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Lactiplantibacillus plantarum 299v (DSM 9843)
The one probiotic strain with a genuinely distinctive trick: taken with a meal it increases non-heme iron absorption by roughly 50%, replicated across independent dual-isotope studies. Its IBS evidence is far weaker — rated low certainty, with one clearly negative trial — and it does not fix iron deficiency on its own.
What the evidence says
Most L. plantarum 299v studies are mechanism or observational rather than RCTs that measure a clinical effect — keep findings provisional.
Most evidence is from medium-quality meta-analyses and randomised trials published 2001–2024 with a typical study size of 79 participants.
Based on 12 studies · 2 meta-analyses · 8 RCTs · 1,250 total participants
Confidence
High confidenceBy outcome
The iron-absorption effect is replicated across independent dual-isotope studies and pooled in a dedicated meta-analysis, which is real — but the trials are tiny with no dose-response, the IBS evidence is rated low certainty, and the two best hard-outcome tests (paediatric ferritin, colonic fermentation) were both negative.
1 trial ongoing or recruiting · 4 completed on ClinicalTrials.gov
Registered trials show research momentum for L. plantarum 299v, not proof of effect — a registration is a plan, and posted results are sponsor-reported, not peer-reviewed. They are never counted toward the evidence rating above.
Browse these trials on ClinicalTrials.govClinicalTrials.gov · as of Sep 2026
Under EU law (Reg. 1924/2006), EFSA reviews whether a specific health claim for L. plantarum 299v meets the evidence standard. These are independent regulatory decisions on claims — not studies, and never counted toward the evidence score above.
Not authorised by EFSA
“Lactobacillus plantarum 299v Probiotic - reduces flatulences/ bloating”
“Lactobacillus plantarum 299v (DSM 9843) Supports your natural/body defence”
“Lactobacillus plantarum 299v (DSM 9843) Supports a healthy intestinal flora”
“Lactobacillus plantarum 299v (DSM 9843) Antioxidants that protect your body´s cells”
“Not authorised” means the specific claim wording did not meet the EU’s evidence standard — often a matter of dossier or phrasing, not proof of no effect. EFSA judges marketing claims and is kept separate from our study-based evidence score.
Source: EU Register of nutrition and health claims (European Commission / EFSA) · register snapshot Feb 2013
Our research database did not respond in time, so the studies and count above cover only our curated set. This refreshes automatically.
Lactiplantibacillus plantarum 299v (DSM 9843) is unusual among probiotics in having a well-replicated, mechanistically specific effect that has nothing to do with digestion comfort: it increases absorption of non-heme iron from a meal eaten at the same time.
Dual-isotope studies using whole-body counting found roughly 50% higher fractional absorption, and a dedicated meta-analysis of 8 studies pooled a moderate effect.
A large pregnancy RCT (n=326) found that pairing the strain with a low iron dose — 4.2 mg per serving taken twice daily, so 8.4 mg/day, still far below typical prenatal iron — reduced iron deficiency from 78% to 59% and iron-deficiency anaemia from 21% to 7.4% by week 35 — though that was a combination product, so the strain's independent contribution is unresolved.
The limits are real. The absorption trials are small (n=10-28) with a flat dose-response, and a ~50% rise in fractional absorption of a 5 mg iron dose amounts to a few hundred micrograms a day.
Crucially, it is an absorption ENHANCER, not iron: a randomised trial in iron-deficient children found it added nothing to ferrous sulfate.
For IBS the current Gastroenterology meta-analysis rates the evidence low certainty, one crossover trial found no symptom benefit and no change in overall colonic fermentation, and the eye-catching early results (100% vs 55% pain resolution in a 40-person trial) are too large to be credible.
Meals containing this strain showed increased ferric iron, and in intestinal cell co-cultures the ferric reductase DCYTB was upregulated — acting on iron's oxidation state and its reduction step at the gut wall, upstream of uptake.
Fermentation lowers pH and raises lactic acid, reducing phytate-to-mineral ratios and increasing mineral accessibility. Contributory but not sufficient — adding the strain to a heat-inactivated gruel did not raise absorption, so the food matrix matters.
Isolated from healthy human intestinal mucosa, survives transit, and adheres to mannose residues on the gut lining. It was recovered on rectal biopsies of treated patients, confirming it reaches the target site.
How L. plantarum 299v works — from molecular targets to health outcomes. Click an edge to see supporting research.This visualization is in beta — pathways are being refined and expanded.
The best pregnancy safety dataset of any strain here — 326 women dosed from week 10-12 to delivery, with adverse events, gestational length and birthweight comparable to placebo.
Well tolerated but ineffective for this purpose — it did not improve on ferrous sulfate alone.
Standard live-probiotic caution applies; no strain-specific case data exists either way.
A beneficial interaction rather than a hazard — it increases absorption and, in one 295-patient open-label (non-placebo-controlled) trial, substantially reduced the gut side effects that cause people to abandon iron therapy.
Antibiotics reduce viability if taken at the same time. The strain does not confer antibiotic resistance.
Tip: Published trials report only mild gut effects without quantified rates; typically settles
L. plantarum 299v has an evidence score of 5/10 — moderate evidence based on 16 indexed studies, including 2 meta-analyses. The one probiotic strain with a genuinely distinctive trick: taken with a meal it increases non-heme iron absorption by roughly 50%, replicated across independent dual-isotope studies. Its IBS evidence is far weaker — rated low certainty, with one clearly negative trial — and it does not fix iron deficiency on its own. Representative study: PMID 37541528.
The commonly studied dose of L. plantarum 299v is 1 x 10^9 CFU (1 billion) daily taken WITH the iron-containing meal is sufficient for the iron effect — in the dual-isotope crossover trial 10^9 was significant (28.6% vs 18.5%, p<0.028) while 10^10 was NOT (29.1% vs 20.1%, p=0.080). The freeze-dried capsule and IBS trials used 1 x 10^10 CFU daily, and the pregnancy trial used 1 x 10^10 CFU twice daily (2 x 10^10 CFU/day). Individual needs vary — start at the lower end of the range and adjust based on how you respond.
The best time to take L. plantarum 299v is with meals. Take it with food. Every positive absorption study co-administered the strain with the iron-containing meal.
L. plantarum 299v is generally well-tolerated and considered safe for most healthy adults at recommended doses. Reported side effects are uncommon and include transient gas or bloating. Use caution if any of these apply to you: Immunocompromise or immunosuppression (class-level precaution for live probiotics); Critical illness or indwelling central venous catheter; Short-bowel syndrome or compromised gut barrier.
Probiotics
Likely helpsLive microorganisms where strain selection determines outcome — Lactobacillus and Bifidobacterium strains best studied for gut, immune, and mood.
L. casei Shirota
Mostly mechanism / observationalThe Yakult strain — the most-trialled single probiotic strain of the three psychobiotic-adjacent contenders, and a clear illustration of why trial size matters. The two largest trials (n=737 and n=359) were null on their primary endpoints. The positives cluster in smaller, Yakult-affiliated studies that compared fermented milk against plain milk.
Saccharomyces Boulardii
Likely helpsAntibiotic-resistant probiotic yeast that supports digestive regularity and gut flora during travel and antibiotic use.
VSL#3 / Visbiome
Mostly mechanism / observationalAn 8-strain blend dosed in the hundreds of billions to trillions of CFU per day — roughly 45 to 7,000 times a typical 1-10 billion CFU consumer probiotic — with the largest effect size in the probiotic literature for one narrow use: maintaining remission in chronic pouchitis after ulcerative colitis surgery. It is null for IBS and Crohn's — and since 2016 the brand name no longer reliably identifies the formulation that was studied.
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Reviewed by Dr. Baher Al Hakim · Last reviewed July 2026 · evidence from 12 studies · how we score · editorial policy
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.
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