Written and medically reviewed by Dr Zeeshan Afzal (MBBS) — Medical Doctor & Medical Content Lead, Welzo
Evidence-based · Honest about what's proven and what isn't · UK-focused
Last updated: July 2026 · Reading time: ~9 minutes
Fourteen strains against one. It sounds like an uneven contest, and for IBS specifically it is — just not in the direction the numbers suggest. Our digestive health guides explain why strain count is such a poor guide, and the probiotics range and wider gut health supplements cover the in-stock options.
Table of contents
For diagnosed IBS, Alflorex has the better case — it contains Bifidobacterium longum 35624, the most extensively trialled probiotic strain in IBS specifically, tested in IBS patients measuring IBS symptoms.
For general daily gut support at good value, Bio-Kult is the stronger buy — 120 capsules for £38.03 works out at around 32p a day, and it's shelf stable, UK-made and reliably available.
They're answering different questions. One is a targeted intervention; the other is broad daily cover.
Alflorex is built around a single organism, B. longum 35624 (previously classified as B. infantis 35624), developed through academic research in Ireland.
Its key trial randomised 362 women with IBS to one of three doses or placebo. At the effective dose it significantly improved abdominal pain, bloating, bowel dysfunction, flatulence, straining and incomplete evacuation — and notably, a dose a hundred times higher performed no better than placebo.
It would be easy to dismiss the 14-strain approach, and that would be unfair.
For someone who wants a sensible daily probiotic and doesn't have a specific condition to target, that's a perfectly rational purchase.
The difficulty comes when you buy breadth expecting it to solve a specific problem.
Probiotic effects are strain-specific, and evidence does not stack. A blend of fourteen researched strains is not fourteen times as evidenced — it's an untested combination unless that specific blend has been trialled as a finished product.
There's also arithmetic. If a total potency figure is spread across fourteen organisms, the amount of any single one may fall well below the dose used in the trial that made it interesting. And unless per-strain quantities are published, you can't check. Full argument in single vs multi-strain probiotics.
This is specific to IBS and rarely comes up in brand comparisons, but it matters if you've tried probiotics and felt worse.
Some lactic acid bacteria produce histamine as a by-product of fermentation. Most people clear it without difficulty. A subset of people — including a meaningful proportion of those with IBS — tolerate histamine poorly, and can react to a probiotic with flushing, headache, bloating or worsened symptoms.
Seeking Health ProBiota HistaminX — £38.80 · 120 reviews · Available from Welzo. Formulated specifically to exclude histamine-producing strains. If you have IBS and have reacted badly to broad-spectrum probiotics before, this addresses a variable neither Bio-Kult nor Alflorex is designed around.
| Feature | Alflorex | Bio-Kult Everyday |
|---|---|---|
| Design | One named strain | Fourteen strains |
| Trialled in IBS patients | Yes — 362-patient RCT | Not as a blend |
| Can you attribute a reaction | Yes — one organism | No |
| Pack size | Monthly | 120 capsules — four months |
| Cost per day | Higher | ~32p |
| Refrigeration | Not required | Not required |
| Stocked at Welzo | No | Yes |
Being straightforward: we stock Bio-Kult but not Alflorex. Alflorex is widely available from UK pharmacies, and we'd rather say so than steer you somewhere convenient for us.
If you want the targeted approach from stock, there is one other strain with a proper randomised IBS trial behind it.
Jarrow Ideal Bowel Support 299v — £42.99 · 116 reviews · Available from Welzo. Built on Lp299v, which alongside 35624 is one of only two strains with a randomised trial in IBS patients — 214 participants, with significant improvements in pain and bloating over four weeks. See our L. plantarum guide.
Klaire Labs Ther-Biotic Complete — £50.63 (from £59.00) · 94 reviews · Available from Welzo. A practitioner-facing multi-strain formula combining Lactobacillus and Bifidobacterium species — the same broad-coverage logic as Bio-Kult, from a clinical-channel brand.
This outranks the product choice entirely.
IBS is diagnosed after other conditions have been considered — coeliac disease, inflammatory bowel disease and bowel cancer can all produce overlapping symptoms. A coeliac blood test and a faecal calprotectin test are commonly used to help distinguish them. See coeliac testing and calprotectin testing.
And for IBS, dietary approaches have stronger evidence than any probiotic — a low FODMAP diet delivered with a dietitian is the best-supported intervention. See low FODMAP diet and IBS types.
Both are well tolerated by most people. Wind and bloating in the first fortnight are common — but with IBS, symptoms getting worse is a reason to stop rather than persevere. See probiotic side effects.
Speak to a doctor before taking either if you
More in probiotics safety.
On labelling: probiotics carry no authorised health claim in GB or the EU. Both are sold as food supplements and cannot legally be marketed as treating IBS or any other condition.
These are not IBS symptoms — see your GP promptly:
Persistent bloating in women is also among the symptoms associated with ovarian cancer and should be assessed. See when to see a GP and bowel cancer screening.
For diagnosed IBS, Alflorex — it contains B. longum 35624, trialled in IBS patients measuring IBS symptoms. Bio-Kult is the better value for general daily support, but its 14-strain blend has not been trialled as a finished product in IBS.
Not for a specific condition. Evidence is strain-specific and doesn't stack, so a blend of researched strains isn't a researched blend. Breadth is a sensible hedge when you have no target, not a substitute for one.
Pack size. £38.03 buys 120 capsules — around four months at one a day, or roughly 32p a day, dropping further on multibuy.
No. It's widely available from UK pharmacies. We've said so rather than steering you to something we do stock.
Histamine is one likely explanation — some lactic acid bacteria produce it, and broad blends are more likely to include one. A low-histamine formulation, or a single strain you can attribute a reaction to, is the sensible next step.
There's no safety reason not to, but no logic in it either — you won't know which is doing anything, and you'll be paying twice.
At least four weeks. If symptoms are worsening rather than improving, stop rather than pushing through.
No. Dietary approaches, particularly a low FODMAP diet with a dietitian, have stronger evidence. A probiotic is a reasonable addition, not a first-line treatment.
No — it's formulated to be shelf stable, which makes it practical for travel and everyday storage.
Jarrow Ideal Bowel Support 299v at £42.99 contains Lp299v, the other strain with a randomised trial in IBS patients.
Medical disclaimer: This article is for general information and education only and does not constitute medical advice, diagnosis or treatment. Welzo stocks Bio-Kult and does not stock Alflorex; this is stated openly and the comparison has not been adjusted to suit our range. Food supplements are not a substitute for a varied and balanced diet, and are not intended to diagnose, treat, cure or prevent any disease, including IBS. Probiotic effects are strain-specific; evidence for individual strains does not transfer to blends containing them unless the blend itself has been studied. IBS is a clinical diagnosis made after excluding other conditions — coeliac disease, inflammatory bowel disease and bowel cancer can produce overlapping symptoms and require assessment. Blood in the stool, unexplained weight loss, anaemia, night-time symptoms, or a change in bowel habit lasting three weeks or more are not IBS symptoms and need prompt medical review. Probiotics should be discussed with a doctor if you are immunocompromised, have an indwelling venous line, have inflammatory bowel disease, or are pregnant or breastfeeding. Prices, review counts and availability are correct at the time of writing.
About the author
Dr Zeeshan Afzal (MBBS) is a practising medical doctor and Welzo's Medical Content Lead. He writes and reviews Welzo's health content to ensure it is accurate, evidence-based and aligned with current UK clinical guidance.
Ocijenjeno izvrsno s 26,523+ recenzija
100% jamstvo povratka novca
Naše jamstvo povrata novca osigurava da primite svoje predmete ili dobijete potpuni povrat novca.
