Different concentration of iodized salt for preventing iodine deficiency disorder: a systematic review

Abstract

Objective To assess the effectiveness of different concentration of iodized salt for preventing iodine deficiency disorders. Methods Using the principle and method of systematic review, we searched Cochrane Library(from 1994 to Mar. 2007), Medline(from 1966 to Mar. 2007), BA(from 1969 to Mar. 2007), PubMed(from 1950 to Mar. 2007), OC1D(from 1950 to Mar. 2007), ISI Web of Knowledge(from 1966 to Mar. 2007), Vip (from 1989 to Mar. 2007), Wanfang(from 1997 to Mar. 2007), CBMDisc(from 1978 to Mar. 2007) and CNKI(1994 to Mar. 2007) and hand searched 6 relevant Chinese journals, including Chinese Journal of Preventive Medicine, Chinese Journal of Endemiology, Chinese Journal of Epidemiology, Chinese Journal of Control of Endemic Disease, Endemic Diseases Bulletin and Modern Preventive Medicine. We screened the for eligible studies according to the inclusion and exclusion criteria to be rigorously evealuatecl descriptly and qualitatively. Results Thirteen studies were included, of which, the first six were intervention trials with comparison, including two community intervention trials, which classified all objects into different groups, using iodized salt at different concentration as intervention, four were RCTs with different intervention methods, compare the iodized salt with other intervention measures. Seven were cross-sectional studies, which analyzed the iodine nutrition of people after the concentration of iodized salt was lowered down. Because of different interventions in control groups and different outcome measures, it was difficult to perform recta-analysis, a descriptive analysis of the results was presented. Most studies showed that urinary iodine level decreased as the concentration of iodized salt went down gradually. When the concentration of iodized salt went down to the best level recommended, goiter rate decreased obviously. Conclusions Iodized salt was considered as the hest method of iodine supply to prevent iodine deficiency disorders. But effectiveness of preventing iodine deficiency disorders with various concentration of iodized salt is different. To lower the concentration of iodized salt properly can not only prevent iodine deficiency disorders but also reduce the side effect of excess iodine intake to the minimum. And it can also save a lot of iodine resource. Well-designed community-based intervention trials with large sample size are needed to confirm the effect of different concentration of iodized salt on preventing iodine deficiency disorder. Key words: Iodine; Deficiency diseases; Urine; Salts; Systematic review