1.1 Background to the Study
Iodine is an essential mineral required by the body to synthesize thyroid hormones (thyroxine and triiodothyronine). The most important of which is thyroxine, a metabolism regulating substance (Kennedy, Nantel & Shetty,2003). The trace element (iodine) is an essential nutrient for human growth and development.
The daily recommended intake of iodine for school children (6-12yrs) is 120mcg/day (WHO/UNICEF/International Council for Control of Iodine Deficiency Disorders (ICCIDD), 2007). Iodine deficiency disorders are primarily the result of inadequate amounts of iodine in the soil, water and food as well as consumption of foods rich in goitrogenic substances (Ene-Obong, 2001). Apart from intake of goitrogenic and inadequate amounts of iodine, other factors are known to interfere with adequate iodine nutrition and these include protein energy malnutrition (Brahmbhatt et al., 2007), and vitamin A deficiency (ACC/SCN, 1994). The world’s natural supply of iodine is mostly from the ocean in the form of iodide. The adequacy of dietary iodine is usually determined by the measurement of urinary excretion of iodine (Lee, Bradley & Dwyer, 1999). The commonest manifestation of iodine deficiency is goiter. It occurs when the iodine level of the blood is low; the cells of the thyroid gland enlarge in an attempt to trap as many particles of iodine as possible. Sometimes the gland enlarges until it is visible as a swelling in the anterior part of the neck (Chatterjea & Rana, 2004).
Inadequate dietary iodine leads to reduced synthesis of thyroid hormones (Thyroxine (T4) and Triiodothyronine (T3)). A lower level of T4 stimulates the pituitary gland to stimulate thyroid stimulating hormone (TSH) to fulfill the production of thyroid gland hormones. It is important not to over consume iodine as it has a relatively narrow range of intakes that reliably support good thyroid function. Consumption of an excessive amount of iodized salt or seaweeds could readily result to complex disruptive effect on the thyroid gland and may cause hyperthyroidism in susceptible individuals, as well as increasing the risk of thyroid cancer (Chatterjea & Rana, 2004).
The supply of adequate iodine in the diet and the elimination of goitrogens are ways to prevent endemic goitre. However, there is increasing evidence that endemic goitre could be provoked by genetic as well as environmental factors including emotional stress, smoking and infections (Abuye, Omwega & Imungi, 1999).
Iodine is an important micronutrient required for proper brain development. One of the millennium development goals (MDG) of the United Nations is to reduce child mortality by 2015 (Andy & Andrew, 2004). Severe iodine deficiency in the mother has been associated with miscarriages, still births, preterm delivery and congenital abnormalities in their babies (Benoist, McLean, Anderson & Rogers, 2008). Iodine deficiency in its most extreme form, results in cretinism. Of much greater public health importance, are more subtle degrees of brain damage and reduced cognitive capacity, which could affect the whole population (World Health Organization (WHO), 2001). Iodine is the world’s leading cause of mental retardation. More than two billion children suffer from lowered intelligent quotient (IQ) and retardation due to iodine deficiency (United Nations Children’s Fund (UNICEF), 2002). Iodine deficiency disorder can be corrected by re-supplying iodine in the diet (Delange, 2000). The impact of IDD is enormous and it affects all the stages of life (ICCIDD/UNICEF/WHO, 2001).
As part of the strategies to reduce the prevalence of IDD in Nigeria, the universal salt iodization (USI) program was introduced in 1995. In most countries of the world, universal salt iodization has been employed as a means of eliminating disorders secondary to iodine deficiency. WHO, UNICEF and ICCIDD has brought iodine sufficiency within reach of about 1.5 billion people of the world who were deficient decades ago; and now rely on the urinary iodine concentration as the primary indicator of effectiveness (WHO, ICCIDD, 1999). In Africa and indeed Nigeria, great progress has been made towards the elimination of iodine deficiency saving millions of children from its adverse effects, largely due to the increased household availability of iodized salt (ICCIDD, 2003; WHO, 2007; Lantum, 2009).
Most iodine absorbed in the body eventually appears in the urine; therefore, urinary iodine concentration is a good marker for very recent dietary iodine intake. Urine iodine excretion is a good biomarker of dietary intake of iodine over days and is the measure of choice for assessment of iodine status (WHO/UNICEF/ICCIDD, 2007). For epidemiological studies, a population distribution of urinary iodine is required and, because the frequency distribution is typically skewed towards high values, the median rather than the mean is judged the best indicator of iodine status. WHO, ICCIDD, and UNICEF (2007) recommend that for national surveys of iodine nutrition, the median urinary iodine from representative samples of spot urine collections from children aged 6—12 years can be used to define a population’s iodine status. School-age children 6-12 years old form a useful study group for assessing iodine deficiency because of their physiological vulnerability to disease, their accessibility through school and a representation of iodine deficiency disorders (Joshi et al, 2006). In Nigeria, the National Agency for Food and Drug Administration and Control (NAFDAC) has greatly promoted salt iodization using public campaigns (Lantum, 2009).
In many developing countries, however, children hardly grow to their full potential as a result of many environmental factors such as malnutrition and infections (Van de Poel, Hosseinpoor, Speybroeck, Van ourti & Vega, 2008). Children from poor or less privileged families in those countries are the most affected due to food insecurity, inadequate facilities, infection and poor general environmental sanitations. The causes of child under nutrition are complex, multidimensional, and interrelated, ranging from factors as fundamental as political instability and slow economic growth to those as specific in their manifestation as respiratory infection and diarrhea disease (ACC/SCN, 2000). Lack of progress to combat malnutrition is damaging to children and nations. For every visibly undernourished child, there are several more, battling a hidden nutritional crisis. Many are seriously deficient in essential vitamins and minerals such as Iodine, Vitamin A and Iron (Clements, 2006).
This study was therefore carried out to assess the iodine and anthropometric status of primary school children in a Nigerian community, Okpuje.
1.2 Statement of the Problem
IDD is a serious public health problem in developing countries. It is one of the oldest and most insidious of human health problems. WHO (2011) estimated that two billion people worldwide including 285 million children of school age have iodine deficiency despite major national and international efforts to increase iodine intake, mainly through voluntary or mandatory intake of salt (WHO, 2011). Recent estimates by the World Health Organization (WHO, 2011) indicate that 54 countries are still affected by iodine deficiency and nearly 2 billion individuals worldwide are iodine-deficient. A large percentage of the world population is at risk of iodine deficiency disorder (IDD) (Delange & Hetzel, 2003). Poor nutrition remains a global epidemic contributing to more than half of all children’s deaths, about 5.6 million per year. It has been known that as severity of iodine deficiency increases, the occurrence of poor pregnancy outcome such as miscarriage, still birth, and increased infant mortality is more likely (Bruno & Maria, 2004).
Several parts of Nigeria have been identified with goitre endemicity and labeled the “goitre belt” (Abua, Ajayi & Sanusi, 2008; Isichie et al., 1987; Olurin, 1975; Nwokolo & Ekpechi, 1966). In 1993, a National goitre rate of 20% was reported and 20 million Nigerians were estimated to be affected by IDD (UNICEF, 1993). The Participatory Information Collection Study (1993), using thyroid hormone concentrations as indicators of iodine status reported an iodine deficiency prevalence of 65.6% in south-east, 41% in south-west, 43% in the north-west of Nigeria. Surveys found that the population in Nigeria affected by goiter prevalence in 30 states dropped from 40 million in 1990 to less than 11 million in 1999 (IDD Newsletter, 2000).
Enugu State in south east and Kogi state in south western Nigeria has long been identified as a goiter endemic area with a goiter prevalence rate of 16-40% (Egbuta, Onyezili & PHN 2002). Nwamarah and Okeke (2012) reported an iodine deficiency prevalence of 58.3% among school children in Obukpa, a community in Nsukka, Enugu state. Okpuje situated in Nsukka is mountainous, where the top layer of the soil has been eroded for decades leading to leaching away of nutrients including iodine. This made the people prone to iodine deficiency.
1.3 Objectives of the study
General objective: This is to assess iodine and nutritional status of primary school children in a Nigerian community, Okpuje.`
The specific objectives of the study were to:
i) determine the anthropometric indices of the school children;
ii) assess the clinical signs of malnutrition common among the children;
iii) assess the food consumption pattern of the children using 24hour dietary recall and food frequency questionnaire;
iv) assess the iodine levels of salt sold in Okpuje market; and
v) assess the iodine levels of salt used in respondents’ homes;
vi) assess the iodine status of the children using biochemical method;
vii) determine the relationship between the children’s iodine status and iodine levels of salt consumed; and
viii) determine the relationship between the iodine status and anthropometric indices of the children.
1.4 Significance of the study
It is hoped that the result of this study when published would provide information on the current iodine status of school-age children in Okpuje. The results of this study will assist in determining if study area is a vulnerable area for health and nutrition intervention. This will serve as a baseline data upon which intervention programmes can be instituted.
The results of this study when disseminated will be useful to the Nigerian government, National Agency for Food and Drug Administration and Control (NAFDAC), UNICEF, Nutritionists, health workers, groups and organizations concerned with the welfare of children who are interested in the assessment of the prevalence of micronutrient deficiency in Nigeria. It will identify some children who are at risk of iodine deficiency so as to ensure proper monitoring and assessment of table salts (NAFDAC), advocacy of balanced diet consumption (Nutritionists), and periodic monitoring of iodine nutriture (UNICEF).