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Head-to-head evidence comparison — which supplement is right for you?
B. lactis (BB-12 / HN019) vs Iron: Iron has the stronger overall evidence (9 vs 6/10); they're alternatives for support immune system — the best pick depends on your goals. 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
Too few graded studies
Top outcomes
Verdict
Likely helps
6 of 8 studies with measurable effects showed benefit.
Top outcomes
1-10 billion CFU daily for BB-12 (1 billion is enough); 10-20 billion CFU daily for HN019 if transit is the goal
Any time of day
Capsule or sachet standardized to a named strain (BB-12 or HN019)
18-40mg elemental iron for deficiency (varies by severity) (a typical label dose, not the dose used in the cited trials, which used 60 to 120 mg a day)
On empty stomach if tolerated, Away from tea, coffee, dairy
Ferrous bisglycinate (gentle, well-absorbed) or iron protein succinylate
and 6 more not shown
2 weeks
4 weeks
n/a
n/a
2-4 weeks
4-8 weeks
4-12 weeks
Dose-response effect of Bifidobacterium lactis HN019 on whole gut transit time and functional gastrointestinal symptoms in adults.
Scand J Gastroenterol (2011) · Rct · n=100
Whole-gut transit fell 49 to 21 hours on high dose (p<0.001) and 60 to 41 hours on low dose (p=0.01); placebo unchanged
Eight-Week Supplementation With Bifidobacterium lactis HN019 and Functional Constipation: A Randomized Clinical Trial.
JAMA Netw Open (2024) · Rct · n=229
Primary outcome (change in complete spontaneous bowel movements per week): +0.80 with HN019 vs +0.66 placebo — no difference
Effects of 28-day Bifidobacterium animalis subsp. lactis HN019 supplementation on colonic transit time and gastrointestinal symptoms in adults with functional constipation: A double-blind, randomized, placebo-controlled, and dose-ranging trial.
Gut Microbes (2018) · Rct · n=228
No significant differences vs placebo in the primary outcome (colonic transit time) or any secondary outcome
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=1376204
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=4558
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).
Iron has a higher evidence score (9/10 vs 6/10) and wins in 2 of 3 categories.
For support immune system, B. lactis (BB-12 / HN019) has a higher relevance score (32 vs 20).
No documented interaction was found in the data searched. This does not establish that this exact combination is safe.
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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.