Collaboration to optimize dietary intakes of salt and iodine: a critical but overlooked public health issue.

Perspectives High dietary salt is considered to cause about 30% of cases of hypertension. 1 Globally, approximately one quarter of the adult population has hyperten-sion, a leading risk factor for premature death. By 2025 it will affect 1.56 billion adults in the world and more than 90% of those aged 80 years or more will develop hypertension. High salt intake is also linked to other important diseases (such as gastric cancer, obesity, kidney stones and osteoporosis). Based on its impact on blood pressure and gastric cancer, high dietary salt is estimated to be the seventh leading risk factor for premature death in the United States of America and the second leading risk factor in Chile. 2,3 High salt intake in low-income countries also has a similar burden of illness and disability. The World Health Organization has recommended reducing salt intake to less than 5 g per day (less than 2000 mg/day) in adult populations. 4 Mild-to-moderate iodine deficiency impairs cognitive and motor function and severe iodine deficiency causes hy-pothyroidism with marked mental and growth retardation. 5 The main strategy recommended by the World Health Organization (WHO), the United Nations Children's Fund (UNICEF) and the International Council for the Control of Iodine Deficiency Disorders (ICCIDD) for correction of iodine deficiency is universal salt iodization. 6 Salt iodiza-tion to prevent iodine deficiency is a major global public health triumph; it is estimated about 70% of the global population now has access to adequately iodized salt. 5 Salt is generally used as the vehicle for providing iodine because it is consumed by most of the population at fairly constant levels throughout the year and its taste and appearance is not affected by iodization. Salt iodization is a highly cost-effective intervention that can be used in low-resource settings. The estimated costs of salt iodization programmes are 0.02 United States dollars (US$) to US$ 0.05 per person per year, resulting in a cost of US$ 34–36 per disability-adjusted life year gained (i.e. the cost to avert one year lost due to ill-health, disability or early death caused by iodine deficiency). 5 Adverse effects of iodiza-tion of salt are uncommon, occur when natural dietary sources of iodine have been adequate and are limited to the rare occurrence of hyperthyroidism. 5 Currently recommended average levels of iodine added to salt are within the range of 20–40 mg/kg, based on an estimated average salt consumption of 5–10 g/day …