Research synthesisLow evidenceSmall effect6 studies · 1 beneficial · 5 neutral · 0 harmful
Across 6 studies, the evidence is predominantly neutral (5 studies) with one beneficial finding showing a moderate effect. The single beneficial study reported lower vitamin B12 levels in vitiligo patients compared to controls (mean difference -0.951, p<0.05). Most studies focused on clinical populations (PKU, vitiligo, bariatric surgery, fibromyalgia, celiac disease, periodontitis) with no consistent dose or duration data available. Effect sizes were mostly small and not statistically significant.
- Studied populations: clinical populations with specific conditions (phenylketonuria, vitiligo, post-bariatric surgery, fibromyalgia, celiac disease, periodontitis)
Caveats: Many of the included studies did not reach statistical significance — effect may be smaller than the predominant direction suggests. Evidence base is small (only 6 studies) — conclusions should be considered preliminary. No studies reported on supplemental vitamin B12 dosing; the findings relate to observational differences in B12 levels across clinical populations rather than intervention effects.
Generated Jul 14, 2026