Iodised salt and iodine supplements for prenatal and postnatal growth: a rapid scoping of existing systematic reviews.
BACKGROUND
Iodine deficiency can adversely affect child development including stunted growth. However, the effect of iodine supplementation or fortification on prenatal and postnatal growth in children (<18 years) is unclear. We identified the potential need for a systematic review to contribute to the evidence base in this area. To avoid duplication and inform the need for a new systematic review and its protocol, we undertook a rapid scoping review of existing systematic reviews investigating the effect of iodised salt and iodine supplements on growth and other iodine-related outcomes.


METHODS
We searched TRIP and Epistemokinos (latest search date 15 December 2014). All English language systematic reviews reporting on the effect of iodine supplementation or fortification in any form, dose or regimen on any iodine-related health outcomes (including but not limited to growth) were included. Eligible systematic reviews could include experimental or observational studies in pregnant or lactating women or children to age 18. We tabulated the extracted data to capture the scope of questions addressed, including: author, publication year, most recent search date, participants, pre-specified treatment/exposure and comparator, pre-specified outcomes, outcomes relevant to our question and number and type of studies included. Methodological quality of included reviews was assessed using AMSTAR.


RESULTS
Nine hundred and seventy-six records were screened and 10 reviews included. Most studies were of moderate methodological quality. Outcomes included assessments of thyroid function, iodine deficiency disorders, mental development and growth. Populations studied included pregnant women, preterm infants and children into adulthood. Most reviews looked at direct iodine supplementation or fortification, though some reviews considered iodine status, including the relationship between iodine intake and iodine biomarkers. Although five reviews pre-specified inclusion of growth outcomes, none provided synthesised evidence on the effects of iodine supplementation or fortification on prenatal and postnatal somatic growth.


CONCLUSIONS
Our rapid scoping review demonstrates a gap in the evidence base with no existing, up-to-date systematic reviews on the effects of all forms of iodine supplementation/fortification in all of the relevant population groups on relevant growth and growth-related outcomes. A new systematic review examining this question will assist in addressing this gap.
Human Nutrition Laboratory, Institute of Food, Nutrition, and Health, ETH Zurich, LFV D 11.2, Schmelzbergstrasse 7, 8092, Zurich, Switzerland. jessica.farebrother@hest.ethz.ch.
Jessica
J
Farebrother
Centre for Evidence-Based Health Care, Faculty of Medicine and Health Sciences, Stellenbosch University, Stellenbosch, South Africa.
Celeste E
CE
Naude
Centre for Evidence-Based Health Care, Faculty of Medicine and Health Sciences, Stellenbosch University, Stellenbosch, South Africa.
Liesl
L
Nicol
Human Nutrition Laboratory, Institute of Food, Nutrition, and Health, ETH Zurich, LFV D 11.2, Schmelzbergstrasse 7, 8092, Zurich, Switzerland.
Maria
M
Andersson
Human Nutrition Laboratory, Institute of Food, Nutrition, and Health, ETH Zurich, LFV D 11.2, Schmelzbergstrasse 7, 8092, Zurich, Switzerland.
Michael B
MB
Zimmermann
D000293:Adolescent; D002648:Child; D002657:Child Development / Q000187:drug effects*; D002664:Child Nutritional Physiological Phenomena; D002675:Child, Preschool; D019587:Dietary Supplements; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007455:Iodine / Q000008:administration & dosage*; D007774:Lactation; D039382:Maternal Nutritional Physiological Phenomena; D015201:Meta-Analysis as Topic; D064887:Observational Studies as Topic; D011181:Postnatal Care; D011247:Pregnancy; D011295:Prenatal Care; D016032:Randomized Controlled Trials as Topic; D017673:Sodium Chloride, Dietary / Q000008:administration & dosage*; D000078202:Systematic Reviews as Topic
D017673:Sodium Chloride, Dietary; C034024:iodized salt; D007455:Iodine