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Evidence first · Single-ingredient guide

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Probiotic Guide

Start with what qualifies as a probiotic, then evaluate products by strain transparency, CFU context, use case, and whether the evidence matches the intended outcome.

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Foundational guide

What are probiotics?

Learn what probiotics are, why evidence is strain-specific, how products differ, and how Probiotic Science reviews published studies, findings, and limitations.

Fast path

A strain-aware path through probiotic basics, CFU counts, IBS, antibiotic-associated diarrhea, women’s health, and product selection.

Probiotics are live microorganisms — most commonly particular strains of bacteria or yeasts — that are studied for their interactions with the human digestive system. Different products contain different strains and amounts, and research findings are typically specific to the exact strain studied rather than to probiotics in general. Probiotic Science is an independent project that organizes the scientific literature by strain and study, summarizing what researchers measured and reported and linking to the source papers. This material is for general information only and is not medical advice.

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Explore the evidence

Find the level of detail you need

Start with a focused question, open a research summary when you want more context, and compare products after you understand the evidence and tradeoffs.

Start with a question

Get a concise answer with evidence context and important limitations.

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Read the research

Open plain-language summaries when you want the study context, findings, and limitations.

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Compare products

Use the comparison after you know which product features and evidence considerations matter.

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Frequently asked questions

Common questions about probiotic

Choose a question for a concise answer, the supporting evidence, and the important limitations to keep in mind.

Product-selection path

Best Probiotic Supplements

An evidence-informed comparison of leading probiotic supplements, evaluated on strain characterization, labeled CFU, transparency, and testing.

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Research library

Featured probiotic research

Read plain-language summaries for a closer look at individual research questions, findings, and limitations.