Efficacy of Probiotics, Prebiotics, Synbiotics, and Fecal Microbiota Transplantation in Irritable Bowel Syndrome: A Systematic Review and Network Meta-Analysis. Wu Y, Li Y, Zheng Q, Li L Nutrients, 2024. PMID 38999862
  6. Network meta-analysis of probiotics, prebiotics, and synbiotics for the treatment of chronic constipation in adults. Deng X, Liang C, Zhou L, Shang X, Hui X, Hou L, et al. Eur J Nutr, 2024. PMID 38693449

More about prebiotics

What are prebiotics?Do prebiotics change your gut bacteria?How long do prebiotics take to work?Which foods contain prebiotics?What are prebiotics used for?Are prebiotics the same as fiber?

For education; not medical advice. Talk to a doctor before you start, stop or change a supplement.