The effect of sodium restriction on iodine prophylaxis: a review

Purpose: Sodium is essential to life. However, its dietary excess is detrimental to the cardiovascular system, and sodium restriction is a crucial step in cardiovascular prevention. Iodine deficiency has been fought worldwide for decades, and substantial success has been achieved introducing the use of iodine-enriched salt. Nevertheless, areas of iodine deficiency persist around the world, both in developing and industrialized countries, and a major concern affecting dietary sodium reduction programs is represented by a possible iodine intake deficiency. There are substantial differences in the source of alimentary iodine among countries, such as iodized salt added, household tap water, seafood, or salt employed in packaged food. It is clear that a sodium-restricted diet can induce differences in terms of iodine intake, depending on the country considered. Moreover, iodine status has undergone relevant changes in many countries in the last years. Methods: Systematic review of literature evidence about the possible effects of sodium restriction on population iodine status. Results: To date, the available results are conflicting, depending on country, salt iodization policy, as well as time frame of data collection. However, to ensure an optimal iodine supply by salt fortification, without exceeding the current recommendation by World Health Organization for salt intake, seems to be an achievable goal. Conclusion: A balanced approach may be obtained by an adequate iodine concentration in fortified salt and by promoting the availability of iodized salt for household consumption and food industry use. In this scenario, updated prospective studies are strongly needed.