Fermented Foods vs Probiotic Supplements: What Differs and What Studies Compared

How fermented foods differ from probiotic supplements in definition, live microbes, evidence and labeling, and what the few studies that compared a food with a capsule found.

Content last updated October 22, 2026. This page has not been medically reviewed.

Quick answer

A fermented food and a probiotic are not the same thing. A panel of the International Scientific Association for Probiotics and Prebiotics (ISAPP) said the terms "fermented food" and "probiotics" cannot be used interchangeably. [1] A fermented food can be healthy, and a probiotic can be useful, but neither result transfers to the other. This page is information only, not medical advice.

How the sources define the terms

Fermented food: the ISAPP panel defined these as foods and beverages made through desired microbial growth and enzymatic conversions of food components. [2]
Probiotic: live microorganisms which, when given in adequate amounts, confer a health benefit on the host. [3]
Where they overlap: the panel said fermented foods are not equivalent to probiotic foods. [1] It also said many fermented foods have no evidence that their live microbes provide health benefits. [1]

Probiotic products may be a yogurt or other fermented food, a dietary supplement, or a beauty product. [4] For the full definition page, see what probiotics are.

Documented differences

Question	What the sources say	Source
Must it contain live microbes?	No expectation that fermented foods must contain live microorganisms. [1]	ISAPP panel, 2021
Is the strain named and tested?	A food may be labelled "contains probiotics" only when strains are defined to the strain level and present in adequate numbers. [1]	ISAPP panel, 2021
How much research exists?	Except for yogurt and cultured dairy, few human clinical studies have verified benefits of fermented foods. [1]	ISAPP panel, 2021
How are products regulated?	The NHS says probiotics are generally classed as food rather than medicine in the UK. [5] NCCIH says many US probiotics are sold as dietary supplements that do not require FDA approval before marketing. [4]	NHS (page last reviewed 2022); NCCIH

Do the microbes settle in the gut?

ISAPP estimated that microbes from fermented foods can transiently make up 0.1% to 1% of bacteria in the large intestine. [1] The word "transiently" matters: a food bacterium passing through is not the same as a studied strain settling in. See do probiotic supplements colonize the gut.

What studies that compared a food with a capsule found

Why a trial result does not carry over

A supplement result is about a named strain and product. NCCIH says different types of probiotics may have different effects. [4]
A food result is about that food. Many fermented foods contain living microbes, some genetically similar to strains used as probiotics. [7] Similar is not the same as the same strain at a tested amount.
Shop products differ from trial products. The NHS says there is likely to be a huge difference between the pharmaceutical-grade probiotics that show promise in trials and the yoghurts and supplements sold in shops. [5]

Neither is a universal winner in the sources we read. For the trial evidence on fermented foods, see fermented foods evidence. For food pages, see probiotics, prebiotics and fermented foods.

Official intake levels

The sources we read do not describe an official recommended intake for probiotics or for fermented foods as a group.

Frequently asked questions

Do fermented foods count as probiotics?

Not automatically. The ISAPP panel said fermented foods are not equivalent to probiotic foods. [1]

Does yogurt contain probiotics?

It depends on the product. ISAPP says a food should be labelled "contains probiotics" only when its strains are defined to the strain level and present in adequate numbers. [1]

Is a food or a capsule better?

Proper evidence not found. We read one randomized crossover trial of a single strain in healthy adults, which found no significant difference in overall gut microbiota between yogurt smoothie and capsule. [6]

Can I use a fermented food instead of a probiotic my clinician recommended?

We do not give personal advice. Ask the clinician or pharmacist, because a result for one product does not carry over to a food. [4]

Are fermented foods safe for everyone?

No. Pasteurization status, listeria, histamine and salt matter for some people. For example, the FDA says people with weakened immune systems should not eat unpasteurized milk products. [8]

More details: evidence, limits and cautions

The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.

How to read the evidence labels

Labels used on this page: limited means few small studies, insufficient means too little to judge.

Study	What was compared	What was found	Strength
Healthy adults, mSphere 2021	One strain, Bifidobacterium animalis subsp. lactis BB-12, at about log10 10 ± 0.5 CFU per day, in a yogurt smoothie or a capsule. [6] The trial randomized 36 adults to four treatments. [6]	Neither form significantly changed the overall gut microbiota, gut transit time or stool short-chain fatty acids. [6] Daily BB-12 in the smoothie may have given a higher relative abundance of B. animalis. [6]	Limited. One strain, healthy adults, microbiome markers rather than symptoms

Proper evidence not found: we searched PubMed for trials that compared a fermented food directly with a probiotic supplement on symptoms or illness (terms such as yogurt versus capsule, kefir versus supplement, fermented milk versus probiotic). The only direct comparison we read is the one above. That study's authors said little research has examined the effect of the delivery matrix in humans. [6]

Safety and who should ask first

The risk of harm from probiotics is greater in people with severe illness or compromised immune systems. [4] The NHS advises talking to a doctor before taking probiotic supplements if you have an existing health condition or a weakened immune system. [5] Fermented foods carry their own cautions (listeria, histamine, salt), covered in fermented foods safety. Pregnancy, children, kidney or liver disease, medicine interactions and surgery are not addressed in the sources used for this page; ask a clinician or pharmacist. See probiotic safety and medication interactions.

References

Marco ML et al. The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on fermented foods. Nat Rev Gastroenterol Hepatol 2021;18:196-208 (PMID 33398112). Read 2026-10-23.
Marco ML et al. ISAPP consensus statement on fermented foods, abstract. Nat Rev Gastroenterol Hepatol 2021. Read 2026-10-23.
Hill C et al. The ISAPP consensus statement on the scope and appropriate use of the term probiotic. Nat Rev Gastroenterol Hepatol 2014 (PMID 24912386). Read 2026-10-23.
NCCIH (US National Center for Complementary and Integrative Health). Probiotics: Usefulness and Safety. Read 2026-10-23.
NHS (UK). Probiotics. Page last reviewed 24 November 2022. Read 2026-10-23.
Matrix effects on the delivery efficacy of Bifidobacterium animalis subsp. lactis BB-12 on fecal microbiota, gut transit time, and short-chain fatty acids in healthy young adults. mSphere 2021 (PMID 34232082). Read 2026-10-23.
Marco ML et al. Health benefits of fermented foods: microbiota and beyond. Curr Opin Biotechnol 2017 (PMID 27998788). Read 2026-10-23.
US Food and Drug Administration. Listeria (Listeriosis). Content current as of 16 January 2025. Read 2026-10-23.

Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.