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Head-to-head evidence comparison — which supplement is right for you?
Iron vs L. plantarum 299v: Iron has the stronger overall evidence (9 vs 5/10); they work on different things and are often used together, not either/or. Take the 60-second quiz for a pick tailored to your goals.
Iron wins 2 of 3 categories. Both are solid choices — the best pick depends on your specific goals.
Verdict
Likely helps
11 of 15 studies with measurable effects showed benefit.
Top outcomes
Verdict
Mostly mechanism / observational
Top outcomes
18-45mg elemental iron for deficiency (varies by severity)
On empty stomach if tolerated, Away from tea, coffee, dairy
Ferrous bisglycinate (gentle, well-absorbed) or iron protein succinylate
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)
with-meals
Freeze-dried capsule standardized to 299v (DSM 9843)
and 6 more not shown
More absorbed iron per milligram taken, with better tolerability — potentially allowing a lower iron dose. The tolerability finding comes from an open-label trial, so treat its size as provisional. Note it did NOT improve on ferrous sulfate alone in iron-deficient children.
Take with the same meal as the iron, not separated.
2-4 weeks
4-8 weeks
4-12 weeks
Immediate, per meal
12-25 weeks
4 weeks
n/a
Daily oral iron supplementation during pregnancy
The Cochrane database of systematic reviews (2024) · Meta analysis · n=48971
There is probably little to no difference in maternal death (2 versus 4 events, RR 0.57, 95% CI 0.12 to 2.69; 3 trials, 14,060 women; moderate-certainty evidence).
The Prevalence of Anemia among Pregnant Women in China: A Systematic Review and Meta-Analysis
Nutrients (2024) · Meta analysis · n=722
The results showed that the prevalence of anemia, ID, and IDA among pregnant women in China were 30.7% (95% CI: 26.6%, 34.7%), 45.6% (95% CI: 37.0%, 54.2%), and 17.3% (95% CI: 13.9%, 20.7%), respectively.
Treatment for women with postpartum iron deficiency anaemia
The Cochrane database of systematic reviews (2024) · Meta analysis · n=572
Intravenous iron versus oral iron supplementation The evidence is very uncertain about the effect of intravenous iron on mortality (risk ratio (RR) 2.95, 95% confidence interval (CI) 0.12 to 71.96; P = 0.51; I² = not applicable; 3 RCTs; 1 event; 572 women; very low-certainty evidence).
A Systematic Review and Meta-Analysis on the Effects of Probiotic Species on Iron Absorption and Iron Status.
Nutrients (2019) · Meta analysis
Pooled SMD 0.55 (95% CI 0.22-0.88, p=0.001) for increased iron absorption across 8 studies
The effect of Lactiplantibacillus plantarum 299v together with a low dose of iron on iron status in healthy pregnant women: A randomized clinical trial.
Acta Obstet Gynecol Scand (2021) · Rct · n=326
Iron deficiency at week 35: 59% vs 78% (p=0.017); iron-deficiency anaemia 7.4% vs 21% (p=0.023)
Efficacy of Probiotics in Irritable Bowel Syndrome: Systematic Review and Meta-analysis.
Gastroenterology (2023) · Meta analysis
For global IBS symptoms, certainty of evidence was LOW for this strain (moderate only for Escherichia strains)
Based on meta-analyses showing hemoglobin improvements of 2.01-5.30 g/dL in iron deficient populations. Higher doses show diminishing returns with increased GI side effects. Effectiveness varies significantly by baseline iron status and form used.
AI-estimated from published studies. Interpret as directional guidance.
Iron has a higher evidence score (9/10 vs 5/10) and wins in 2 of 3 categories.
For boost daily energy, Iron has a higher relevance score (90 vs 34).
Iron and L. plantarum 299v may work well together: More absorbed iron per milligram taken, with better tolerability — potentially allowing a lower iron dose. The tolerability finding comes from an open-label trial, so treat its size as provisional. Note it did NOT improve on ferrous sulfate alone in iron-deficient children. Take with the same meal as the iron, not separated.
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The right pick depends on your goals. Answer a few quick questions for a personalised recommendation — or dig into the full evidence on each.