Across 3 meta-analyses examining zinc levels in clinical populations, findings are mixed: 1 large beneficial effect (lower zinc in vitiligo patients), 1 small neutral effect (no significant difference after bariatric surgery), and 1 large harmful effect (lower zinc in MCI patients). The predominant effect size is mixed (small to large), and no consistent dose or form data is available. All studies are observational comparisons, not interventional trials, so the effect of zinc supplementation on reducing zinc levels is not directly tested.
Caveats: Evidence base is small (only 3 studies) — conclusions should be considered preliminary. All studies are observational meta-analyses comparing zinc levels in disease groups vs controls; no interventional data on zinc supplementation exists for this outcome. The direction of effect is inconsistent and may reflect disease-specific differences rather than supplement effects. No form or dose information is available to guide supplementation decisions.
zinc (MD, -0.642; 95% CI, -0.731--0.554; p <0.001) levels were lower in the vitiligo group than in the control group.
Deficiencies in key micronutrients such as vitamin D, vitamin B12, albumin, calcium, zinc and iron were reported across revision types.
Zn (SMD: -0.77, 95%CI: -1.22-0.33) were significantly lower