What Foods Contain Lactobacillus Reuteri? Sourdough, Kefir and More

Lactobacillus reuteri turns up in a few fermented foods: most reliably in home-fermented reuteri yoghurt made from a culture, sometimes in sourdough starters and in some kefirs and cheeses, but almost no supermarket product states it on the label. The trials that measured an effect used a defined strain at a stated dose, which no food can promise. This page is one spoke of the Wellgard probiotics guide.

Evidence at a glance

• Trials: two pooled analyses of infant colic (32 trials, 2,242 babies), two adult bone trials (90 and 239 women), one stool-tracking study (117 people).
• Largest single trial: 239 women aged 50 to 60, two years, one L. reuteri strain against placebo.
• Strongest measured outcome: daily crying in colicky babies, 64.7 minutes less with one L. reuteri strain; 74.3 minutes less in exclusively breastfed babies across all the cultures pooled.
• Not tested: what eating any food that contains L. reuteri does, home-made reuteri yoghurt included.

Sources checked on 12 October 2026.

What is Lactobacillus reuteri?

Lactobacillus reuteri is a species of lactic acid bacteria found in the human gut, urinary tract, skin and breast milk, and in many other mammals.¹ In 2020 the genus Lactobacillus, then 261 species, was split into 25 genera on whole-genome sequencing, so L. reuteri is now formally Limosilactobacillus reuteri; the bacterium and its trials are unchanged, and a label may carry either name.² One species is many strains, and a finding for one strain transfers neither to another nor to a food that carries the species. The trial record is on what Lactobacillus reuteri does.

Quick answer: which foods contain Lactobacillus reuteri?

The list is short and mostly "may contain", because the species is almost never named on a food label and no survey has counted it in UK shop products.^{1, 3}

• Contains it: home-made reuteri yoghurt, because you add the culture.
• Only if the label names it: yoghurts and fermented milk drinks that list L. reuteri as an added culture.
• May contain it: sourdough starter (not the baked loaf), some kefirs, some traditional and raw-milk cheeses, and raw sauerkraut, kimchi and miso, whose live bacteria go unnamed.^{3, 4}

Fresh fruit and vegetables are not on the list: raw produce carries the resident lactic acid bacteria that start a ferment such as sauerkraut, but no record we found names L. reuteri among them.⁴ More species, food by food: foods high in Lactobacillus.

Does yoghurt contain Lactobacillus reuteri?

Ordinary yoghurt does not, unless the maker has added it. Yoghurt is made with two starter cultures, Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus, and the one live-culture claim authorised for a food in Great Britain belongs to them: "live cultures in yoghurt or fermented milk improve lactose digestion of the product in individuals who have difficulty digesting lactose", conditioned on at least 100 million live cells per gram of those two cultures.⁵ It belongs to the yoghurt's own cultures, not to L. reuteri or to a capsule. A few "bio" or "live" yoghurts add L. reuteri; the ingredients panel is the only way to know. Greek yoghurt is defined by straining, not by its cultures; the same rule applies.

The full list of foods that may contain Lactobacillus reuteri

Live cultures survive only where nothing has killed them since fermentation; baking, cooking and pasteurising all do.⁴

Kefir and the other fermented drinks are compared on drinks with live cultures.

How to make Lactobacillus reuteri yoghurt at home

Home reuteri yoghurt is a long, warm ferment of milk started with a culture you add. The method people follow:

1. Stir a culture that names L. reuteri (an opened live-culture capsule or a bought starter) into pasteurised milk, or coconut milk for a dairy-free batch.
2. Add a spoonful of a fermentable fibre such as chicory inulin to feed the culture.
3. Hold it at a steady, warm temperature (roughly body heat) for a day or more, far longer than ordinary yoghurt takes.
4. Chill it, keeping some back to start the next batch.

It is a kitchen ferment, not a tested process: nobody has counted the live cells in a home batch, and no trial has measured what eating it does. Use clean equipment and fresh milk, refrigerate the result, and bin a batch that smells wrong. Nor is it for everyone. The groups the safety reviews single out are people with a weakened immune system, people who are seriously ill or in hospital with a central line, premature babies, and anyone whose doctor has said so: a few case reports describe bloodstream infections from live cultures in those groups, while in the large reviews of healthy people side effects were no more common than on placebo.⁶ In a 2021 Cochrane review of trials that gave live cultures in pregnancy to lower the chance of gestational diabetes, pre-eclampsia was more common in the women who took them, so speak to a midwife or GP before any supplement in pregnancy.⁷

How to increase Lactobacillus reuteri naturally

Live fermented foods raise the live cultures you swallow, and the capsule record suggests they pass through rather than settle. In a study that tracked one bifidobacterium strain in 117 people over eight weeks of capsules, stool levels rose while the capsules were taken and fell back towards baseline once dosing stopped; the authors call the stay transient.⁸ No food we found has been tracked this way, but the capsule study suggests the same: present while taken, not for good. Fibre-rich foods such as onions, garlic, leeks and oats feed gut bacteria generally; no trial on this page measured whether they raise L. reuteri.

Fermented foods vs supplements: which is more reliable?

Neither is ranked above the other; they answer different questions. A fermented food gives an unstated amount of whichever strains the batch grew; a capsule or drops state the species and a count, so a label can be matched to a trial. In a 2017 network analysis of 32 trials in 2,242 babies, one specific L. reuteri strain ranked ahead of every other intervention for crying time, and in a 2024 pooled analysis the same strain shortened crying by about an hour a day (64.7 minutes); across all the cultures pooled, exclusively breastfed babies cried 74.3 minutes less, with limited evidence in formula-fed and caesarean-born babies.^{9, 10} In adults, a 12-month trial in 90 women aged 75 to 80 found about 1% less loss of shin-bone density than placebo at 10 billion live cells a day, but a two-year trial of the same strain in 239 women aged 50 to 60 found no effect on bone loss.^{11, 12} A food cannot tell you whether it carries either strain, or how much.

What we don't know

• No trial has measured what eating home-made reuteri yoghurt, or any other food that carries L. reuteri, does to the gut or to any symptom.
• No survey has counted L. reuteri in UK shop yoghurt, kefir or cheese.
• No trial has compared a food source of L. reuteri with capsules or drops for any outcome.

Frequently asked questions

Is Lactobacillus reuteri in kefir?

Sometimes. Kefir grains vary in the bacteria and yeasts they hold, and labels rarely list species; unless the pack names L. reuteri, regard it as "may contain".

Does sourdough bread contain live Lactobacillus reuteri?

The starter may: L. reuteri was recovered from one industrial sourdough across ten years of propagation, a feature of some starters, not all.³ The baked loaf does not; oven heat kills live cultures.⁴

How much Lactobacillus reuteri is in food?

Nobody states it: food makers do not count or label the species, home batches are never measured, and amounts vary by batch. The colic trials gave a stated daily amount of one strain as drops and measured crying after 21 to 28 days.⁹

Can I get enough from food alone?

No trial has compared food with capsules or drops, so there is no "enough" to measure against; the measured effects came from defined strains at stated doses.⁹ The NHS page "Probiotics", last reviewed 24 November 2022 and past its own review date, says there is "little evidence to support many health claims made about them".¹³

Sources

1. Mu Q, Tavella VJ, Luo XM. Role of Lactobacillus reuteri in Human Health and Diseases. Narrative review, 2018. PubMed 29725324.
2. Zheng J, et al. A taxonomic note on the genus Lactobacillus: description of 23 novel genera, emended description of the genus Lactobacillus Beijerinck 1901, and union of Lactobacillaceae and Leuconostocaceae. Taxonomic study, 261 species, 2020. PubMed 32293557.
3. Gänzle MG, Vogel RF. Contribution of reutericyclin production to the stable persistence of Lactobacillus reuteri in an industrial sourdough fermentation. Laboratory study, one sourdough, 10 years, 2003. PubMed 12430769.
4. Marco ML, et al. The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on fermented foods. Expert consensus statement, 2021. PubMed 33398112.
5. EFSA Panel on Dietetic Products, Nutrition and Allergies. Scientific opinion on live yoghurt cultures and improved lactose digestion. Scientific opinion, 2010. doi:10.2903/j.efsa.2010.1763.
6. Doron S, Snydman DR. Risk and safety of probiotics. Safety review, 2015. PubMed 25922398.
7. Davidson SJ, et al. Cochrane review of live cultures given in pregnancy against gestational diabetes, 7 trials, 1,647 women; pre-eclampsia in 4 trials, 955 women, 2021. PubMed 33870484.
8. Charbonneau D, Gibb RD, Quigley EM. Fecal excretion of Bifidobacterium infantis 35624 and changes in fecal microbiota after eight weeks of oral supplementation with encapsulated probiotic. Stool-tracking trial, 117 people, 8 weeks, 2013. PubMed 23549409.
9. Gutiérrez-Castrellón P, et al. Efficacy of Lactobacillus reuteri DSM 17938 for infantile colic: systematic review with network meta-analysis. Network meta-analysis, 32 trials, 2,242 infants, 2017. PubMed 29390535.
10. Vaz SR, et al. Probiotics for infantile colic: is there evidence beyond doubt? A meta-analysis and systematic review. Pooled analysis of randomised trials in infants, 2024. PubMed 37962097.
11. Nilsson AG, et al. Lactobacillus reuteri reduces bone loss in older women with low bone mineral density: a randomized, placebo-controlled, double-blind, clinical trial. Randomised trial, 90 women, 12 months, 2018. PubMed 29926979.
12. Gregori G, et al. Limosilactobacillus reuteri 6475 and prevention of early postmenopausal bone loss: a randomized clinical trial. Randomised trial, 239 women, 2 years, 2024. PubMed 38865129.
13. NHS. Probiotics. Page last reviewed 24 November 2022 (review overdue). nhs.uk.

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