Table 1.

Population–intervention–comparison–outcome (PICOS) criteria for study inclusion and exclusion.

Criteria Category	Inclusion	Exclusion
Population	Adults (aged ≥ 18 y) residing in industrialised nations.	Individuals (aged < 18 y), unless results display separate data; adults residing in developing countries; populations with a high prevalence of thyroid disorders.
Intervention/exposure	Participants with any type of dietary preference or restriction. Voluntary or otherwise.	Use of a dietary grouping without defining diet characteristics.
Comparators	Differing dietary preference or restriction.	None.
Outcome measure	Iodine intake or status measured by UIC or analysis of dietary records.	No analysis of iodine intake or status; use of thyroid measures alone for iodine intake and status.
Study design	Any study design with relevant outcomes.	None.