A systematic review of 16 trials found that oral vitamin B12 supplementation effectively reduces deficiency and raises B12 concentrations in children , but shows little to no effect on height, cognitive function, motor development, or anemia [low-certainty evidence]. The clinical benefit remains unclear outside of correcting the deficiency itself.
This Cochrane systematic review examined 16 randomized controlled trials involving 4,083 children across 10 countries to assess whether vitamin B12 supplementation affects growth, cognition, and development. The trials varied substantially in duration (28 days to 31 months), dosing (0.9 to 150 micrograms per day), and participant age (2 days to 11 years). Nine trials with 2,391 children contributed to meta-analyses. The review separated findings into three comparison groups: B12 alone versus placebo, B12 alone versus no intervention, and B12 combined with other micronutrients versus the same formula without B12.
For vitamin B12 supplementation alone versus placebo, the evidence was direct but underwhelming. While supplementation clearly reduced vitamin B12 deficiency (56 fewer cases per 1,000 children; high-certainty evidence) and probably increased total B12 concentrations by an average of 68.5 pmol/L (moderate-certainty evidence), it showed little to no effect on the outcomes that matter clinically. There was no meaningful difference in height or length (low-certainty), no detectable improvement in cognitive function like attention (low-certainty), no benefit for motor skill development (low-certainty), and no reduction in anemia rates (low-certainty). When comparing B12 with other micronutrients against the same formula without B12, the pattern held: no differences in height, cognition, or developmental outcomes, and minimal difference in B12 status itself.
The certainty of evidence ranged from high (for deficiency reduction) to very low (for growth outcomes versus no intervention). Reviewers downgraded assessments for small sample sizes, inconsistency across studies, selective reporting bias, and measurement problems. Critically, most trials did not measure the outcomes of greatest clinical interest. Few studies reported anemia rates, virtually none reported adverse effects, and cognitive and developmental testing was sparse. One trial did extend follow-up to nine years, but this appears to have been the exception rather than the rule.
The review's conclusions are deliberately restrained: B12 supplementation corrects the biochemical deficiency but may have little to no effect on actual health outcomes like growth, cognition, development, or anemia. The exception is when B12 is given alone rather than as part of a multinutrient package, where the biochemical correction is more pronounced. This distinction hints at possible interactions when B12 is combined with other nutrients, though the review does not elaborate on mechanisms.
The findings create a meaningful gap between biochemical correction and clinical benefit. If a child has confirmed vitamin B12 deficiency based on blood tests, supplementation will reliably raise B12 levels. Whether that correction translates to better growth, sharper thinking, or faster development remains unanswered by current evidence.
For children at risk of B12 deficiency, dietary sources should be the first consideration: animal products (meat, eggs, dairy), fortified plant-based foods, and breast milk supplementation for infants. The deficiency itself is worth treating based on its role in DNA synthesis and neurological function, but the evidence does not yet support supplementation as a growth or cognitive enhancer in children without deficiency.
For families considering B12 supplementation as part of a general children's multivitamin, this review suggests the addition of B12 to a formula containing other micronutrients may not substantially change outcomes compared to a formula without it, though the evidence quality is low. The dosing and delivery method matter: this review excluded injections and focused only on oral supplements, which means it does not address whether intramuscular B12 (sometimes used for severe deficiency) yields different results.
The absence of reported adverse effects across trials is reassuring, though the near-silence on safety data is itself a limitation. B12 has a high safety margin in most populations, but rigorous monitoring of side effects was not a primary focus of these studies.
| Parameter | Details |
|---|---|
| Study type | Systematic review and meta-analysis |
| Databases searched | CENTRAL, MEDLINE, Embase, 12 others; 2 trial registries |
| Included trials | 16 RCTs; 9 contributed to meta-analyses |
| Total participants | 4,083 children; age range 2 days to 11 years |
| Countries | India, Japan, Thailand, Nepal, United Kingdom, Italy, Spain, United States, El Salvador, Guatemala |
| Intervention duration | 28 days to 31 months |
| B12 doses | 0.9 to 150 micrograms per day |
| Follow-up | 5 weeks to 9 years (most 5 weeks to 31 months) |
| Critical outcomes | B12 status, anemia, hemoglobin, growth, cognitive function, development, adverse effects |
| Certainty assessment | GRADE methodology; high to very low certainty across outcomes |
| Funding | No dedicated funding |
| Published | The Cochrane Database of Systematic Reviews, 2025 |
Vitamin B12 supplementation for growth, development, and cognition in children. The Cochrane Database of Systematic Reviews. 2025. PubMed: 42227307
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