Iodised salt for preventing iodine deficiency disorders.

Systematic review of trials in iodine-deficient populations, including children, adults, women of childbearing age, and pregnant women. Studies were conducted in diverse settings across both high-income and low-income countries, including Germany, South Africa, Italy, China, Sarawak, and the Himalayan endemic goitre belt in Punjab.

The review evaluated iodised salt for prevention of iodine deficiency disorders, compared with placebo or other iodine supplementation strategies. Across included trials, iodised salt formulations delivered roughly 12 to 53 ppm iodine, including potassium iodide and potassium iodate preparations; one arm used market iodised salt plus oral iodised oil 400 mg.

Iodised salt improved iodine status and was an effective preventive strategy for iodine deficiency disorders. The clearest reported benefit was on biochemical iodine status, including urinary iodine excretion, while evidence was insufficient to determine effects on physical or mental development or mortality. Adverse effects were not clearly shown, but safety data were limited. High-quality long-term trials are still needed to define optimal dosing and the best supplementation strategy across populations.

Evidence was limited by heterogeneous salt formulations and iodine doses, varied populations and settings, and a mix of small trials with one very large study. Most included outcomes were surrogate or disease-focused rather than patient-centered, and data on adverse effects, development, and mortality were sparse. The review also could not identify the optimal dose or the best strategy for different groups.