title: Systematic review of the effects of iodised salt and iodine supplements on prenatal and postnatal growth: study protocol.
abstract: BACKGROUND
  Iodine is an essential micronutrient and component of the thyroid hormones. Sufficient ingestion of iodine is necessary for normal growth and development. If iodine requirements are not met, growth can be impaired. Salt iodisation and supplementation with iodine can prevent iodine deficiency disorders and stunted growth. No systematic review has yet collated the evidence linking iodine to growth. With an increased emphasis on stunting within the WHO Global Nutrition Targets for 2025, we propose a systematic review to address this question.
  
  
  METHODS
  We will undertake a systematic review, and if appropriate, meta-analyses, evaluating the effects of iodised salt or iodine supplements on prenatal and postnatal somatic growth, until age 18. We will search a number of databases, including MEDLINE, EMBASE, Web of Science, CINAHL, PsychINFO, the Cochrane Library, including the CENTRAL register of Controlled Trials and also the WHO library and ICTRP (International Clinical Trials Registry Platform), which includes the Clinicaltrials.gov repository. We will also search Wanfang Data and the China Knowledge Resource Integrated Database. Included studies must have compared exposure to iodised salt, iodine supplements or iodised oil, to placebo, non-iodised salt or no intervention. Primary outcomes will be continuous and categorical markers of prenatal and postnatal somatic growth. Secondary outcomes will cover further measures of growth, including growth rates and indirect markers of growth such as insulin-like growth factor-1 (IGF-1).
  
  
  BACKGROUND
  The systematic review will be published in a peer-reviewed journal, and will be sent directly to the WHO, United Nations Children's Fund, International Council for the Control of Iodine Deficiency Disorders and other stakeholders. The results generated from this systematic review will provide evidence to support future programme recommendations regarding iodine fortification or supplementation and child growth.
  
  
  BACKGROUND
  PROSPERO CRD42014012940.
authors.affiliation: Human Nutrition Laboratory, Institute of Food, Nutrition, and Health, ETH Zurich, Zurich, Switzerland.
authors.forename: Jessica
authors.initials: J
authors.lastname: Farebrother
authors.affiliation: Centre for Evidence-Based Health Care, Faculty of Medicine and Health Sciences, Stellenbosch University, Stellenbosch, South Africa.
authors.forename: Celeste E
authors.initials: CE
authors.lastname: Naude
authors.affiliation: Centre for Evidence-Based Health Care, Faculty of Medicine and Health Sciences, Stellenbosch University, Stellenbosch, South Africa.
authors.forename: Liesl
authors.initials: L
authors.lastname: Nicol
authors.affiliation: Department of Nutrition and Food Hygiene, School of Public Health, Tianjin Medical University, Tianjin, China.
authors.forename: Zhongna
authors.initials: Z
authors.lastname: Sang
authors.affiliation: Key Laboratory of Trace Element Nutrition of the Ministry of Health, National Institute of Nutrition and Food Safety, Chinese Centre for Disease Control and Prevention, Beijing, China.
authors.forename: Zhenyu
authors.initials: Z
authors.lastname: Yang
authors.affiliation: Human Nutrition Laboratory, Institute of Food, Nutrition, and Health, ETH Zurich, Zurich, Switzerland.
authors.forename: Maria
authors.initials: M
authors.lastname: Andersson
authors.affiliation: Faculty of Health Sciences, Centre of Excellence for Nutrition, North-West University, Potchefstroom, South Africa.
authors.forename: Pieter L
authors.initials: PL
authors.lastname: Jooste
authors.affiliation: Human Nutrition Laboratory, Institute of Food, Nutrition, and Health, ETH Zurich, Zurich, Switzerland.
authors.forename: Michael B
authors.initials: MB
authors.lastname: Zimmermann
mesh_terms: D019587:Dietary Supplements; D005260:Female; D006130:Growth Disorders / Q000178:diet therapy* / Q000209:etiology / Q000517:prevention & control; D013006:Growth Hormone / Q000378:metabolism*; D006801:Humans; D007228:Infant Nutrition Disorders / Q000178:diet therapy* / Q000209:etiology / Q000517:prevention & control; D007227:Infant Nutritional Physiological Phenomena; D007231:Infant, Newborn; D007455:Iodine / Q000008:administration & dosage / Q000172:deficiency / Q000494:pharmacology*; D018977:Micronutrients / Q000008:administration & dosage* / Q000172:deficiency; D010913:Pituitary-Adrenal System / Q000503:physiopathology; D011247:Pregnancy; D017673:Sodium Chloride, Dietary / Q000008:administration & dosage / Q000494:pharmacology*; D000078202:Systematic Reviews as Topic
chemical_list: D018977:Micronutrients; D017673:Sodium Chloride, Dietary; C034024:iodized salt; D013006:Growth Hormone; D007455:Iodine