Research synthesisModerate evidenceModerate effect4 studies · 4 beneficial · 0 neutral · 0 harmful
Across 4 studies, 3 reported statistically significant beneficial effects of Lactobacillus plantarum 299v on improving iron levels, with effect sizes ranging from small to large. The predominant effect size was moderate, supported by a large meta-analysis and two randomized controlled trials, though one study showed only a small effect. Effects were typically observed over a median study duration of 90 days, with most evidence coming from studies in pregnant women and adults with iron deficiency or at risk for it.
- Effective dose range: 10^10 colony forming units per day
- Studied populations: pregnant women, adults with iron deficiency anemia
Caveats: Available evidence is overwhelmingly positive — clinical literature in this area is subject to publication bias (null-result studies are less likely to be published or indexed). Evidence base is small (only 4 studies) — conclusions should be considered preliminary. Two studies did not specify dose; one was a small feasibility trial (N=20) with no reported significance. Effects appeared more pronounced in clinical populations with iron deficiency than in healthy pregnant women, where the effect was smaller.
Generated Jun 17, 2026