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. 2022 Sep 2;13(6):2488–2518. doi: 10.1093/advances/nmac088

TABLE 1.

Eligibility criteria are based on the Population, Intervention, Comparison, Outcomes, and Study (PICOS) elements

Population(s)1 Children and adults who were generally healthy or who had symptoms related to excessive zinc intake
Interventions, exposures

  • Intake of zinc via supplements or foods (fortified and nonfortified)

  • Studies where zinc intake was not given were excluded

  • Studies where the effect of zinc intake could not be isolated were excluded
Comparator(s)

  • Higher zinc intake vs. lower or no zinc intake
Outcome Adverse effects included impact on:

  • Absorption/status of other minerals (e.g., copper, iron, etc.)

  • Hemoglobin, ferritin

  • Blood lipids

  • Immune function

  • Gastrointestinal function

  • DNA breaks/damage
Study designs

  • Intervention studies assessing effects of zinc intake. Including but not limited to: RCTs, crossover RCTs, non-RCTs, pre-post studies

  • Observational studies assessing effects of zinc intake. Including but not limited to: case-control, cohort studies, cross-sectional studies

  • Case reports of excess zinc intake

  • In vitro and animal studies were not included
1

Based on results of the scoping review and related discussions, the expert group concluded that the limited data available in children aged 0–36 mo would not be sufficient to identify ULs and therefore it was decided to expand the literature search to include studies in older children and adults. Data for older children and/or adults would be used (i.e., extrapolated) only if data obtained via the literature for children aged 0–36 mo were insufficient to identify ULs directly. RCT, randomized control trial, UL, upper limit.