|Year : 2016 | Volume
| Issue : 3 | Page : 258-263
Iodine nutrition of school children residing in area of local noniodized salt production
Kenechukwu C Onyekwelu1, Ikechukwu E Ezeagu1, Sylverter O Igbedioh2
1 Department of Medical Biochemistry, College of Medicine, University of Nigeria, Enugu Campus, Nigeria
2 Department of Nutrition, UNICEF, A Field Office Enugu, Nigeria
|Date of Web Publication||21-Dec-2016|
Kenechukwu C Onyekwelu
Department of Medical Biochemistry, College of Medicine, University of Nigeria, Enugu Campus, Enugu
Source of Support: None, Conflict of Interest: None
Background: In 1993, Nigeria enacted a law making it mandatory for all salt both for human and animal consumption to be fortified with iodine in a bid to eliminate iodine deficiency disorders (IDDs). IDD is a silent threat to the growth and development of the child and also to national development. The aim of this study was to assess the status of iodine nutrition in schoolchildren in areas known for the production of local uniodized salt.
Materials and Methods: A cross-sectional study was performed in two Local Government Areas of Ebonyi State, Nigeria. Urinary iodine concentration (UIC) was measured in 400 pupils aged 6–12 years old. In addition, the iodine content of kitchen salt samples of the pupils that donated their urine samples were estimated qualitatively using rapid test kit. Salt samples from markets within the localities were also tested to ascertain the level of iodine.
Results: Median UIC of the schoolchildren was 145 μg/L and 31.19% of the schoolchildren had sufficient/adequate iodine intake (100–199 μg/L). Household salt iodization testing showed that 90.0% of the total household salt samples collected during the survey proved iodized; however, only 63.5% were adequately iodized (≥15 parts per million [ppm]). Market salt samples tested showed that three brands of salt were adequately iodized (≥15 ppm), whereas two brands of salt were not iodized (0 ppm).
Conclusion: Even though the median UIC in the total study population was at the recommended level (100–199 μg/L), indicating optimal iodine nutrition, the proportion of households consuming adequately iodized salt (63.5%) was below the recommended target of >90%.
Keywords: Iodine deficiency, iodine nutrition, salt iodization, urinary iodine
|How to cite this article:|
Onyekwelu KC, Ezeagu IE, Igbedioh SO. Iodine nutrition of school children residing in area of local noniodized salt production. Indian J Health Sci Biomed Res 2016;9:258-63
|How to cite this URL:|
Onyekwelu KC, Ezeagu IE, Igbedioh SO. Iodine nutrition of school children residing in area of local noniodized salt production. Indian J Health Sci Biomed Res [serial online] 2016 [cited 2020 Jul 11];9:258-63. Available from: http://www.ijournalhs.org/text.asp?2016/9/3/258/196332
| Introduction|| |
In 1980, the World Health Organization (WHO) estimated that 20–60% of the world's population was iodine deficient and/or goitrous, with most of the burden in developing countries. Iodine deficiency is the single most common cause of preventable mental retardation and brain damage in the world and has multiple adverse effects on growth and development in animals and humans. These are collectively termed the iodine deficiency disorders (IDDs) and are one of the most important and common human diseases., They result from inadequate thyroid hormone production due to lack of sufficient iodine. IDD causes mental retardation or cretinism with possible physical disability in children, and can also lead to miscarriage or stillbirth. Children with IDD can grow up stunted, mentally retarded, and incapable of fast learning. Children in iodine depleted populations can have an intelligent quotient (IQ) of 10–15 percentage points lower than those of iodine replete populations and the reduction in IQ is irreversible. Problems of IDD could be averted by a low-cost intervention using universal salt iodization (USI).
Salt iodization is currently the most widely used strategy to control and eliminate iodine deficiency. However, to be fully effective in correcting iodine deficiency, salt must not only reach the entire affected population but also it needs to be adequately iodized. USI is a term used to describe the iodization of all salt for human (food industry and household) and livestock consumption.
Urinary iodine excretion is a good marker of the very recent dietary intake of iodine and, therefore, is the index of choice for evaluating the degree of iodine deficiency and of its correction. Nigeria in 2005 achieved sustained 98% household access to adequately iodized salt. However, surveys conducted in Nigeria, like the 2007 Nigeria Multiple Indicator Cluster Survey (NMICS) and the 2008 National Demographic Health Survey, showed a decline from 98% USI achieved in 2005. In 2004, National Agency for Food and Drug Administration and Control (NAFDAC) reported that four States in Nigeria (Ebonyi, Nasarawa, Taraba, and Benue) have relatively higher levels of uniodized salt as a result of the local production of uniodized salts. Sustaining Nigeria's celebrated success in USI Programme is, therefore, under serious challenge since all the salt in the market is not iodized.
The objectives of this present study are to determine the availability of iodized salt in households, access the adequacy of iodization of salt consumed by the population, and determine the urinary iodine status of children in the study population.
necessitated this study which was aimed at determining the household access to iodized salt, status of iodine nutrition of primary school children, and the quality of salts sold at markets in Ebonyi State. This study is crucial as it can contribute positively to health development of children and evaluation of USI Programme in Nigeria.
| Materials and Methods|| |
The research was carried out in Abakaliki and Ohaozara Local Government Areas (LGAs) representing urban and rural communities, respectively. Precision-based approach was used in sample size calculation. Five primary schools were randomly selected from each of the LGA. Forty pupils (boys and girls) aged 6–12 years were randomly selected from each school making a total study subject of 398. Casual morning urine samples were collected from the pupils using plastic bottles screwed with caps. Four hundred kitchen salt samples were collected from the pupils that donated their urine samples using polyethylene pouch for household salt iodization testing. Samples of salt sold in five different markets in Abakaliki and Ohaozara LGAs were also purchased for salt iodization testing.
Determination of urinary iodine concentration
Urinary iodine concentration (UIC) was determined using ICCIDD, UNICEF, and WHO  standard Sandell–Kolthoff colorimetric method which involves the digestion of urine with ammonium persulfate. The urine samples were mixed to suspend sediments. With a micropipette, 250 µl of each urine samples were added into a test tube. The same volume of 250 µl of deionized water was also added into another test tube as blank. A volume of 250 µl of each iodine standards (20, 40, 80, 120, 200, and 300 µg/L) were also pipetted into another test tubes. To each of the set of test tubes (urine samples, water blank, and iodine standards), 1.0 ml of ammonium persulfate was added, mixed gently, and heated for 60 min at 100°C followed by cooling at room temperature. A volume of 2.5 ml of arsenous acid solution was added to all the tubes, vortexed, and allowed to stand for 15 min at room temperature after which 300 µl of ceric ammonium sulfate solution was added and quickly mixed at intervals of about 20–30 s. The test tubes were allowed to stand at room temperature. Exactly 30 min after the ceric ammonium sulfate solution was added to the first test tube, the absorbance was read at 420 nm. The other successive tubes were read at the same interval of 30 min after ceric ammonium sulfate was added. Ensuring the quality of urinary iodine procedure standardization process as established by the Center for Disease Control and Prevention was strictly adhered to during the analysis of urinary iodine.
A standard curve was constructed on graph paper by plotting the iodine concentration of each standard on the abscissa against its optical density at 420 nm on the ordinate. From the curve, the UIC was determined for each sample assayed by finding its absorbance reading on the standard curve and subsequently locating its corresponding iodine concentration.
Household salt iodization testing
The iodine content of the salt samples was qualitatively estimated using the rapid test kits for checking salt iodized with potassium iodide supplied by UNICEF (UNICEF Stock No 05-860-02). These consist of bottles of stabilized starch solution of which one drop is placed on the salt. The intensity of the blue color that develops indicates the approximate iodine level and classified as: – - (none), + - (light blue), and ++ - (deep blue) color changes. In estimating the iodine content of salt, key elements of total laboratory quality assurance for salt iodine were observed.
All data collected were subjected to statistical analysis using the Statistical Package for the Social Sciences (SPSS) version 17 (SPSS Inc. Chicago) to determine the mean, median, frequencies, and relationships. Chi-square was used to test the significance of proportions, with P < 0.05 considered statistically significant.
The approval to undertake this study was sought and obtained from Ebonyi State Primary Education Board and Ebonyi State Ministry of Health. Informed consent was also obtained from the caregivers/parents of the pupils through the head teachers.
| Results|| |
Urinary iodine concentration
The result of UIC analysis in Abakaliki LGA showed that 16 pupils (8.04%) and 32 pupils (16.08%) had moderate and mild iodine deficiency, respectively. While 77 pupils (38.69%) had adequate iodine nutrition, 40 (20.10%) and 33 pupils (16.58%) were at risk of iodine-induced hyperthyroidism and risk of adverse health consequences, respectively [Table 1].
|Table 1: Median urinary iodine of pupils in Abakaliki and Ohaozara Local Government Areas|
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In Ohaozara LGA, the UIC results showed that only one pupil had severe iodine deficiency, 38 pupils (19.09%) had moderate iodine deficiency, 28 (14.07%) had mild iodine deficiency, whereas 70 (35.17%) had adequate iodine nutrition. Forty-five (22.61%) and 17 pupils (8.54%) were at risk of iodine-induced hyperthyroidism and risk of adverse health consequences, respectively [Table 1].
The overall result of urinary iodine analysis of the whole study population (Abakaliki and Ohaozara LGAs) showed that only one pupil (0.25%) had severe iodine deficiency, 54 (13.81%) pupils had moderate iodine deficiency, 60 pupils (15.07%) had mild iodine deficiency, whereas 148 (37.18%) had adequate iodine nutrition. Eighty-five pupils (21.35%) were at risk of iodine-induced hyperthyroidism, and 50 pupils (12.56%) were at risk of adverse health consequences, respectively [Table 1].
Comparing both LGAs showed that higher incidence of insufficient iodine nutrition occurred in Ohaozara (67 pupil) (33.18%) than in Abakaliki (48 pupils) (24.12%); 31.15% (62) of the pupils in Ohaozara fall within the risk level of iodine overnutrition compared to 36.68% (73 pupils) in Abakaliki [Figure 1].
|Figure 1: Compares urinary iodine concentration in Abakaliki and Ohaozara Local Government Areas|
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The UIC for schoolchildren in Abakaliki LGA ranged between 20.0 and 350 µg/L with 160 µg/L as the median value, whereas that of Ohaozara LGA ranged between 15.0 and 380.0 µg/L with 140 µg/L as the median value. The median UIC for the total study population was 145 µg/L [Table 2].
|Table 2: Summary median urinary iodine concentration (μg/L) of pupils in Abakaliki and Ohaozara Local Government Areas|
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Household salt iodization
The result of household salt iodine testing is as shown in [Table 3]. It showed that out of 200 salt samples collected from 200 households in Abakaliki LGA, 4 (2%) had no iodine, 75 (37.5%) had inadequate (<15 parts per million [ppm]) iodine content, and 121 (60.5%) had adequate (>15 ppm) iodine content.
The result of household salt iodine testing in Ohaozara LGA showed that out of 200 salt samples collected from 200 households, 36 (18%) had no iodine, 31 (15.5%) %) had inadequate (<15 ppm) iodine content, and 133 (66.5%) had adequate (>15 ppm) iodine content.
[Table 3] showed that overall result of the total 400 salt samples collected from both LGAs and tested, 40 samples (10%) had no iodine, 106 (26.5%) had inadequate (<15 ppm) iodine content, and 254 (63.5%) had adequate (>15 ppm) iodine content.
While 90.0% of the total household salt samples (400) tested during the survey proved iodized, only 254 (63.5%) appeared to be adequately iodized (>15 ppm). This proportion is below the threshold of 90% recommended by the WHO/UNICEF/ICCIDD and the National Assessment value of 98% attained in 2005 [Figure 2].
[Table 4] shows the results of market salt iodization testing. It showed that out of five salt samples collected from different markets in Abakaliki and Ohaozara LGAs; three seemed to be adequately iodized (>15 ppm) while two were not iodized (0 ppm).
|Table 4: Iodine content of market samples of table salt from Abakaliki and Ohaozara Local Government Areas|
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| Discussion|| |
Urinary iodine concentration
UIC is currently the most practical biochemical marker for iodine nutrition. Assessing urinary iodine status provides information on whether there is adequate iodine intake in the population surveyed. Monitoring the urinary iodine status of a population is helpful in knowing if salt iodization program (or other interventions) is improving iodine intake and if iodine deficiency has been eliminated in the population. Urinary iodine status is the most immediate measure of whether the thyroid gland has adequate iodine to function normally and protect the individual from the manifestations of iodine deficiency.
The median value for the sampled population is the most commonly assessed indicator. The median UIC for the total study population (145 µg/L) indicates adequate iodine intake and is in accordance with the WHO/UNICEF/ICCIDD criteria for elimination of iodine deficiency as a public health problem which requires that the median UIC in the general/total study population should be within the range of 100–199 µg/L. Based on this criteria, the pupils can be said to have had adequate iodine nutrition despite cases of insufficient and excessive iodine intakes. Result of surveys conducted in Nigeria, such as the 1999 Sentinel Site Survey, 2001 National Food Consumption and Nutrition Survey, and 2005 Goiter Prevalence Survey, had median UIC within the sufficient/optimal range of 133.9 µg/L, 150 µg/L, and 131 µg/L, respectively.
Household salt iodization
Monitoring iodine in salt at the household level provides information on what percentage of households' uses salt iodized at any iodine concentration and what percentage uses salt that is within an acceptable range of iodine concentration. This information indicates what is actually used in households on a national basis and provides important information about the successful delivery of iodized salt to the consumer as well as about use of noniodized salt obtained from unconventional marketing sources.
In the total study population [Table 3], 90.0% of the total household salt samples collected during the survey proved iodized, only 63.5% were adequately iodized (>15 ppm). This proportion is below the threshold of above 90% recommended by the WHO/UNICEF/ICCIDD and the national average value of 98% attained in 2005. Salts with no iodine content detected in this study could be locally produced. Ebonyi state is known for the production of local salt as there are many salt lakes located in the state. Schools' surveys in 2002 and 2005 found roughly 1–2% salt with no iodine added at all. Areas of small-scale salt production in Nigeria are Nasarawa, Ebonyi, Taraba, and Benue  and also some parts of Enugu State. In 2004, NAFDAC undertook special activities in these areas of small scale salt production to determine salt production and consumption patterns. Within actual salt producing communities, NAFDAC found 97–100% of families consumed noniodized salt. Some salts were also inadequately iodized. This could be attributed to poor iodization at factory level and iodine losses at the retail level/homes due to packaging. Distributing salt in smaller, airtight, and moisture proof consumer packs of 500 g will significantly improve retention of iodine.
[Figure 2], which is chronicle of USI in Nigeria since 1993 revealed a decline in the National USI achievements of previous years. Based on the NBS/NMICS  report, there was a 23% decline in the National USI between 2005 and 2007. This could be attributed to poor iodization at factory level and iodine losses at the retail level. Similar situation occurred in Ethiopia where iodized salt consumption dropped to as low as 5% as a result of consumption of locally produced uniodized salt. Decline in USI was also reported in Argentina and Indonesia – which were attributed to low-quality iodization.
| Conclusion|| |
The result of this investigation demonstrated that despite normal median urinary iodine, cases of insufficient iodine intake, and excessive iodine intake exist. Some households still consume noniodized salt probably because it is more directly available and cheaper or because of lack of awareness on adverse health consequences associated with consumption of uniodized salt. Therefore, the need for intensive enlightenment campaign by the regulation agencies on the need of consuming adequately iodized salt still exists. The consumption of salt in small packs of 500 g and foods rich in iodine should be encouraged as they will drastically reduce the problem of IDD and increase child growth, development, and survival.
The authors wish to thank the Network on Behavioral Research for Child Survival in Nigeria (NETBRECSIN) for technical support. We thank Mr. Igboji and Mr. Ogbonna of Ebonyi State Ministry of Health and Ebonyi State Primary Education board respectively for their logistic support.
Financial support and sponsorship
Conflicts of interest
The opinions expressed in this article are solely that of the authors and does not in any way reflect the opinion of their respective Institutions.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4]