Effect of salt reduction on iodine status assessed by 24 hour urinary iodine excretion in children and their families in northern China: a substudy of a cluster randomised controlled trial

Feng J He, Yuan Ma, Xiangxian Feng, Wanqi Zhang, Laixiang Lin, Xiaohui Guo, Jing Zhang, Wenyi Niu, Yangfeng Wu, Graham A MacGregor, Feng J He, Yuan Ma, Xiangxian Feng, Wanqi Zhang, Laixiang Lin, Xiaohui Guo, Jing Zhang, Wenyi Niu, Yangfeng Wu, Graham A MacGregor

Abstract

Objective: To study the effect of salt reduction on iodine status and to determine whether iodine consumption was still adequate after salt reduction in a population where universal salt iodisation is mandatory.

Design: A substudy of a cluster randomised controlled trial, with schools randomly assigned to either the intervention or the control group.

Setting: 28 primary schools in Changzhi, northern China.

Participants: 279 children in grade 5 of primary school (mean age: 10.1); 553 adults (age: 43.8).

Intervention: Children were educated about the harmful effects of salt and how to reduce salt intake using the schools' usual health education lessons. Children then delivered the message to their families. The duration was 1 school term (≈3.5 months).

Main outcome measure: Difference between the intervention and control groups in the change of iodine intake as measured by repeat 24 hour urinary iodine from baseline to the end of the trial.

Results: At baseline, the mean salt intake was 7.0±2.5 g/day in children and 11.7±4.4 g/day in adults and the median iodine intake was 165.1 μg/day (IQR: 122.6-216.7) and 280.7 μg/day (IQR: 205.1-380.9) in children and adults, respectively. At the end of the study, salt and iodine decreased in the intervention compared with control group. The mean effect on salt for intervention versus control was -1.9 g/day (95% CI -2.6 to -1.3) in children and -2.9 g/day (95% CI -3.7 to -2.2) in adults. The mean effect on iodine was -19.3% (95% CI -29.4% to -7.7%) in children and -11.4% (95% CI -20.3% to -1.5%) in adults.

Conclusions: With ≈25% reduction in salt intake, there was a significant reduction in iodine consumption in northern China where salt is iodised. Despite this, iodine intake was still adequate, and well above the estimated average requirement. Our findings indicate that reducing salt to the WHO's target-30% reduction by 2025-will not compromise iodine status.

Trial registration number: ClinicalTrials.gov NCT01821144.

Keywords: 24h urine collections; Cluster randomised trial; Iodine status; Salt reduction.

Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Figures

Figure 1
Figure 1
Mean salt, median iodine intake and their 95% CIs in children (A) and adults (B). EAR, estimated average requirement; RNI, recommended nutrient intake; UL, tolerable upper limit.

References

    1. WHO. Fortification of food-grade salt with iodine for the prevention and control of iodine deficiency disorders. Guideline, 2014. (accessed 27 Jan 2015).
    1. Ma T, Guo J, Wang F. The epidemiology of iodine-deficiency diseases in China. Am J Clin Nutr 1993;57(2 Suppl):264S–66S.
    1. Li S, Zheng Q, Xu J et al. . Iodine excess or not: analysis on the necessity of reducing the iodine content in edible salt based on the national monitoring results. Asia Pac J Clin Nutr 2011;20:501–6.
    1. Pearce EN, Andersson M, Zimmermann MB. Global iodine nutrition: where do we stand in 2013? Thyroid 2013;23:523–8. 10.1089/thy.2013.0128
    1. Teng W, Shan Z, Teng X et al. . Effect of iodine intake on thyroid diseases in China. N Engl J Med 2006;354:2783–93. 10.1056/NEJMoa054022
    1. Sang Z, Wang PP, Yao Z et al. . Exploration of the safe upper level of iodine intake in euthyroid Chinese adults: a randomized double-blind trial. Am J Clin Nutr 2012;95:367–73. 10.3945/ajcn.111.028001
    1. He FJ, MacGregor GA. Reducing population salt intake worldwide: from evidence to implementation. Prog Cardiovasc Dis 2010;52:363–82. 10.1016/j.pcad.2009.12.006
    1. Asaria P, Chisholm D, Mathers C et al. . Chronic disease prevention: health effects and financial costs of strategies to reduce salt intake and control tobacco use. Lancet 2007;370:2044–53. 10.1016/S0140-6736(07)61698-5
    1. National Institute for Health and Clinical Excellence (NICE). Guidance on the prevention of cardiovascular disease at the population level.
    1. WHO issues new guidance on dietary salt and potassium, 31 Jan 2013.
    1. Nath SK, Moinier B, Thuillier F et al. . Urinary excretion of iodide and fluoride from supplemented food grade salt. Int J Vitam Nutr Res 1992;62:66–72.
    1. Jahreis G, Hausmann W, Kiessling G et al. . Bioavailability of iodine from normal diets rich in dairy products—results of balance studies in women. Exp Clin Endocrinol Diabetes 2001;109:163–7. 10.1055/s-2001-14840
    1. He FJ, Wu Y, Ma J et al. . A school-based education programme to reduce salt intake in children and their families (School-EduSalt): protocol of a cluster randomised controlled trial. BMJ Open 2013;3:e003388.
    1. He FJ, Wu Y, Feng XX et al. . School based education programme to reduce salt intake in children and their families (School-EduSalt): cluster randomised controlled trial. BMJ 2015;350:h770 10.1136/bmj.h770
    1. He FJ, Ma Y, Feng X et al. . Effect of salt reduction on iodine status in children and their families in northern China: a sub-study of a cluster-randomised controlled trial. Lancet 2015;386:34.
    1. Centres for Disease Control and Prevention (CDC). The challenge of iodine deficiency disorder. A decade of CDC's ensuring the quality of urinary iodine procedures program. (accessed 30 Jan 2015).
    1. Zhang Y, Yan Y, Liu L et al. . Revised method with low usage amount of arsenic trioxide for testing urinary iodine by As (III)-Ce4+ catalytic spectrophotometry using ammonium persulfate digestion. Chin J Endemiol 2013;32:95–100.
    1. Chinese Nutrition Society. Chinese dietary reference intakes 2013. Beijing: Science Press, 2014. ISBN 978-7-03-041401-4.
    1. Carpenter JR, Kenward MG. Missing data in randomised controlled trials—a practical guide. London School of Hygiene, 2007. (accessed 14 Jun 2016).
    1. Zimmermann MB, Andersson M. Assessment of iodine nutrition in populations: past, present, and future. Nutr Rev 2012;70:553–70. 10.1111/j.1753-4887.2012.00528.x
    1. WHO/PAHO Regional Expert Group for Cardiovascular Disease Prevention through Population-wide Dietary Salt Reduction. Protocol for population level of sodium determination in 24-hour urine samples. (accessed 21 Jul 2015).
    1. People's Republic of China National Standard. National food safety standards—iodine content in salt. GB 26878—2011. (accessed 9 Apr 2015).
    1. Guo WP, Chen CS, Duan HY. Analysis of urinary iodine result of 1208 children in Changzhi. Chin J Health Lab Technol 2010;5:1173–4.
    1. Wu Y, Li X, Chang S et al. . Variable iodine intake persists in the context of universal salt iodization in China. J Nutr 2012;142:1728–34. 10.3945/jn.112.157982
    1. Song X, Li F, Liu Z et al. . [Assessment of dietary iodine intake of population in non-high-iodine areas in China]. Wei Sheng Yan Jiu 2011;40:138–41.
    1. Campbell NR, Dary O, Cappuccio FP et al. . Need for coordinated programs to improve global health by optimizing salt and iodine intake. Rev Panam Salud Publ 2012;32:281–6. 10.1590/S1020-49892012001000006

Source: PubMed

Sponsorer og samarbejdspartnere

Medicinske tilstande

Narkotikainterventioner

3
Abonner