Are all probiotics the same?

No, and this is the single most important thing to understand. Probiotic effects are strain-specific. Lactobacillus rhamnosus GG has a different evidence profile from another L. rhamnosus strain, which is different from L. acidophilus, which is different from a Bifidobacterium. A label saying 'Lactobacillus blend, 50 billion CFU' tells you very little — the strain identifiers (e.g. 'GG', 'CNCM I-745', '35624') and trial-matched dose matter much more than CFU count or species name.

Does Yakult / Actimel actually work?

The strain in Yakult (L. casei Shirota) and Actimel (L. paracasei DN-114001) have been studied in trials with generally modest, mixed results for bowel regularity and immune markers. They are real probiotic products with adequate CFU counts and are unlikely to cause harm in healthy adults. They are not the evidence-led choice for specific conditions where single-strain RCT data exists, such as IBS (B. infantis 35624) or antibiotic-associated diarrhoea (LGG or S. boulardii). Both are also relatively high in added sugar.

Do I need to refrigerate probiotics?

It depends on the product. Most traditional Lactobacillus and Bifidobacterium products require refrigeration to maintain their CFU count through shelf life. Spore-based probiotics (Bacillus species) and many shelf-stable formulations are designed not to require refrigeration. Look at the label: any product claiming 'shelf-stable' or 'no refrigeration required' should disclose the manufacturing technology. For refrigerated products, check whether CFU counts are quoted 'at time of manufacture' or 'at end of shelf life' — only the latter is meaningful for what you actually consume.

Should I take probiotics with antibiotics?

There is reasonable evidence — supported by Cochrane reviews — that probiotics, specifically LGG and Saccharomyces boulardii, reduce the risk of antibiotic-associated diarrhoea, including C. difficile-associated diarrhoea, particularly in patients over 65 or with prior episodes. Take the probiotic two to four hours after each antibiotic dose to avoid direct contact. S. boulardii is a yeast and is unaffected by antibacterial antibiotics, which is a practical advantage. NICE acknowledges the evidence but does not yet routinely recommend probiotic co-prescription on the NHS. Speak to your GP or pharmacist if you are unsure.

What's the best probiotic for IBS?

Bifidobacterium infantis 35624 (now classified as B. longum 35624) at 1 billion CFU/day has the strongest single-strain RCT evidence (Whorwell et al. 2006). It is sold in the UK as Alflorex by PrecisionBiotics. NICE recommends a 12-week trial of any chosen probiotic at the manufacturer's dose, with discontinuation if there is no improvement. NICE explicitly notes the strain-specific nature of the evidence and does not endorse generic multi-strain products. Lactobacillus plantarum 299v also has moderate trial evidence in IBS.

Are spore-based probiotics better?

Not categorically. Spore-based probiotics (Bacillus coagulans, B. subtilis, B. clausii) survive gastric acid more reliably than vegetative cells and do not require refrigeration, which is a practical advantage. The clinical evidence base is younger and smaller than for established Lactobacillus and Bifidobacterium strains. B. coagulans has reasonable evidence in IBS and constipation trials. Whether spore-based probiotics are clinically superior to traditional refrigerated probiotics is unestablished. Choose based on the strain-and-condition match, not on the spore-versus-traditional marketing axis.

Probiotics UK: Strain-Specific Evidence (and Where the Hype Outruns the Data)

Nutripedia Research Team28 April 2026

Most generic UK probiotics with eight strains and 50 billion CFU on the label have no clinical evidence supporting their specific blend. The probiotic literature is strain-specific, condition-specific, and dose-specific — and the gap between what works in trials and what is sold on the high street is wider than you'd think.

Not medical advice

Nutripedia summarises published peer-reviewed research. This content is for informational purposes only and is not a substitute for professional medical advice. Product mentions are not endorsements.

Before You Read This

Nutripedia is a research librarian, not a doctor. Nothing on this page is medical advice. Consult a UK GP, NHS pharmacist, or registered dietitian before starting any supplement, especially if you are pregnant, breastfeeding, on medication, or managing a chronic condition. Probiotics are generally well tolerated in healthy people but should be used with particular caution in immunocompromised patients, people with central venous catheters, critically ill patients, premature infants, and those with short-bowel syndrome — case reports of bacteraemia and fungaemia exist in these populations. If you have a chronic gastrointestinal condition such as IBD, IBS, or coeliac disease, discuss probiotic use with your gastroenterologist or GP.

Our research is based on 139 peer-reviewed studies. View the full evidence database

Our Top Picks

All Picks — Ranked

Frequently Asked Questions

Sources

Nutripedia is an educational resource. Content is sourced from peer-reviewed studies and does not constitute medical advice. Product mentions are not endorsements. Consult a healthcare professional before starting any supplement.

Reviewed by

Archie Roberts

Founder, Nutripedia — ALDR Ltd

This page summarises published research from PubMed, NHS, EFSA, and SACN. It does not constitute medical advice; consult a qualified healthcare professional before changing any supplement regimen.

Last reviewed: 28 Apr 2026Methodology