Probiotics

What It Does

The accepted definition is live microorganisms that confer a health benefit when given in adequate amounts (Hill 2014). Proposed mechanisms include competing with pathogens for space and nutrients, producing lactic acid and antimicrobial peptides, tightening the intestinal barrier, and signaling to immune cells, most of it shown in laboratory and animal work. Most strains do not colonize the adult gut. They are detectable in stool while you take them and disappear within days to weeks of stopping.

Antibiotic-associated diarrhea has the strongest evidence. A 2017 Cochrane review found that probiotics taken with antibiotics reduced C. difficile-associated diarrhea by about 60%, with the benefit concentrated where baseline risk was above 5% (Goldenberg 2017). In children, probiotics cut antibiotic-associated diarrhea from about 19% to 8%, and LGG and S. boulardii at 5-40 billion CFU a day were the best supported (Guo 2019). For S. boulardii specifically, a 2015 meta-analysis found the risk fell from about 19% to 9% (Szajewska 2015).

For IBS, some strains and combinations improve global symptoms, but the evidence is low quality and too fragmented to rank strains (Ford 2018). The most instructive trial tested B. longum 35624 in 362 women: 100 million CFU a day improved symptoms, and 10 billion CFU did not, probably because the high-dose capsule formulation clumped (Whorwell 2006). The American Gastroenterological Association recommends probiotics only within clinical trials for most GI conditions, with conditional exceptions for C. difficile prevention with specific strains, pouchitis, and preterm infants (Su 2020). In pouchitis, an eight-strain high-dose formulation kept 85% of patients in remission for nine months, against none on placebo (Gionchetti 2000).

More is not always better. After a course of antibiotics, an 11-strain probiotic delayed recovery of people's native gut bacteria compared with no treatment, in a small but carefully sampled study (Suez 2018).

Forms and Bioavailability

Absorption ratings are broad tiers. Head-to-head human trials rarely support a finer ranking among well-absorbed forms.

The strain designation is the letters and numbers after the species name: GG, CNCM I-745, DSM 17938, 35624. A product without one cannot be matched to a trial. In 2020 many Lactobacillus species were moved to new genera, so L. rhamnosus GG may appear as Lacticaseibacillus rhamnosus GG. CFU counts can be stated "at time of manufacture," which overstates what survives to the expiration date; look for a guarantee through expiration. Refrigerate if the label says to. Spore-forming Bacillus strains and the yeast S. boulardii are more shelf-stable than most lactobacilli and bifidobacteria.

Typical Dosing

Effective doses are specific to the strain and range from about 100 million to more than 100 billion CFU a day. Match the strain and dose to a trial for the condition you are treating.

Food sources: yogurt with live cultures, kefir, some aged cheeses, unpasteurized sauerkraut and kimchi.

What to Look For

Start with the reason, then pick the strain. With antibiotics, take LGG or S. boulardii from the first day of the course and for one to two weeks after. Bacterial probiotics should be taken a few hours apart from each antibiotic dose; S. boulardii can be taken at the same time. For IBS, a four-week trial of one evidence-backed strain is reasonable, and if nothing changes, stop. For pouchitis, use the formulation your gastroenterologist recommends; the original eight-strain formula is now sold as Visbiome, and products sold as VSL#3 after 2016 come from a different manufacturer.

People who are critically ill, immunocompromised, or have a central venous catheter should not take probiotics without their physician's approval. Preterm infants should receive them only under neonatal care.

Red flags: no strain designations, CFU counted at manufacture, "50 billion CFU, 10 strains" as the main selling point, and probiotic gummies or sodas. Green flags: strain IDs on the label, CFU guaranteed through expiration, and a product that matches a published trial.

Products on Titrate

The Probiotics category in Titrate's index holds 5,145 labels from the NIH Dietary Supplement Label Database, 2,852 of them currently on market, out of 214,745 labels indexed in total.

Top on-market labels, ranked by label completeness and simplicity:

1. Organic Probiotic Gripe Water Wellements · 0 NP
2. Probiotic Acidophilus with Pectin Nature's Measure · 0 NP
3. Soothe Vitamin D & Probiotic Drops Gerber Good Start · 0 NP
4. Probiotic Acidophilus with Pectin Meijer · 0 NP
5. Probiotic Acidophilus Schiff · 0 NP

Search probiotics supplements

Supplement Search loads one category at a time. Choose the Probiotics tab and filter by ingredient, form, or what the product leaves out.

Related Tools

• Bifidobacterium longum 35624 vs De Simone Formulation
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• Unstudied Multi-Strain Blends vs Saccharomyces boulardii
• All probiotics form comparisons
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References

NIH Office of Dietary Supplements. Probiotics: Fact Sheet for Health Professionals.

Gionchetti P, Rizzello F, Venturi A, et al. Oral bacteriotherapy as maintenance treatment in patients with chronic pouchitis: a double-blind, placebo-controlled trial. Gastroenterology. 2000;119(2):305-309.

Whorwell PJ, Altringer L, Morel J, et al. Efficacy of an encapsulated probiotic Bifidobacterium infantis 35624 in women with irritable bowel syndrome. Am J Gastroenterol. 2006;101(7):1581-1590.

Hill C, Guarner F, Reid G, et al. Expert consensus document: The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic. Nat Rev Gastroenterol Hepatol. 2014;11(8):506-514.

Szajewska H, Kołodziej M. Systematic review with meta-analysis: Saccharomyces boulardii in the prevention of antibiotic-associated diarrhoea. Aliment Pharmacol Ther. 2015;42(7):793-801.

Goldenberg JZ, Yap C, Lytvyn L, et al. Probiotics for the prevention of Clostridium difficile-associated diarrhea in adults and children. Cochrane Database Syst Rev. 2017;12(12):CD006095.

Suez J, Zmora N, Zilberman-Schapira G, et al. Post-antibiotic gut mucosal microbiome reconstitution is impaired by probiotics and improved by autologous FMT. Cell. 2018;174(6):1406-1423.

Ford AC, Harris LA, Lacy BE, Quigley EMM, Moayyedi P. Systematic review with meta-analysis: the efficacy of prebiotics, probiotics, synbiotics and antibiotics in irritable bowel syndrome. Aliment Pharmacol Ther. 2018;48(10):1044-1060.

Guo Q, Goldenberg JZ, Humphrey C, El Dib R, Johnston BC. Probiotics for the prevention of pediatric antibiotic-associated diarrhea. Cochrane Database Syst Rev. 2019;4(4):CD004827.

Su GL, Ko CW, Bercik P, et al. AGA clinical practice guidelines on the role of probiotics in the management of gastrointestinal disorders. Gastroenterology. 2020;159(2):697-705.