Mandatory Versus Voluntary Implementation of Salt Iodization Program for the Last Two Decades in Ethiopia: A Comparative Review of Existing Literatures

Abstract

Background:

Ethiopian government was implementing mandatory salt iodization program for the last decade to eliminate iodine deficiency disorders, but several recent studies reported mixed findings.

Objective:

This review aimed to assess the difference in implementation of iodized salt program 10 years before and after mandatory salt iodization being implemented in Ethiopia since 2011.

Methods:

In Ethiopia, legislation that enforces salt producers to iodize all salts used for human consumption started in February 2011. All studies about iodine deficiency and iodized salt conducted in Ethiopia in the last 2 decades were searched. Searches were performed in PubMed database. Google Scholar, Iodine Global Network, and Ethiopian Public Health Institute websites were also searched.

Results:

A total of 235 titles and abstracts were identified. After scanning the abstracts and full papers, 43 articles were remained for final data synthesis. In this review, all studies conducted before 2011 reported a urinary iodine concentration (UIC) value of < 100 μg/L and 66.7% of them reported a goiter prevalence of > 30%. On the other hand, among studies conducted after 2011, 88.9% reported UIC value < 100 μg/L and 73.7% reported goiter prevalence of > 30%. Household availability of adequately iodized salt increased from nearly 20% in pre 2011 to more than 50% in post 2011 period.

Conclusion:

Despite the efforts made by the Ethiopian government on mandatory salt iodization for the last decade, iodine deficiency is sustained in the country. Moreover, the goal of universal salt iodization program is offtrack and needs urgent revision.

Registration:

Registered on PROSPERO register with reg. no CRD42021251124.

Keywords

Ethiopia iodine deficiency mandatory legislation universal salt iodization

Introduction

Despite global improvement in iodine nutrition status, achieving sustainable elimination of its deficiency remained a great challenge in many African countries including Ethiopia.¹ Beside poor consumption of iodized salt, knowledge gap, misperceptions, and improper practices of iodized salt were major problems in Ethiopia, as indicated by previous studies.^2
-4

Young children and pregnant women are the most vulnerable groups of iodine deficiency (ID).⁵ Iodine deficiency has serious effect in these groups leading to easily preventable cognitive impairment.⁶ Despite its ill-effect, iodine deficiency disorders (IDD) are among the easiest and cheapest of all disorders to prevent. The addition of a small, constant amount of iodine to the salt that people consume every day is all that is needed.⁷

After recognizing the consequences of ID and the availability of prevention method, most countries of the world accepted universal salt iodization (USI) as a safe, cost-effective, and sustainable strategy to ensure sufficient intake of iodine and to achieve the virtual elimination of IDD.⁸ Ethiopia was one of these countries in Africa to accept the USI goal of achieving more than 90% utilization of iodized salt by households.

As far back as 1988, Ethiopia was achieved almost 80% iodized salt coverage,⁹ when most iodized salt came from Eritrea (Red sea). The 1998 to 2000 war between Ethiopia and Eritrean interrupted Ethiopia’s iodized salt supply and the country started importing salt from other countries, such as Djibouti and India, much of which was not iodized. As a result, there was a rapid deterioration in the iodine status of population and the percentage of households consuming adequately iodized salt reduced to below 10%.⁹ This was supported by 2 national surveys conducted in 2005¹⁰ and 2011.¹¹ According to the report of these surveys, only 4.2% and 15.4% of the Ethiopian population use iodized salt respectively. Another national survey conducted in 2016 tested the presence of potassium iodate in household salt using rapid test kit and reported 89.2% coverage of iodized salt. However, in the same survey, a subsample of salt was measured for its iodine content using titration method. According to the finding, only 26% of households get adequate iodized salt for better nutrition.¹²

Currently, Ethiopia is producing its own iodized salt using KIO₃ compound in Afar and Somali regions of the country. In addition, in February 2011, the Council of Ministers passed mandatory legislation requiring salt producers to iodize their salt for human consumption and in 2012; the government of Ethiopia began to enforce the new rules.^9,13 However, whether the program is going on as intended or not is in question, because several recently conducted national and subnational studies reported a mixed finding. Most of the studies reported presence of severe ID and low availability of adequately iodized salt in Ethiopia.^2
-4,14
-16 On the contrary, some recently conducted national and subnational studies revealed that the country is iodine sufficient and the national household iodized salt coverage reached 89.2%.^12,17

The Research Question

The major research question that initiated this systematic review was the following:

“How mandatory salt iodization program implemented for the last 10 years (2011-2020) differ from the previous voluntary implementation period (2001-2010) in reducing IDD and achieving USI goal in Ethiopia?”

To answer the above question, this review assessed the current iodine nutrition status indicator (median urinary iodine concentration [mUIC]), long-term ID impact indicator (goiter prevalence), and iodine content of salt at household level. The indicators were assessed in all papers published in the last 2 decades (2001-2020) in Ethiopia and compared for the differences.

According to World Health Organization (WHO), mUIC is the main indicator used to assess iodine status of a population.¹⁸ Goiter prevalence may be useful in assessing thyroid function and long-term iodine nutrition status. However, a combination of mUIC, goiter prevalence, and availability of adequately iodized salt at household level can be used to assess the impact of salt iodization on the reduction of IDD and sustainability of ID prevention and control programmes.^7,18

Based on the above research question, this review assessed the difference in implementation of previous voluntary and current mandatory salt iodization programs and compared its impact in prevention and control of IDD and utilization of iodized salt.

Methods

Search Strategies

This review was conducted from May 1 to June 30, 2021. During this period, all studies about ID and iodized salt conducted in last 2 decades (2001-2020) in Ethiopia were searched. The period of the study searched was limited to 20 years because mandatory legislation that enforces salt producers to iodize all salts used for human consumption was passed by Ethiopian government in 2011 (10 years back) and it is fair to compare this period with the similar previous nonmandatory salt iodization period (10 years before 2011).

The search terms included were keywords describing the following concepts: “Iodine” and “Ethiopia”; iodized salt and “Ethiopia”; “Universal Salt Iodization” and “Ethiopia”; “Availability of iodized salt at household” and “Ethiopia”; “Iodine deficiency” and “Ethiopia”; “Causes of iodine deficiency” and “Ethiopia”; “Iodine deficiency disorders (IDD)” and “Ethiopia”; “Effects of iodine deficiency” and ‘Ethiopia”; “IDD indicators” and “Ethiopia”; Urinary iodine concentration” and “Ethiopia”; “Urinary iodine excretion” and “Ethiopia”; “Thyroid gland enlargement” and “Ethiopia”; “Goiter” and “Ethiopia”; “knowledge of iodine deficiency” and “Ethiopia”; “knowledge of iodized salt” and “Ethiopia”.

Using the above terms, searches were performed in PubMed database for relevant articles published in English language. Google Scholar and Iodine Global Network (IGN) websites were also searched and Ethiopian Public Health Institute was contacted for possible grey literatures (workshops, reports, newsletters, and conference proceedings).

Eligibility Criteria

Inclusion criteria

An attempt was made to include all study designs in this review, as such inclusive approach allows for examination of the totality of empirical evidence and may provide invaluable insights regarding the agreement or disagreement of the results from different study designs. Therefore, studies that fulfilled the following criteria were included:

All studies about iodine nutrition status and iodized salt in the last 20 years (2001-2020)

Only studies conducted in Ethiopia (primary, review, or grey literature)

Studies that reported any of the following outcomes: goiter prevalence, median UIC, and household salt iodine content.

Exclusion criteria

Studies with the following characteristics were excluded:

Published after February 2011, but the data collected before 2011

Studies conducted in individuals with thyroid disorders

Studies published/written in languages other than English.

Study Selection

Two reviewers independently assessed the title, abstract, and keywords of references for potential relevance. The full manuscript was retrieved when the prespecified inclusion criteria were met or when there was uncertainty to reject the study. An adapted reporting item for systematic reviews (PRISMA) flowchart was used to depict the selection of studies for inclusion and the grey literatures were included based on relevance (Figure 1).

Figure 1.

PRISMA Flow Diagram.

Data Extraction

Data extraction parameters were ID indicators or markers (mUIC, goiter prevalence, and household salt iodine content). Data were extracted and tabulated independently by the 2 reviewers. All of the retrieved publications were checked for agreement between the reviewers. When there was discordance between the 2 reviewers against the set criteria, a third reviewer (senior professor in nutrition) was invited to review the discordant results and his report was taken as a final resolution for the disagreement.

Outcome Measurement

There were 3 main outcomes in this review. Median UIC at population level, adequately iodized salt at household level, and goiter prevalence at population level that indicates long-term impact of iodine insufficiency. In addition to these main indicators, other programmatic indicators assessed by the primary authors were also considered. Such programmatic indicators include government concerns (political will), availability and access of laboratories to measure UIC and salt iodine content, presence of active educational and social mobilization programs on the importance of iodine, and the use of iodized salt and presence of robust monitoring systems.

Quality Assessment of the Included Studies

All papers selected for inclusions in the review were subjected to a rigorous appraisal by 2 independent reviewers using the Joanna Briggs Institute quality appraisal tool adapted for studies reporting prevalence data.¹⁹ Then the 2 reviewers work was cross-referenced and any disagreements were discussed with a third independent reviewer for final resolution.

Items used to appraise the included studies were (1) inclusion criteria, (2) study subject and setting, (3) valid and reliable exposure measurement, (4) use of objective and standard criteria, (5) confounder factors identification, (6) strategies for confounder identification, (7) valid and reliable outcome measurement, and (8) use of appropriate statistical analysis.

Studies were considered low quality and excluded from the review whenever the cumulative fitted result is below 50% in the quality assessment checklist criteria.¹⁹ Accordingly, no study was excluded in our review Table 1.

Table 1.

Critical Appraisal Result of the Included Studies, 2021.

Authors of included articles	Year of publication	Criterion number (Items included to appraise included studies)^a
Authors of included articles	Year of publication	1	2	3	4	5	6	7	8	%
Takele et al²⁰	2003	X	✓	✓	✓	✓	✓	X	✓	75.0
Berhanu et al²¹	2004	✓	✓	X	✓	✓	✓	X	✓	75.0
CSA, EDHS¹¹	2005	✓	✓	X	✓	X	X	✓	✓	62.5
Kidane & Woldegebriel²²	2006	✓	X	✓	✓	✓	✓	✓	✓	87.5
Abuye et al¹⁰	2007	✓	✓	✓	✓	✓	✓	X	✓	87.5
Abuye & Berhane²³	2007	✓	✓	✓	✓	✓	✓	X	✓	87.5
Bezabih et al²⁴	2007	✓	✓	✓	✓	✓	✓	X	✓	87.5
Abuye et al²⁵	2008	✓	✓	✓	✓	✓	✓	✓	✓	100.0
Bogale et al²⁶	2009	✓	✓	✓	✓	✓	✓	X	✓	87.5
CSA, EDHS¹¹	2012	✓	✓	X	✓	X	✓	X	✓	62.5
Gebremariam et al²⁷	2013	✓	✓	✓	✓	✓	✓	X	✓	87.5
Gebriel et al²⁸	2014	✓	✓	✓	✓	✓	✓	X	✓	87.5
Girma et al²	2014	✓	✓	✓	✓	✓	✓	✓	✓	100.0
Kedir et al²⁹	2014	✓	✓	✓	✓	✓	✓	X	✓	87.5
Mesele et al³⁰	2014	✓	✓	✓	✓	✓	✓	✓	✓	100.0
Wolka et al³¹	2014	✓	✓	✓	✓	X	X	X	✓	62.5
Giday et al³²	2015	✓	✓	✓	✓	✓	✓	X	X	75.0
Hailu et al⁴	2016	✓	✓	X	✓	✓	✓	✓	✓	87.5
Trihas et al³³	2016	✓	✓	X	X	✓	✓	X	✓	62.5
Tsegaye et al³⁴	2016	✓	✓	X	✓	✓	✓	X	✓	75.0
Abebe et al³⁵	2017	✓	✓	X	✓	✓	✓	✓	✓	87.5
Anteneh et al³⁶	2017	X	✓	✓	✓	✓	✓	X	✓	75.0
Haji et al³⁷	2017	✓	✓	X	✓	✓	✓	X	✓	75.0
Keno et al³⁸	2017	✓	✓	✓	✓	✓	✓	✓	✓	100.0
Tigabu et al³⁹	2017	✓	✓	X	✓	✓	✓	✓	✓	87.5
Workie et al⁴⁰	2017	✓	✓	X	✓	✓	✓	X	✓	75.0
Bazezew et al⁴¹	2018	✓	✓	✓	✓	✓	✓	X	✓	87.5
Fereja et al⁴²	2018	✓	✓	✓	✓	✓	✓	X	✓	87.5
Kumma et al⁴³	2018	✓	X	✓	✓	✓	✓	X	✓	75.0
Mekonnen et al⁴⁴	2018	✓	✓	X	✓	✓	✓	X	✓	75.0
Wassie et al¹⁴	2018	✓	✓	✓	✓	✓	✓	✓	✓	100.0
Bekele & Adilo⁴⁵	2019	✓	✓	✓	✓	✓	✓	X	✓	87.5
Desta et al¹⁵	2019	✓	✓	✓	✓	X	X	X	✓	62.5
Endalamaw et al⁴⁶	2019	✓	✓	✓	✓	✓	✓	X	✓	87.5
Hassen et al⁴⁷	2019	✓	✓	✓	✓	✓	✓	✓	✓	100.0
Muktar et al¹⁶	2019	✓	✓	✓	✓	✓	✓	X	✓	87.5
Tariku & Mazengia⁴⁸	2019	✓	✓	✓	✓	✓	✓	X	✓	87.5
Ajema et al⁴⁹	2020	✓	✓	✓	✓	X	X	X	✓	62.5
Asfaw & Belachew⁵⁰	2020	✓	✓	✓	✓	✓	✓	✓	✓	100.0
Gebrmichael et al⁵¹	2020	✓	✓	✓	✓	✓	✓	X	X	75.0
Mesfin et al⁵²	2020	✓	✓	✓	✓	✓	✓	X	✓	87.5
Obssie et al⁵³	2020	✓	✓	X	✓	X	X	X	✓	50.0
Zekarias et al⁵⁴	2020	✓	✓	✓	✓	✓	✓	X	✓	87.5

Abbreviations: √, Criterion fulfilled; X, criterion not fulfilled.

^a Criterion numbers: (1) Inclusion criteria, (2) Study subject and setting, (3) Valid and reliable exposure measurement, (4) Use of objective and standard criteria, (5) Confounder factors identification, (6) Strategies for confounder identification, (7) Valid and reliable outcome measurement, and (8) Use of appropriate statistical analysis.

Data Synthesis

As there were no randomized controlled trial (RCT) or quasi-experimental design in included studies, a meta-analysis was not conducted. In addition, due to the heterogeneity relating to the goiter examination and grading, variation in participants and outcomes assessed, the main data analysis method used was a narrative approach. The synthesis aimed to describe the existing body of literature and identified strengths and gaps in the prevention of ID and utilization of iodized salt in last 2 decades in Ethiopia. The findings were summarized in a narrative interpretation focusing on years of publication, characteristics of study participants, outcome measures, the way outcome variables assessed/measured and the aims of the review.

Results and Discussion

Studies Characteristics

A total of 235 abstracts were identified in our search, of which 107 duplicates were excluded and the remaining articles were scanned for titles and abstracts. A total of 58 articles remained for full-text assessment. During full-text assessment, 15 articles which did not fulfill the set criteria were excluded with reasons and 43 full-text articles were used for final data synthesis. Almost all studies included for full-text assessment were cross-sectional design except one study which was systematic review.

No reports were found on RCTs or quasi-experimental studies concerning iodine nutrition and the consequences of its deficiency in Ethiopia. Because the numbers of research reports in the country were relatively small and of similar design, they were all included in the review. The extracted studies, outcome variables with their measurement, and major findings of published studies were summarized in Table 2.

Table 2.

Design, Outcome Variables With Their Measurement, and Major Findings of Published Studies on IDD and Iodized Salt in Ethiopia in Last 2 Decades (2001-2020).^a

Author (s), year	Study design	Sample size (n)	participants	*mUIC level (measurement)	**Goiter prevalence (assessment method)	***Adequately iodized salt at HH (Assessment method)	Limitations reported or detected
Takele et al, 2003	Cross-sectional (community-based)	n₁ = 33 n₂ = 299	n₁ = shopkeepers, n₂ = food caterers	NM	NA	19.0% (titration)	Goiter and UIC were not assessed
Berhanu et al, 2004	Cross-sectional (school-based)	1044	Children 6-12 years	NM	27.4% (palpation)	NA	UIC not assessed
CSA, EDHS 2005*	Cross-sectional (community-based)	20 103	All population groups	NM	NA	20% (RTK)	Titration test not done
Kidane et al, 2006	Cross-sectional (community-based)	946	Not specified	NM	Adjusted = 57.2% (palpation)	NA	Recent iodine status not assessed
Abuye & Berhane, 2007	Cross-sectional (community-based)	10 998	Women of reproductive age group (15-49 years)	NM	35.8% (palpation & inspection)	10% (RTK)	UIC not assessed
Abuye et al, 2007	Cross-sectional (community-based)	10 965	Children (6-12 years)	20.45 μg/L (wet digestion method)	39.9% (palpation & inspection)	4.2% (RTK)	None
Bezabih et al, 2007	Cross-sectional (school)	386	Children 6-12 years	58.8 μg/L (wet digestion method)	NA	NA	Long term ID not assessed
Abuye et al, 2008	Cross-sectional (epidemiological study)	n₁ = n₂ = 6960	Children (n₁) & their biological mothers (n₂)	Ranges from 30.8-70.5 μg/L (wet digestion)	>20% in both n₁ and n₂ (palpation)	Ranges from 1.5% to 19.5% in different regions (RTK)	None
Bogale et al, 2009	Cross-sectional (community-based)	n₁ = n₂ = 100	n₁ = women, n₂ = 5 year children	1 μg/L in all cases (wet digestion)	85.0% in n₁ and 33.0% in n₂ (palpation)	Adequately iodized salt use = 2% (RTK)	Full-text not accessed
Gebremariam et al, 2013	Cross-sectional (community-based)	814	HH members responsible for meal preparation	NM	NA	28.9% (RTK)	Both UIC and goiter prevalence were not assessed
Gebriel et al, 2014	Cross-sectional (community-based)	395	Children (6-12 years)	NM	26.3% (palpation)	26.1% (RTK)	UIC not assessed
Girma et al, 2014	Cross-sectional (school based)	200	School children (6-18 years)	39.9 μg/L (Spectrophotometry)	39.5% (palpation)	10.0% (RTK)	Unjustified small sample (Low power)
Kedir et al, 2014	Cross-sectional (community-based)	525	Pregnant women	58.1 μg/L (wet digestion)	NA	13.0% (RTK)	Long-term ID not assessed
Mesele et al, 2014	Cross-sectional (community-based)	698	School children (6-12 years)	NM	37.6% (palpation)	29.7% (RTK)	Observer bias in goiter grading
Wolka et al, 2014	Cross-sectional (community-based)	270	School children (6-12 years)	NM	54.8% in girls and 45.2% in boys (palpation)	NA	Risk of confounding
Giday et al, 2015	Cross-sectional (community-based)	610	Any adult households members	NM	NA	33.0% (RTK)	Both UIC and goiter prevalence were not assessed
Hailu et al, 2016	Cross-sectional (school)	422	Children (6-12 years)	78.0 μg/L (ammonium ps. test)	43.5% (palpation)	29.0% (RTK)	Lack external validity
Trihas et al, 2016	Systematic review	24 papers	Women and children	Not applicable	35.8% (pooled)	Reached up to ∼88%, but not sustained (pooled)	All primary studies were observational
Tsegaye et al, 2016	Cross-sectional (comparative)	909 (303 U vs. 606 R)	Selected urban (U) and rural (R) dwellers	NM	NA	73.3% (WYD iodine checker)	Both UIC and goiter prevalence were not assessed
CSA, EDHS 2016*	Cross-sectional (community-based)	28 371	All eligible population	NM	NA	89% (RTK)	Titration test not used
Abebe et al, 2017	Cross-sectional (school)	757	Children (6-12 years)	NM	29.1% (palpation)	32.5% (RTK)	UIC not assessed Social desirability bias
Anteneh et al, 2017	Cross-sectional (community-based)	1194	Households	NM	NA	57.4% (titration)	Both UIC and goiter prevalence not assessed
Haji et al, 2017	Cross-sectional (community-based)	556	HH members responsible for meal preparation	NM	NA	46.4% (RTK)	Both UIC and goiter prevalence not assessed
Keno et al, 2017	Cross-sectional (school & community based)	n₁ = 73 n₂ = 40	children 6-12 years (n₁) and pregnant women (n₂)	70.5 μg/L (n₁), 88.6 μg/L (n₂) (ammonium ps. test)	NA	33.0% (titration)	Small sample size (low power)
Tigabu et al, 2017	Cross-sectional (school)	454	Children (7-12 years)	NM	62.1% (palpation)	61.2% (RTK)	Lack of external validity
Workie et al, 2017	Cross-sectional (school)	740	School adolescents	NM	48.9% (palpation)	NA	UIC not measured
Bazezew et al, 2018	Cross-sectional (community-based)	550	Women of reproductive age group	NM	NA	76.3% (RTK)	Titration test not done
Fereja et al, 2018	Cross-sectional (community-based)	356	Pregnant women	85.7 μg/L (ICP-MS)	20.2% (palpation)	39.3% (WYD iodine checker)	None
Kumma et al, 2018	Cross-sectional (community-based)	441	Adult HH members	NM	NA	37.7% (titration)	Both UIC and goiter prevalence not assessed
Mekonnen et al, 2018	Cross-sectional (community-based)	753	Any adult household member	NM	NA	68.8% (RTK)	Lack external validity, UIC, goiter not assessed
Wassie et al, 2018	Cross-sectional (school)	349	Children (6-12 years)	235.0 μg/L (Sandell Kolthoff reaction)	43.5% (palpation & inspection)	30.7% (RTK)	Intra-assessor variation in goiter grade
Bekele & Adilo, 2019	Cross-sectional (school)	422	Children (6-12 years)	NM	36.6% (palpation)	NA	UIC & salt not assessed
Desta et al, 2019	Cross-sectional (community-based)	318	HH food handlers (women)	NM	NA	17.5% (RTK)	Lack of external validity (one region only)
Endalamaw et al, 2019	Cross-sectional (institution-based)	404	Pregnant women	NM	39.4% (palpation)	59.9% (RTK)	Recent iodine status not assessed
Hassen et al, 2019	Cross-sectional (school)	767	Children (6-12 years)	74.0 μg/L (spectrophotometry)	16.0% (palpation)	50.8% (Interview)	Social desirability bias
Muktar et al, 2019	Cross-sectional (school)	418	Children (6-12 years)	NM	51.8% (palpation)	8.4% (RTK)	Lack of external validity
Tariku & Mazengia, 2019	Cross-sectional (community-based)	714	Head of HH	NM	NA	63.3% (RTK)	Titration not done
Ajema et al, 2020	Cross-sectional (community-based)	875	Food handler in the HH (>18 years)	NM	NA	58.2% (titration)	Social desirability bias
Asfaw & Belachew, 2020	Cross-sectional (both community- & school-based)	652	School-age children (6-12 years)	96.12 μg/L (Sandell Kolthoff reaction)	54.6% (palpation)	19.1% (RTK)	Titration test not done
Gebrmichael et al, 2020	Cross-sectional (community-based)	596	Adolescents (10-19 years)	NM	42.5% (palpation)	70.5% (RTK)	Recall bias (dietary habit)
Mesfin et al, 2020	Cross-sectional (institution-based)	620	Adolescent high school girls	NM	24.1% (palpation)	73.8% (RTK)	UIC not measured
Obssie et al, 2020	Cross-sectional (community-based)	394	Any HH member (>18 years)	NM	NA	56.6% (RTK)	No titration UIC & goiter not assessed
Zekarias et al, 2020	Cross-sectional (community based)	584	Women of reproductive age group	NM	43.3% (palpation)	28.4% (interview)	UIC not measured, Recall bias

Abbreviations: HH, household; IDD, iodine deficiency disorders; NA, not assessed; NM, not measured; RTK, rapid test kit (qualitative method); UIC, urinary iodine concentration; ICP-MS, inductively coupled plasma-mass spectrometry; ps. test, per sulfate test.

^a According to WHO⁷: *mUIC = the cutoff for normal median UIC is 100 μg/L; **Goiter prevalence is considered as a public health problem if it is ≥5% and endemic if it exceeds 10%; and ***Adequately iodized salt = salt is said to be adequately iodized, when a sample of salt tested using rapid test kit gives a deep blue color.

Prevalence of Iodine Deficiency Disorders in Ethiopia (2001-2020)

According to WHO/UNICEF/IGN, the mUIC taken from a representative sample is a good indicator of the current iodine status in the general population and any mUIC value < 100 μg/L is considered as an indicator of ID at population level.¹⁸ Previously, the prevalence of goiter was considered as a public health problem if it is equal to or greater than 5% and endemic if it exceeds 10%⁷ but currently, the prevalence of goiter is no more used as a sensitive indicator of ID. It may be used to assess a long-term impact of iodine insufficiency in a given population.

Median urinary iodine concentration

In this review, among the 9 studies conducted before 2011, 4 of them (44.4%) assessed mUIC and all of them reported a mUIC value of < 100 μg/L (100.0%). Among the 4 studies, 2 of them (50.0%) conducted in school children aged 6 to 12 years and the remaining 2 (50.0%) conducted in both the children and their biological mothers. Similarly, among 34 studies conducted after 2011, 9 of them (26.5%) assessed mUIC and 8 of the studies (88.9%) reported a mUIC value of < 100 μg/L. Six out of the 9 (66.7%) studies were conducted in school-age children and the remaining 3 (33.3%) were conducted in pregnant women. Due to such variation in participants and number of studies that assessed mUIC, it is hard to conclude that the observed difference is the mere result of mandatory program implementation. However, the mUIC at population level was < 100 μg/L in all primary studies included in this review. This fact indicates that, despite the efforts made by the Ethiopian government on mandatory salt iodization for the last decade, ID is sustained in the country.

Goiter prevalence

World Health Organization categorizes the prevalence of goiter as mild, moderate, and severe if its prevalence is 5% to 19.9%, 20% to 29.9%, and greater or equal to 30% respectively. Among the 9 studies conducted before 2011, 6 of them (66.7%) assessed goiter prevalence and 4 of them (66.7%) reported a goiter prevalence of more than 30% and the remaining 2 studies reported the prevalence of 20% and 27.4%. On the other hand, among 34 studies conducted after 2011, 19 (55.9%) of them assessed goiter prevalence and 14 (73.7%) of them reported a goiter prevalence of more than 30%. In the other 5, the prevalence ranged from 16% to 29.1%.

In this review, all studies reported more than 10% prevalence of goiter confirming that it is an endemic in the country.⁷ However, we cannot determine iodine status of population using goiter prevalence, as changes in goiter prevalence lag behind changes in iodine status. Therefore, it is no more used as a sensitive indicator of iodine nutrition status and cannot be relied upon to accurately reflect current iodine intake. However, it can be used to assess program sustainability and progress when used in combination with mUIC levels in the population, availability of adequately iodized salt at the household level, and other programmatic indicators.

Iodine Content of Household Salt in the Last 2 Decades in Ethiopia

World Health Organization recommends a daily intake of 90 µg of iodine for preschool children (0-59 months); 120 µg for schoolchildren (6-12 years); 150 µg for adolescents (above 12 years) and adults; 250 µg for pregnant and lactating women.⁴ To achieve these requirements, many countries of the world are implementing the goal of USI (more than 90% of households using iodized salt).

Ethiopia as a country accepted the strategy and passed a mandatory legislation requiring salt producers to iodize their salt for human consumption. In addition, following the border conflict between Ethiopia and Eritrea (1998-2000), the country began to explore indigenous salt production sources in different sites and started producing about 95% of the salt for its own use in the country. Despite these and other efforts made by the Ethiopian government, several recent researches had shown conflicting results about the Ethiopia’s progress toward achieving the goal of USI.^3,11,51,53

In a study conducted in eastern Ethiopia, the median UIC was 146 μg/L reflecting iodine sufficiency at population level, but 31% of the study participants had UIC < 100 μg/L (though an individual’s UIC value cannot be used to judge iodine status of any population) and utilization of inadequately iodized salt were high (90.0%).³ Another study conducted in northeast Ethiopia had shown high prevalence of goiter (42.5%).⁵¹ Similarly, the southeast Ethiopian study revealed only 56.6% of households were using adequately iodized salt⁵³ which is far below WHO recommendation (> 90%).

According to this review, in all studies conducted before 2011, the availability of adequately iodized salt at household level was found to be less than or equal to 20%. However, in studies conducted after 2011, only 14.3% reported less than 20% availability. Nearly half of the studies (46.4%) reported more than 50% possession of adequately iodized salt at household level. This finding indicates that the availability of adequately iodized salt at household level increased from nearly 20% to more than 50%. However, we cannot conclude that the iodized salt utilization is improved after 2011, because of methodological differences. For example, among all studies conducted before 2011, only one study used titration test to assess iodine content of salt at household level, whereas 7 studies used the same method in post 2011 studies. In addition, neither pre nor post 2011 studies had shown the achievement of USI goal of utilizing adequately iodized salt by more than 90% of the households.

Other Programmatic Indicators

In addition to the main iodine status indicators, it is important to assess other programmatic indicators which are regarded as evidence of sustainability. Among 43 primary studies included in this review, 4 of them (9.3%) reported less political commitment from government side, 5 (11.6%) complained poor access to UIC and salt testing laboratories, and 7 (16.3%) reported absence of effective monitoring system to assess the iodine status of population. Above all, majority of the studies, 28 (65.0%) raised the need for social mobilization and awareness creation programs on the importance of iodine and the use of iodized salt.

Limitations of the Review

Except one, all the primary studies included in this review used cross-sectional deign. Even though WHO recommends such design with a representative sample for population level iodine status studies, they often had methodological weakness.

For determination of iodine content of household salt sample, most primary studies used iodine rapid test kit which shows only the presence or absence of iodine in the salt.

Most of the primary studies included in this review were area specific and subnational which may not represent the national figure. However, we tried to include different studies from all regions in addition to the 5 national surveys conducted in the country.

Conclusion

This review used all relevant studies published in last 2 decades and provided them in a single document for policy makers to reach evidence-based decision-making. The review is the most recent compilation of studies regarding the difference in implementing voluntary and mandatory salt iodization programs. It compared the 2 period implementation statuses. The findings suggested that ID is sustained in the country, despite the efforts made by the Ethiopian government on mandatory salt iodization for the last decade. In addition, the USI program aimed to achieve the goal of utilizing adequately iodized salt by more than 90% of the households is offtrack and calls for a revision of its implementation strategies.

Recommendations

There is urgent need for revision of USI program strategies, action plans, and the legislation as it is offtrack.

National representative survey that encompasses all possible factors that affected the progress of iodized salt program such as loss of iodine at different supply chain management system, poor practice of iodized salt at population level, political will and support from government side, and the monitoring system should be conducted.

Footnotes

Authors’ Note

All methodologies and search strategies were indicated in the manuscript and if additional information is required, corresponding author is ready to share.

Acknowledgment

The authors would like to thank EPHI for the provision of valuable data.

Author Contributions

AA = Conceived and designed the study, performed the search, data extraction, data synthesis, interpretation, and drafted the manuscript. DT = Participated in the study design, search, and data synthesis, and manuscript revision. TB = Participated in the data synthesis, interpretation, and manuscript revision. All authors read and approved the final manuscript.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

ORCID iD

Agize Asfaw

References

Jooste

Andersson

Assey

. Iodine nutrition in Africa: an update. Sight Life. 2013;27(3):50–55.

Girma

Loha

Bogale

Teyikie

Abuye

Stoecker

. Iodine deficiency in primary school children and knowledge of iodine deficiency and iodized salt among caretakers in Hawassa town: southern Ethiopia. Ethiop J Health Dev. 2012;26(1):30–35.

Asfaw

Gari

Belachew

. Effect of nutrition education on iodine deficiency disorders and iodized salt intake in south west Ethiopian women: a cluster randomized controlled trial. BMC Womens Health. 2020;20(1):55. doi:10.1186/s12905-020-01126-y

Aweke

Adamu

Girmay

Yohannes

Alemnesh

Abuye

. Iodine deficiency disorders (IDD) in Burie and Womberma districts, West Gojjam, Ethiopia. AJFAND. 2014;14(4):9170–9178.

Rodriguez-Diaz

Pearce

. Iodine status and supplementation before, during, and after pregnancy. Best Pract Res Clin Endocrinol Metab. 2020;34(4):101430. https://www.sciencedirect.com/science/article/pii/S1521690X20300579

World Health Organization. Iodine Status Worldwide: WHO Global Database on ID. World Health Organization; 2004. Updated June 16, 2021. Accessed February 16, 2021. www.whqlibdoc.who.int/publications/2004/9241592001.pdf

World Health Organization. Assessment of Iodine Deficiency Disorders and Monitoring Their Elimination: A guide for Program Managers. 3rd ed. World Health Organization; 2007. Accessed June 15, 2021. https://apps.who.int/iris/bitstream/handle/10665/43781/978924_eng.pdf?sequence=1

World Health Organization. Indicators for Assessing Iodine Deficiency Disorders and Their Control through Salt Iodization. World Health Organization; 1994 (WHO/NUT/94.6).

Adish

Chuko

Abay

, et al. Ethiopia: Breaking through with a new iodized salt law. IDD Newsletter. Published November 2013.

10.

Abuye

Berhane

Akalu

Getahun

Ersumo

. Prevalence of goiter in children 6 to 12 years of age in Ethiopia. Food Nutr Bull. 2007;28(4):391–398. doi:10.1177/156482650702800403. PMID: 18274165.

11.

Central Statistical Agency [Ethiopia] and ORC Macro EDHS 2005. CSA, Addis Ababa, Ethiopia and Calverton, Maryland, USA. Published 2012. Updated June 30, 2021. Accessed May 25, 2021. https://dhsprogram.com/pubs/pdf/FR179/FR179%5B23June2011%5D.pdf

12.

EPHI. Ethiopian National Micronutrient Survey Report. Published September 2016. Updated June 25, 2021. Accessed February 03, 2021. https://www.ephi.gov.et/images/pictures/download2009/National_MNS_report.pdf

13.

Ambaye

. Knowledge of iodine deficiency disorders and intake of iodized salt in residents of Mekelle Tigray, Ethiopia. J Food Sci Nutr Ther. 2015;1(1):002–007.

14.

Hailu

Wubshet

Woldie

Tariku

. Iodine deficiency and associated factors among school children: a cross-sectional study in Ethiopia. Arch Public Health. 2016;74(46):1–13.

15.

Girma

Nibret

Gedefaw

. The status of iodine nutrition and iodine deficiency disorders among school children in Metekel Zone, Northwest Ethiopia. Ethiop J Health Sci. 2014;24(2):109–116.

16.

Desta

Kulkarni

Abraha

Worku

Sahle

. Iodine level concentration, coverage of adequately iodized salt consumption and factors affecting proper iodized salt utilization among households in North Ethiopia: a community based cross sectional study. BMC Nutr. 2019;18(5):28. doi:10.1186/s40795-019-0291-x. PMID: 32153941; PMCID: PMC7050811.

17.

Wassie

Abebe

Tariku

, et al. Iodine status five years after the mandatory salt iodization legislation indicates above requirement: a cross sectional study in Northwest Ethiopia. BMC Nutr. 2018;20(4):52. doi:10.1186/s40795-018-0261-8. PMID: 32153913; PMCID: PMC7050929

18.

World Health Organization. Urinary Iodine Concentrations for Determining Iodine Status in Populations. Vitamin and Mineral Nutrition Information System. World Health Organization; 2013. Updated June 14, 2021. Accessed February 23, 2021. http://www.who.int/nutrition/vmnis/indicators/urinaryiodine

19.

Downes

Brennan

Williams

Dean

. Development of a critical appraisal tool to assess the quality of cross-sectional studies (AXIS). BMJ Open. 2016;6:e011458. doi:10.1136/bmjopen-2016-011458

20.

Takele

Belachew

Bekele

. Iodine concentration in salt at household and retail shop levels in Shebe town, South West Ethiopia. East Afr Med J. 2003;80(10):532–539. doi:10.4314/eamj.v80i10.8757. PMID: 15250627

21.

Berhanu

WoldeMichael

Bezabih

. Endemic goiter in school children in Southwestern Ethiopia. Ethiop J Health Dev. 2004;18(3):175–178.

22.

Kidane

Woldegebriel

. Prevalence of iodine deficiency disorder in a highland district in Tigray: brief communication. Ethiop J Health Dev. 2006;20(1):59–60.

23.

Abuye

Berhane

. The goitre rate, its association with reproductive failure, and the knowledge of iodine deficiency disorders (IDD) among women in Ethiopia: cross-section community based study. BMC Public Health. 2007;8(7):316. doi:10.1186/1471-2458-7-316. PMID: 17996043; PMCID: PMC2194698

24.

Bezabih

Assefa

Yismaw

Mulu

. Determination of urinary iodine excretion to assess iodine deficiency level and iodine intake in primary school children, Bahir Dar, northwest Ethiopia. Ethiop Med J. 2007;45(4):377–382. PMID: 18326348.

25.

Abuye

Berhane

Ersumo

. The role of changing diet and altitude on goitre prevalence in five regional states in Ethiopia. East Afr J Public Health. 2008;5(3):163–168. doi:10.4314/eajph.v5i3.38997. PMID: 19374318

26.

Bogale

Abebe

Stoecker

Abuye

Ketema

Hambidge

. Iodine status and cognitive function of women and their five year-old children in rural Sidama, southern Ethiopia. East Afr J Public Health. 2009;6(3):296–299. PMID: 20803922.

27.

Gebremariam

Yesuf

Koye

. Availability of adequately iodized salt at household level and associated factors in Gondar town, Northwest Ethiopia. Int Sch Res Notices. 2013;2013:1–6.

28.

Gebriel

Assegid

Assefa

. Cross-sectional survey of goiter prevalence and household salt iodization levels in Assosa Town, Beni Shangul-Gumuz region, west Ethiopia. J Preg Child Health. 2014;1(119):2.

29.

Kedir

Berhane

Worku

. Subclinical iodine deficiency among pregnant women in Haramaya district, eastern Ethiopia: a community-based study. J Nutr Metab. 2014;2014:878926. doi:10.1155/2014/878926. PMID: 25132987; PMCID: PMC4124753

30.

Mesele

Degu

Gebrehiwot

. Prevalence and associated factors of goiter among rural children aged 6-12 years old in Northwest Ethiopia, cross-sectional study. BMC Public Health. 2014;14(7):130. doi:10.1186/1471-2458-14-130. PMID: 24502377; PMCID: PMC3996147

31.

Wolka

Shiferaw

Biadgilign

. The effect of iodine-deficiency disorders on academic achievement of schoolchildren in Southern Ethiopia. Public Health Nutr. 2014;17(5):1120–1124. doi:10.1017/S1368980013000931. PMID: 23591441

32.

Gidey

Alemu

Atnafu

, et al. Availability of adequate iodized salt at household level and associated factors in rural communities of Laelay Maychew District, Northern Ethiopia: a cross sectional study. J Nutr Health Sci. 2015;1(4):403. doi:10.15744/2393-9060.1.403

33.

Gebretsadikan

Troen

. Progress and challenges in eliminating iodine deficiency in Ethiopia: a systematic review. BMC Nutr. 2016;2(12):1–12.

34.

Tsegaye

Hailu

Zegeye

. Availability and utilization of adequately iodized salt by urban and rural households and associated factors in southern Ethiopia, Sidama zone, Bensa Woreda: a comparative cross-sectional study. Int J Food Sci Nutr Eng. 2016;6(3):62–71.

35.

Abebe

Tariku

Gebeye

. Availability of adequately iodized in Northwest Ethiopia: a cross-sectional study. Arch Public Health. 2017;31(75):33. doi:10.1186/s13690-017-0201-0. PMID: 28781775; PMCID: PMC5535292

36.

Anteneh

Engidayehu

Abeje

. Iodine content of dietary salt at household level and associated factors using iodometric titration methods in Dera District, Northwest Ethiopia. BMC Nutr. 2017;28(3):83. doi:10.1186/s40795-017-0203-x. PMID: 32153859; PMCID: PMC7050691.

37.

Haji

Abdurahmen

Paulos

. Knowledge and perception of consumption of iodized salt among food handlers in southern Ethiopia. Food Nutr Bull. 2017;38(1):92–102. doi:10.1177/0379572116684909. PMID: 28027670

38.

Keno

Ahrens

Lauvaj

Kurabachew

Biesalski

Scherbaum

. Iodine status in pregnant women and school children of the Aira district in Ethiopia. NFS J. 2017;7:1–7.

39.

Tigabu

Bekele

Dachew

. Prevalence of goiter and associated factors among schoolchildren in northeast Ethiopia. Epidemiol Health. 2017:39:e2017055. doi:10.4178/epih.e2017055. PMID: 29172409; PMCID: PMC5790981

40.

Workie

Abebe

Gelaye

Mekonen

. Assessing the status of iodine deficiency disorder (IDD) and associated factors in Wolaita and Dawro Zones School Adolescents, southern Ethiopia. BMC Res Notes. 2017;10(1):156. doi:10.1186/s13104-017-2480-5. PMID: 28420409; PMCID: PMC5395884

41.

Bazezew

Yallew

Belew

. Knowledge and practice of iodized salt utilization among reproductive women in Addis Ababa City. BMC Res Notes. 2018;11(1):734. doi:10.1186/s13104-018-3847-y. PMID: 30326961; PMCID: PMC6192364

42.

Fereja

Gebremedhin

Gebreegziabher

Girma

Stoecker

. Prevalence of iodine deficiency and associated factors among pregnant women in Ada district, Oromia region, Ethiopia: a cross-sectional study. BMC Pregnancy Childbirth. 2018;18(1):257. doi:10.1186/s12884-018-1905-z. PMID: 29940879; PMCID: PMC6019206

43.

Kumma

Haji

Abdurahmen

Mehretie Adinew

. Factors affecting the presence of adequately iodized salt at home in Wolaita, Southern Ethiopia: community based study. Int J Food Sci. 2018;2018:4394908. doi:10.1155/2018/4394908. PMID: 29765978; PMCID: PMC5885487.

44.

Mekonnen

Eshete

Wasihun

Arefaynie

Cherie

. Availability of adequately iodized salt at household level in Dessie and Combolcha Towns, South Wollo, Ethiopia. BMC Public Health. 2018;18(1):1152. doi:10.1186/s12889-018-6066-5. PMID: 30285772; PMCID: PMC6168997

45.

Bekele

Adilo

. Prevalence of goiter and its associated factors among primary school children in Chole District, Arsi Zone, Ethiopia: a cross-sectional study. BMC Nutr. 2019;5(1):5. doi:10.1186/s40795-018-0267-2. PMID: 32153919; PMCID: PMC7050880

46.

Endalamaw

Kedir

Alemayehu

. Visible goiter among pregnant women attending antenatal clinic in public health facilities of Debre Markos Town, East Gojjam, North West Ethiopia. J Nutr Metab. 2019;2019:2484523. doi:10.1155/2019/2484523. PMID: 31929902; PMCID: PMC6942858.

47.

Hassen

Beyene

Ali

. Dietary pattern and its association with iodine deficiency among school children in southwest Ethiopia; a cross-sectional study. PLoS One. 2019;14(8):e0221106. doi:10.1371/journal.pone.0221106. PMID: 31408495; PMCID: PMC6692009

48.

Tariku

Mazengia

. Knowledge and utilization of iodized salt and its associated factors at household Level in Mecha district, Northwest Ethiopia. J Nutr Metab. 2019;2019:9763830. doi:10.1155/2019/9763830. PMID: 31032115; PMCID: PMC6458897.

49.

Ajema

Bekele

Yihune

Tadesse

Gebremichael

Mengesha

. Socio-demographic correlates of availability of adequate iodine in household salt: a community-based cross-sectional study. BMC Res Notes. 2020;13(1):125. doi:10.1186/s13104-020-04983-w. PMID: 32131883; PMCID: PMC7057523

50.

Asfaw

Belachew

. Magnitude of iodine deficiency disorder and associated factors in Dawro zone, Southwest Ethiopia; the hidden hunger: a cross-sectional study. BMC Nutr. 2020;8(6):20. doi:10.1186/s40795-020-00345-8. PMID: 32523711; PMCID: PMC7278065

51.

Gebremichael

Demena

Egata

Gebremichael

. Prevalence of goiter and associated factors among adolescents in Gazgibla District, Northeast Ethiopia. Glob Adv Health Med. 2020;9:2164956120923624. doi:10.1177/2164956120923624. PMID: 32435526; PMCID: PMC7223861

52.

Mesfin

Misganaw

Hunegnaw

Muhammad

. Goiter and its associated factors among adolescent high school girls at tach Armachiho District, Northwest Ethiopia: an institution-based cross-sectional study. J Nutr Metab. 2020;2020(23):3695952. doi:10.1155/2020/3695952. PMID: 33149948; PMCID: PMC7603612

53.

Obssie

Ketema

Tekalegn

. Availability of adequately iodized dietary salt and associated factors in a town of southeast Ethiopia: a community-based cross-sectional survey. J Nutr Metab. 2020;4:1357192. doi:10.1155/2020/1357192. PMID: 33489359; PMCID: PMC7803098

54.

Zekarias

Mesfin

Mengiste

Tesfaye

Getacher

. Prevalence of goiter and associated factors among women of reproductive age group in Demba Gofa Woreda, Gamo Gofa Zone, Southwest Ethiopia: a community-based cross-sectional study. J Nutr Metab. 2020;2020:5102329. doi:10.1155/2020/5102329. PMID: 33489363; PMCID: PMC7803130

55.

Abebe

Gebeye

Tariku

. Poor dietary diversity, wealth status and use of un-iodized salt are associated with goiter among school children: a cross-sectional study in Ethiopia. BMC Public Health. 2017;17(1):44. doi:10.1186/s12889-016-3914-z. PMID: 28061776; PMCID: PMC5219792

56.

Bougma

Aboud

Lemma

Frongillo

Marquis

. Introduction of iodised salt benefits infants’ mental development in a community-based cluster-randomised effectiveness trial in Ethiopia. Br J Nutr. 2018;119(7):801–809. doi:10.1017/S0007114517003658. PMID: 29569536.

57.

Chuko

Bagriansky

Brown

. Ethiopia’s long road to USI. IDD Newsletter. Published May 2015. Updated June 17, 2021. Accessed February 03, 2021. https://www.ign.org/newsletter/idd_may15_ethiopia.pdf

58.

Shawel

Hagos

Lachat

Kimanya

Kolsteren

. Post-production losses in iodine concentration of salt hamper the control of iodine deficiency disorders: a case study in northern Ethiopia. J Health Popul Nutr. 2010;28(3):238–244.

59.

Ersino

Tadele

Bogale

Abuye

Stoecker

. Clinical assessment of goiter and low urinary iodine concentration depict presence of severe iodine deficiency in pregnant Ethiopian women: a cross-sectional study in rural Sidama, southern Ethiopia. Ethiop Med J. 2013;51(2):133–141. PMID: 24079157.

60.

Gebreegziabher

Woltamo

Thomas

Kennedy

Stoecker

. Iodine supplementation of lactating women and assessment of infant visual information processing and maternal and infant thyroid function: a randomized trial. PLoS One. 2019;14(10):e0223348. doi:10.1371/journal.pone.0223348. PMID: 31589645; PMCID: PMC677924.

61.

Hailu

. Remarkable progress against iodine deficiency in Ethiopia. IDD Newsletter. Updated June 17, 2021. Published August 2017. Accessed February 03, 2021. https://www.ign.org/cm_data/idd_aug17_1.pdf

62.

Mezgebu

Mossie

Rajesh

Beyene

. Prevalence and severity of iodine deficiency disorder among children 6-12 years of age in Shebe Senbo district, Jimma zone, southwest Ethiopia. Ethiop J Health Sci. 2012;22(3):196–204. PMID: 23209354; PMCID: PMC3511898.

63.

Mohammed

Marquis

Aboud

Bougma

Samuel

. Pre-pregnancy iodized salt improved children’s cognitive development in randomized trial in Ethiopia. Matern Child Nutr. 2020;16(3):e12943. doi:10.1111/mcn.12943. PMID: 31912649; PMCID: PMC7296810.

64.

Muktar

Roba

Mengistie

Gebremichael

. Iodine deficiency and its associated factors among primary school children in Anchar district, Eastern Ethiopia. Pediatric Health Med Ther. 2018;4(9):89–95. doi:10.2147/PHMT.S165933. PMID: 30233084; PMCID: PMC6130311.

65.

Tesema

Belay

Zerfu

, et al. Reviews of the prevalence of iodine deficiency among vulnerable population in Ethiopia. Micronutrient Forum Global Conference; June 2-6, 2014; Addis Ababa, Ethiopia. Updated June 17, 2021. Accessed February 03, 2021. https://www.ephi.gov.et/images/mcn/Reviews%20of%20the%20Prevalence%20of%20Iodine%20Deficiency.pdf

66.

Wolka

Shiferaw

Biadgilign

. Epidemiological study of risk factors for goiter among primary schoolchildren in southern Ethiopia. Food Nutr Bull. 2014;35(1):20–27. doi:10.1177/156482651403500103. PMID: 24791575.