Iodised salt for preventing iodine deficiency disorders

  • Review
  • Intervention

Authors


Abstract

Background

Iodine deficiency is the main cause for potentially preventable mental retardation in childhood, as well as causing goitre and hypothyroidism in people of all ages. It is still prevalent in large parts of the world.

Objectives

To assess the effects of iodised salt in comparison with other forms of iodine supplementation or placebo in the prevention of iodine deficiency disorders.

Search methods

We searched The Cochrane Library, MEDLINE, the Register of Chinese trials developed by the Chinese Cochrane Centre, and the Chinese Med Database, China National knowledge Infrastructure, and searched reference lists, databases of ongoing trials and the Internet.

Selection criteria

We included prospective controlled studies of iodised salt versus other forms of iodine supplementation or placebo in people living in areas of iodine deficiency. Studies reported mainly goitre rates and urinary iodine excretion as outcome measures.

Data collection and analysis

The initial data selection and quality assessment of trials was done independently by two reviewers. Subsequently, after the scope of the review was slightly widened from including only randomised controlled trials to including non-randomised prospective comparative studies, a third reviewer repeated the trials selection and quality assessment. As the studies identified were not sufficiently similar and not of sufficient quality, we did not do a meta-analysis but summarised the data in a narrative format.

Main results

We found six prospective controlled trials relating to our question. Four of these were described as randomised controlled trials, one was a prospective controlled trial that did not specify allocation to comparison groups, and one was a repeated cross-sectional study comparing different interventions. Comparison interventions included non-iodised salt, iodised water, iodised oil, and salt iodisation with potassium iodide versus potassium iodate. Numbers of participants in the trials ranged from 35 to 334; over 20,000 people were included in the cross-sectional study. Three studies were in children only, two investigated both groups of children and adults and one investigated pregnant women. There was a tendency towards goitre reduction with iodised salt, although this was not significant in all studies. There was also an improved iodine status in most studies (except in small children in one of the studies), although urinary iodine excretion did not always reach the levels recommended by the WHO. None of the studies observed any adverse effects of iodised salt.

Authors' conclusions

The results suggest that iodised salt is an effective means of improving iodine status. No conclusions can be made about improvements in other, more patient-oriented outcomes, such as physical and mental development in children and mortality. None of the studies specifically investigated development of iodine-induced hyperthyroidism, which can be easily overlooked if just assessed on the basis of symptoms. High quality controlled studies investigating relevant long term outcome measures are needed to address questions of dosage and best means of iodine supplementation in different population groups and settings.

摘要

背景

加碘鹽(Iodised salt)用於預防碘缺乏(iodine deficiency disorders)疾病

碘缺乏是造成兒童可能可預防之智能遲緩的主要原因,且可在所有年齡層造成甲狀腺腫及甲狀腺低能症。甲狀腺腫(goitre)及甲狀腺低能症(hypothyroidism),這種病仍在世界大部分地區盛行。

目標

評估加碘鹽與其他形式的碘補充製劑或安慰劑在預防碘缺乏疾病的療效。

搜尋策略

我們搜尋The Cochrane Library, MEDLINE, the Register of Chinese trials developed by the Chinese Cochrane Centre, and the Chinese Med Database, China National knowledge Infrastructure及搜尋參考表,正在進行中的試驗資料庫及網路。

選擇標準

我們包括前膽性有控制組的研究,來比較加碘鹽與其他形式的碘補充製劑或安慰劑使用在居住於缺碘地區的人。研究主要是報告甲狀腺腫比率及碘的排泄的結果。

資料收集與分析

初始資料的收集及試驗的品質評估由二位審查個別進行,後來評論的範圍由只包含隨機控制試驗稍擴大至包括非隨機前膽比較性的研究,第三位審查再進行試驗的選擇及品質的評估。因為這些被選擇的研究沒有充分的同類性及品質。我們沒有做統合分析,只是把這些以直接敘示來做結論。

主要結論

我們發現6篇有前膽性及控制組的試驗涉及我們的問題,4篇研究是隨機抽樣且有控制組,一篇是前膽控制組試驗但無特別涉及比較組,另外一篇為比較不同試驗研究的橫斷面(crosssectional)研究。比較性的試驗試討包括無碘鹽、加碘水、碘化油及加碘化鉀的碘鹽(potassium iodate)或加碘酸鉀的碘鹽(potassium iodate),試驗的參加人數從35人到334人;超過20,000人被包括在這些橫斷面研究。三篇研究只涉及兒童,二篇探討包括兒童及成人,一篇探討懷孕婦女。加碘鹽對甲狀腺腫有減小的趨勢,雖然統計上無意義。大部分研究也顯示缺碘的狀況有改善(除了一篇有關較小兒童的研究),雖然尿液的碘排泄未達世界衛生組織WHO的建議標準。無任何研究觀察加碘鹽任何副作用。

作者結論

這些結果建議加碘鹽對改善碘狀況是一個有效的方法。至於其他方面的改善,如更多以病人為主體的結果,像在兒童,其身體及智能的發展及死亡率沒有結論。沒有研究特別針對碘引起的甲狀腺高能症,而這是很容易被忽略,如果我們只專注在症狀,有高品質及有控制組設計的研究,在不同族群及情況下,針對劑量及碘補充的最好方法,來調查相關的長期結果是需要的。

翻譯人

本摘要由慈濟醫院陳信典翻譯。

此翻譯計畫由臺灣國家衛生研究院(National Health Research Institutes, Taiwan)統籌。

總結

加碘鹽補充改善碘的狀況,但在其他方面的效果不清楚。碘缺乏在兒童造成智能退化及甲狀線腫,在各年齡層造成甲狀腺激素缺乏。這種現像仍存在世界各地,這篇回顧省視飲食中加碘鹽的研究,包含了比較組的設計。六篇包含的研究大部分在兒童進行,一些則在成人進行。尿液中的碘在所有的研究都顯示增加,只有一篇例外,可能是較少兒童不能吃下足夠的鹽來達到足夠的碘狀況。一些研究,不是全部,同時顯示可減少因飲食中缺碘所造成的甲狀腺腫大。沒有副作用報告,可能是沒有被充分的探討。更佳品質且長期的研究來控討有關兒童的發育,缺碘所造成的死亡及藥物的副作用是需要的。

Plain language summary

Iodised salt for preventing iodine deficiency disorders

Iodine deficiency causes mental retardation in children as well as enlarged thyroid glands (goitre) and deficiencies in thyroid hormones in people of all ages. It still exists in large parts of the world. This review looked at studies of iodised salt in the diet that included a comparison group. Six studies, most of them in children but some also in adults, were included. Iodine in the urine increased in all but one studies, but there was some concern that small children did not eat enough salt to achieve adequate iodine status. Some studies, but not all, also showed a reduction in the enlargement of the thyroid gland (goitre) that can accompany lack of iodine in the diet. Adverse effects were not reported, but these may not have been studied adequately. More high quality long term studies measuring outcomes related to child development, to deaths associated with iodine-deficiency and to adverse effects are needed.

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