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Evidence-Based Supplement Research
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Vitamin B12 and Reduced Vitamin B12 Level

Research synthesisLow evidenceSmall effect5 studies · 1 beneficial · 4 neutral · 0 harmful

Across 5 studies, 4 found no significant difference in vitamin B12 levels between groups (neutral effect), while 1 study reported lower B12 levels in vitiligo patients (beneficial effect with moderate size). Effect sizes were predominantly small. Studies focused on clinical populations including patients with phenylketonuria, vitiligo, bariatric surgery, fibromyalgia, and periodontitis.

  • Studied populations: Clinical populations: PKU, vitiligo, bariatric surgery, fibromyalgia, periodontitis

Caveats: Many of the included studies did not reach statistical significance — effect may be smaller than the predominant direction suggests. Additionally, the evidence base is small (only 5 studies), and conclusions should be considered preliminary. No dose or duration data were consistently reported across studies.

Generated Jun 11, 2026
5 of 5 papers
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