Case Studies
L. plantarum 299v and Tolerance of Oral Iron Therapy: A Randomised Controlled Trial
Clinical Overview
Adults with newly diagnosed iron deficiency anaemia (IDA) at a Turkish tertiary hospital received oral ferrous fumarate 100 mg elemental Fe²⁺/day for 3 months, with or without Lactobacillus plantarum 299v (10¹⁰ CFU/day for 30 days). In 295 mostly female patients (96.3 %), adding L. plantarum 299v reduced gastrointestinal intolerance from 46.5 % to 13.0 % and early treatment discontinuation from 15.9 % to 3.6 %. At 3 months, the probiotic group showed greater increases in serum iron (Δ23.5 v. 8.0 μg/dl) and transferrin saturation (Δ8.2 v. 2.1 %), and a larger haemoglobin gain (Δ0.9 v. 0.4 g/dl).
Study Setting
The trial was conducted in a single tertiary internal medicine clinic in Antalya, Turkey, in a clinical (not community) setting. Participants were adults over 18 years, predominantly women, with newly diagnosed IDA defined by low ferritin or transferrin saturation and Hb < 12 g/dl. Patients with irritable bowel syndrome, inflammatory bowel disease, coeliac disease, untreated menometrorrhagia or haemorrhoids, prior iron replacement therapy or prior intolerance to oral iron were excluded. Iron exposure consisted of oral ferrous fumarate (100 mg elemental Fe²⁺ once daily) for 3 months, with L. plantarum 299v given only during the first 30 days in the probiotic arm.
Study Design and Methods
| Aspect | Details |
|---|---|
| Design | Prospective, randomised, non-placebo-controlled, parallel-group trial comparing iron replacement therapy (IRT) alone versus IRT plus L. plantarum 299v in adults with newly diagnosed IDA; simple computer-generated randomisation. Follow-up: 3 months. Sample size: 295 randomised; 259 with 3-month iron indices. |
| Metal measurement | Oral iron provided as ferrous sulphate preparation containing ferrous fumarate pellets (304.2 mg, equivalent to 100 mg elemental Fe²⁺) once daily for 3 months. Serum iron, ferritin, and total iron-binding capacity (TIBC) were measured using an automated chemical analyser; transferrin saturation (%) was calculated as serum iron/TIBC×100. Haemoglobin was measured on an automated haematology analyser. |
| Microbial component | Probiotic: Lactobacillus plantarum 299v, administered as 10¹⁰ CFU/day (Probest®) for 30 days starting with day 1 of IRT in the IRT-Pro group. No direct microbiome sequencing, culture, or qPCR was performed; microbial assessment was limited to probiotic exposure. |
| Clinical endpoints | Primary clinical outcomes were gastrointestinal intolerance symptoms (loss of appetite, nausea, vomiting, abdominal pain, diarrhoea, constipation, bloating) captured via a 7-item questionnaire at baseline, within 30 days, and over 3 months; and treatment discontinuation within 30 days and 3 months. Biological endpoints were changes in Hb, ferritin, serum iron, TIBC and transferrin saturation from baseline to month 3. |
Major Findings
The trial links a defined ferrous iron replacement regimen to probiotic-modulated gastrointestinal tolerance and systemic iron indices in IDA.
Patients receiving L. plantarum 299v with Fe²⁺ had markedly fewer new gastrointestinal symptoms, less treatment discontinuation, and greater improvement in iron status. Within 3 months, intolerance developed in 13.0 % of IRT-Pro versus 46.5 % of IRT-only patients, and discontinuation within 30 days fell from 15.9 % to 3.6 %. These tolerability gains coincided with larger increases in ferritin, serum iron, transferrin saturation, and Hb, despite slightly worse baseline iron stores in the probiotic arm. The first 30 days emerged as the critical window in which the probiotic influenced persistence with ferrous therapy, which then translated into better metallomic outcomes at 3 months.
| Findings | Details |
|---|---|
| GI intolerance | Any intolerance within 3 months: 46.5 % (IRT-only) vs 13.0 % (IRT-Pro), P < 0.001 (Table 1). Key symptom reductions in IRT-Pro: lower total rates of loss of appetite (0.8 % vs 6.8 %), nausea (3.8 % vs 17.4 %), abdominal pain (3.0 % vs 19.7 %), and bloating (8.3 % vs 24.2 %) (Table 2). |
| De novo symptoms under IRT | New-onset loss of appetite, nausea, abdominal pain, and constipation were significantly more frequent in IRT-only than IRT-Pro (e.g. new abdominal pain 15.2 % vs 0 %, P < 0.001) (Table 2). |
| Treatment discontinuation | Within 30 days, discontinuation occurred in 15.9 % of IRT-only vs 3.6 % of IRT-Pro patients (P < 0.001); NNT=3 to prevent one additional discontinuation (Table 1). Constipation, nausea, and abdominal pain were the leading symptoms among early discontinuers. |
| Iron status at 3 months | Serum iron: 76.0 (51.0–96.0) vs 60.0 (43.0–70.0) μg/dl, P < 0.001; transferrin saturation: 20.1 (12.5–28.5) vs 14.5 (10.5–19.0) %, P < 0.001 for IRT-Pro vs IRT-only (Table 3). |
| Change in stores and Hb | Median ferritin change: +13.0 vs +5.0 ng/ml; transferrin saturation change: +8.2 vs +2.1 percentage points; Hb change: +0.9 vs +0.4 g/dl, all favouring IRT-Pro (P < 0.001) (Table 3). |
Mechanistic Interpretation & Microbial Metallomics
Above mentioned findings suggest that L. plantarum 299v modulates host–microbe–iron interactions to enhance both tolerance and utilization of orally administered Fe²⁺.
| Concept | Implication |
|---|---|
| Residual unabsorbed ferrous iron drives GI side effects | By counteracting adverse effects of unabsorbed iron in the gut lumen, L. plantarum 299v may reduce mucosal irritation manifested as abdominal pain, bloating, and nausea, improving tolerability and persistence. |
| Probiotic-mediated iron redox conversion | The authors propose that L. plantarum 299v promotes reduction of dietary ferric iron (Fe³⁺) to absorbable ferrous iron (Fe²⁺), enhancing enterocyte uptake and explaining greater rises in ferritin, serum iron, and transferrin saturation despite similar dosing. |
| Mucin production and epithelial interface | Enhanced mucin production at the intestinal surface is suggested to improve iron uptake at the mucosa, aligning with improved biochemical indices in the probiotic group. |
| Immune modulation and hepcidin axis | Anti-inflammatory actions of L. plantarum 299v could suppress cytokine-driven hepcidin elevation, thereby facilitating Fe²⁺ export from enterocytes into plasma and improving systemic iron availability. |
| Microbiota composition and dysbiosis in IDA | Although not directly measured, the authors situate IDA within a framework of gut dysbiosis; a fermentative lactic acid bacterium may shift the microbiota milieu toward improved iron bioavailability and reduced intolerance. |
| Time-limited probiotic exposure | A 30-day probiotic course was sufficient to influence outcomes at 3 months, suggesting persistent microbiota or mucosal changes that outlast direct dosing. |
Limitations
This single-centre, predominantly female cohort with strict exclusion of patients with chronic gastrointestinal disease or known iron intolerance limits generalizability to broader IDA populations. The trial was non-placebo-controlled and unblinded, so expectation effects on symptom reporting cannot be excluded. Gastrointestinal outcomes relied on binary self-report without severity grading. Adherence was assessed only via persistence (discontinuation), not dose-taking fidelity.
Future perspectives
Future studies should test L. plantarum 299v or other defined strains in multi-centre, placebo-controlled trials that include men, patients with IBS or inflammatory bowel disease, and those with prior iron intolerance. Incorporating detailed adherence metrics, symptom severity scales, and extended follow-up would clarify durability of both tolerability and iron status gains. Parallel measurement of hepcidin, erythropoietin, erythroferrone, and inflammatory markers could connect clinical outcomes to iron-regulatory pathways. Inclusion of stool sampling for microbiome profiling and confirmation of probiotic colonization would concretely position L. plantarum 299v within microbial metallomics, linking Fe redox chemistry, community structure, and clinical response.
Key takeaways for Researchers and Clinicians
In adults with IDA treated at a Turkish tertiary clinic, adding L. plantarum 299v to standard oral ferrous iron (100 mg elemental Fe²⁺/day) for the first 30 days lowered gastrointestinal intolerance (13.0 % vs 46.5 %) and sharply reduced early discontinuation (3.6 % vs 15.9 %). Despite worse baseline ferritin and transferrin saturation, the probiotic arm achieved greater gains in serum iron, ferritin, transferrin saturation, and Hb at 3 months, indicating improved iron bioavailability and storage.
Methodologically, this study demonstrates that pairing defined probiotic exposure with precise iron status markers can sensitively capture metallomic benefits even without direct microbiome sequencing. Clinically, a short course of L. plantarum 299v appears to be a pragmatic adjunct to ferrous therapy for IDA, potentially reducing the need for intravenous iron or alternative regimens prompted by intolerance. Translationally, the work highlights microbial manipulation of Fe²⁺/Fe³⁺ handling in the gut as an actionable axis for future microbial metallomics interventions in anaemia care.
Citation
Koker G, Sahinturk Y, Ozcelik Koker G, Coskuner MA, Eren Durmus M, Catli MM, Cekin AH. Improved gastrointestinal tolerance and iron status via probiotic use in iron deficiency anaemia patients initiating oral iron replacement: a randomised controlled trial. British Journal of Nutrition. 2024;132:1308–1316. doi:10.1017/S0007114524002757