This systematic review and the corresponding meta-analyses provide the first comprehensive synthesis of available data comparing consumption of, or exposure to, iodized salt on an entire array of iodine deficiency disorders, including goitre, urinary iodine excretion, cretinism, cognitive function and potential adverse effects such as hypothyroidism and hyperthyroidism.

Because this review comprised diverse study designs, including randomized controlled trials, non-randomized controlled trials, quasi-experimental, cohort observational, and multiple cross-sectional studies, the study was large enough to explore the effectiveness of iodized salt for preventing iodine deficiency disorders by a number of subgroups, such as age, physiological status, concentration of iodine in the salt, and risk of iodine deficiency disorders at baseline.

The additional information on the large number of outcomes and on potential effect modifiers provides important information for assessing and informing an update of the current WHO guidelines on salt iodization, especially in the context of renewed efforts to reduce salt consumption globally.