ABSTRACT
This thesis investigates the level of iodine consumption in Zariametropolisusing individual duplicate diet assessment, total diet assessment and food frequency questionnaire. The project also includes the study of transfer of iodine from soil to crop in some selected plants, and the determination of iodine contents of table salt. Standard spectroscopic and radiochemical neutron activation techniques were used for iodine determination in the samples and the results obtained were validated by the use of standard reference materials. The concentrations range from 0.14 ± 0.04 to 2.04 ± 0.11mg/ kg, with meanconcentration of1.30mg/kg in duplicate diet sample, while that of total diet range from 0.30 ± 0.05 to 2.09 ± 0.08 mg/ kg, with meanconcentration of 1.43mg/kg.The iodine consumption per day range from 224 to1165 mg/day and 464 to 2237 mg/day for duplicate and total diet respectively.Iodized table salt was found to contain iodine from 14.87 ± 0.51mg/ kg to 74.78 ± 0.59 mg/ kg with a mean of 41.89mg/ kg.The results indicates that the studied population’siodine dietary intake meets the recommended daily allowance(150μg/day) of the WHO and ICCIDD. However, the iodine intake level is also too close to the upper tolerable intake level(1100μg/day) advised by the WHO.
TABLE OF CONTENTS
Title Page ————————————————————————– I Declaration ————————————————————————– II Certification ————————————————————————– III Acknowledgements ————————————————————————– IV Dedication ————————————————————————– V Abstract ————————————————————————– VI Table of Contents ————————————————————————– VII List of Tables ————————————————————————– X List of Figures ————————————————————————– XI List of Appendices ————————————————————————– XII List of Plates ————————————————————————– XIII List of Abbreviations ————————————————————————– XIV
1.0 INTRODUCTION
1.1 Background —————————————————————– 1
1.2 History —————————————————————– 3
1.3 Policies —————————————————————– 4
1.4 Research Problem —————————————————————– 5
1.5 Justification —————————————————————– 7
1.6 Aim and Objectives ——————————————————– 9
1.7 Research Hypothesis ——————————————————– 9
viii
2.0 LITERATURE REVIEW
2.1 Iodine determination ———————————————– 10
2.2 Theory of Analytical Method ——————————————————– 14
2.3 Detection and Counting ——————————————————– 17
3.0 MATERIAL AND METHODS
3.1 Materials —————————————————————– 18
3.1.1 Description of Study Area ——————————————————– 18 3.1.2 List of Apparatus and Equipment ———————————————- 20
3.1.3 Preparation of Reagent ——————————————————– 20
3.1.4.0 Sampling ——————————————————– 21 3.1.4.1 Sample Collection ——————————————————– 22 3.1.4.1 Sample Peparation ——————————————————– 23
3.2.1 Methods —————————————————————— 32
3.2.2 Instrumental Neutron Activation Analysis ————————————- 32
3.2.3 Pre-concentration Neutron Activation Analysis ——————————- 33
3.2.4 Spectroscopy ——————————————————– 36
3.2.3.1 Alkaline Dry Ashing———————————————————— 36 3.2.3.2 Microwave Assited Acid Digestion ———————————————– 36
3.2.5 Iodometric Titration ——————————————————– 39
ix
4.0 RESULTS
4.1 Recovery ExperimentsResults ——————————————————– 43 4.2 Samples Analysis Results ——————————————————– 51
5.0 DISCUSSIONS
5.1 Quality Assurance —————————————————————– 60 5.2 Food Samples —————————————————————– 61 5.3 Farm Soil and Produce —————————————————————– 68 5.4 Iodine Titrimetry —————————————————————– 68 5.5 Dietary Assessment Questionnaire ——————————————————- 70
6.0 CONCLUSION AND RECOMMENDATIONS
6.1 Conclusion ————————————————————————– 71 6.2 Recommendation —————————————————————– 72 Reference ———————————————————————————– 73 Appendix ———————————————————————————– 80
CHAPTER ONE
1.0 INTRODUCTION
1.1 Background
Micronutrients are required by humans throughout life in small quantities to coordinate a
whole range of physiological functions which the body cannot do without (World Health
Organization (WHO), 1996). These micro nutrients include iron, cobalt, chromium, copper,
iodine, manganese, selenium, zinc, molybdenum and vitamins. They are generally required in
less than 100 milligrams per day, and as such are termed dietary trace minerals (WHO, 1996;
WHO / FAO, 1998). The human body only needs 150 micrograms (or 20,000th of a
teaspoon) of iodine to meet daily requirement and not more than a teaspoon full in an entire
lifetime (WHO, 1996).
Iodine is an essential component in the synthesis of L-monoiodotyrosine, which is a precursor
of the thyroid hormones, thyroxine (T4) and triiodothyronine (T3), comprising 65 and 59
percent of their respective weights (Ahmed et al. 2008). The thyroid hormone T4 and T3
regulate many key biochemical reactions, particularly protein synthesis and enzymatic
activity. Major target organs are the developing brain, muscle, heart, pituitary gland, and
kidney (Ahmed et al., 2008).
H2N
HO O
OH
H
l-monoiodotyrosine
I
OH
I I
H2N COOH
I
thyroxine (T4)
I
OH
I
H2N COOH
I
triiodothyronine (T3)
Figure 1: Thyroid hormones
2
Thyroid hormones, and therefore iodine, is essential for mammalian life, as without sufficient iodine, the body would be unable to synthesize these hormones, and since the thyroid hormones regulate metabolism in every cell of the body and play a role in virtually all physiological functions, iodine deficiency can have a devastating impact on health and well-being which is summarily termed Iodine Deficiency Disorders (IDD) (International Council for Control of Iodine Deficiency Disorders, 2011).Iodine deficiency is the single most common cause of preventable mental retardation and brain damage in the world (De Maeyeret al., 1979, ICCIDD, 2011). Several other physiological functions of iodine have been suggested (ICCIDD, 2011).Iodine plays a role in the prevention of fibrocystic breast disease, a condition characterized by painful swelling in the breasts. Research work by Dijkstraet al. (2010) indicates that iodine is involved in controlling the effects of estrogen on breast tissue. It is used in fibrocystic breast disease for mitigating and even overcoming the impact of the medical condition (Dijkstraet al., 2010). Diets deficient in iodine increase risk of retarded brain development in children (cretinism), goitre (Hetzel and Mark, 1989), mental retardation (Hetzel and Mark, 1989; Hetzel, 2000), high cholesterol (Takeo et al. 1963), fatigue and depression (Verse and George, 1935; Takeo et al., 1963), lethargy (Hetzel, 2000), and weight gain (Syed et al., 2001; Loireauet al., 1987). Cretinism is a severe iodine deficiency disorder that causes mental retardation while goitre or swelling of the thyroid gland results in inhibition of immune system function, dry skin, excessive estrogen production and hypothyroidism (Hetzel, 2000).
Iodine deficiency in pregnant women can lead to neurocognitive deficits in the children. Stunted growth, apathy, impaired speech and hearing problems may also develop due to this deficiency (ICCIDD 2011). Iodine is also an important element that determines the health of
3
connective tissues in fetuses (Perkeret al., 1951).Parkinson’s disease, multiple sclerosis and Alzheimer’s disease have also been linked with iodine deficiency (International Medical Veritas Association, 2011). Consumption of minerals such as magnesium, manganese, calcium, and fluoride can restrict the absorption of iodine uptake by the thyroid gland. Like under-consumption, too much iodine prevents proper production of thyroid hormones leading to iodine induced hyperthyroidism with similar manifestation to IDD (Kennedy, 1942). The toxicity from iodine depends on its concentration level and the amount of food taken (Brittmarie, 1998). In a balanced diet, the recommended daily intakes of iodine for a normal adult is 100–150 μg per day. In the presence of goitrogens in the diet, the intake should be increased to the range of 200–300 μg per day (WHO, 1996). Information about the proper amount of iodine according to age is given below. Table 1.1: Dietary reference intake for iodine
Age (years)
Recommended Daily Allowance, RDA.(μg)
Tolerable Upper Intake Levels (μg)
0-6 months
110
ND
7-12 months
130
ND
1 – 3
90
200
4 – 8
90
300
9 – 13
120
600
14 – 18
150
900
19+
150
1100
Pregnant
220
1100
Lactating
290
1100
Institute of Medicine, Food and Nutrition Board, 2001. ND = Not determinable due to lack of data of adverse effects in this age group and concern with regard to lack of ability to handle excess amounts. 1.2 History
Iodine (Greek; iodes, meaning violet) was discovered by Barnard Curtois in 1811. He was destroying seaweed waste after extraction of nitrate for gun powder production when he
4
accidentally added too much sulfuric acid. Curtois observed a cloud of purple vapor and he noted that the vapour crystallized on cold surfaces making dark crystals (Moehlmann, 2005). Endemic cretinism, a condition that was well known in Alpine Europe in the Middle-Ages was mentioned in Diderot’s Encyclopedia in 1754 and was of such importance as to warrant a special commission to be set up by the King of Sardinia in 1848 (Hetzel, 1989). The demonstration for the prevention of cretinism in a double-blind controlled trail with iodized oil in Papua New Guinea established the causal role of iodine deficiency in cretinism by an effect on developing fetus (Pharoahet al., 1971). Federal Ministry of Health Nigeria, in 1974 formed a Ministerial Committee on iodization of salt. This committee wound up after two years due to poor funding. Efforts from Non-Governmental Organizations (NGO) and individuals led to a meeting of Ministerial Expert Committee on IDD in 1988 to consider the iodization problem again. However, the committee went into abeyance, due to administrative and funding problems again (Hetzel 1989). Early studies showed that IDD was a public health problem in Nigeria (Ekpechi, 1967; Ekpechi, 1973; Ekpechiet al., 1996). The prevalence of IDD in Nigeria was established by the measurement of total goitre rate which was put at 20% acroos the nation (Egbuta, 2002). 1.3 Policies
The UNICEF (2008) reported that Standard Organization of Nigeria (SON), in 1992, mandated that all table salt should be iodized with 50ppm potassium iodide at packaging stage. This standard was reviewed based on evidences from Universal Salt Iodization (USI) programs worldwide on loss of potassium iodide, especially when sold in bulk in open air markets. The new standard for food grade salt, required potassium iodate to replace
5
potassium iodide so as to improve retention. The revised SON standard also established packaging to be in 50g retail bags. The new standard defines properly iodized salt as:
i. Greater than 50 ppm iodine at port of entry and salt factory level
ii. Greater than 30 ppm iodine at distributor and retail levels and
iii. Greater than 15 ppm iodine at household level
Codex standard for food grade salt as revised in 1997 and amended in 1999, 2001 and 2006 requires that in iodine deficient areas, food grade salt should be iodized to prevent iodine-deficiency disorders for public health reasons. It also suggested that, the use of sodium and potassium iodides or iodates for the fortification of salt, as well required that maximum and minimum levels used for the iodization of food grade salt are to be calculated as iodine expressed in mg/kg and be established by the National Health Authorities in the light of the local iodine deficiency situation (CX STAN 150:1985). 1.4 Research Problem Iodine in its natural form is available in food. However, the quantity of iodine in the food is directly proportional to those obtainable in the soil and water of the region (Aston and Brazier, 1979: Pennington, 1990). Mountainous regions and regions with heavy rainfall tend to have very little iodine contents in the soils (Pennington, 1990). As a reference, the level of iodine in foods such as fish, shellfish, meat, milk, cereal grains, fruits, and vegetables were in the range of 30–4990 mg/kg, with sea foods having the highest concentration (Koutras, 1986).
6
Table 1.2: Iodine content of some food.
Food
Serving Size
Amount (μg)
% RDA Value
Sea Vegetables
0.25 cup
415.00
276.60
Yogurt
1 cup
87.22
58.10
Milk
1 cup
58.56
39.00
Eggs
1 each
27.00
18.00
Strawberries
1 cup
12.96
8.60
Cheese
1 oz.
10.09
6.70
Whole bread
1 slice
1.95
1.30
Chicken/ Turkey
1 oz.
175.00
116.67
Orange (navel)
1 each
0.60
0.40
Retrieved from Kautras, 1986. Considering the reported success and ongoing efforts of Universal Salt Iodization (USI) program in Nigeria, some global stakeholders assert that it is difficult to concur that household access to iodized salt is at the elevated levels (United Nations Children and Education Fund (UNICEF), 2008; ICCIDD, 2005). Although salt iodization is an important strategy in the management of iodine deficiency disorders, dietary habit is a major problem of salt iodization. High dietary salt is considered to cause about 30% of cases of hypertension (Committee on public Health, 2011). IDD result, primarily from insufficient amounts of iodine in soil (Aston and Brazier, 1979), food and animal feed (Kennedy, 1942) as well as consuming foods rich in goitrogenic substances such as cassava, soybeans, peanuts, millet, spinach, sweet potatoes, rapeseed (Sharplesset al.,1943; Moudgalet al.,1958). It is important to note that excessive consumption of iodine can be toxic and just as damaging as a deficiency since the intake of as little as 1000 micrograms of iodine in a day causes irritations like burning of the mouth and throat, nausea, vomiting, stomach ache, and even coma (Salockset al., 2003).
It is now clear that the effects of iodine deficiency on human health are much greater than previously thought because of the extensive occurrence of hypothyroidism and its effects on
7
physical and mental development. All these effects can be prevented by the correction of iodine deficiency (Hetzel, 1983).
1.5 Justification
Human micro-nutrition deficiency appears to be much more widely spread than previously thought and it should be noted that human nutrition is analogous to plant nutrition. The World Health Organization, estimates that over three quarter of a billion people are suffering from iodine deficiency disorders (ICCIDD, 2011). Iodine deficiency in pregnant women causes miscarriages, stillbirths, and other complications. Children with IDD can grow up stunted, apathetic, mentally retarded, and incapable of normal movements, speech, or hearing. Globally, 2.2 billion people (38% of the world’s population) live in areas with iodine deficiency and risk its complications (ICCIDD, 2011). Fifty percent of the population in Nigeria lives in rural areas. Malnutrition in children is high, 29 percent are underweight, and 38 percent suffer from stunting (Food Agricultural Organization (FAO), 2011). Nigeria has the largest index of childhood mortality in Africa and the 6th largest in the world (FAO, 2011). The entire landscape of Nigeria predisposes the country to iodine deficiency disorders because of its proximity to the Equator and the long months of rainfall spreading from April to November (Nwokolo and Ekpechi, 1996: Egbutaet al., 2002). The risk of IDD is quite high in Nigeria, it has a well demarcated goiter belt, where almost all the inhabitants within the belt live on cassava based food staple. At least 60 million Nigerians (from a total population of 140 million) are at risk of IDD. (Egbuta and Hettiaratchy, 1995).
Iodine and other trace elements naturally occur in the soil but erosion leaches off these elements from the soil. Soils with less vegetative cover and locations susceptible to erosion loses their iodine concentrations through the wash up and leaching (Pennington, 1990). A
8
study on reported goitrous area in Jos plateau shows that the water used for drinking and cooking is low in iodine, other halides and their compounds, but high in mineral contents, including calcium, magnesium, nitrate, chloride and total hardness (Ubom, 1991). Similarly, comparative studies at a community prone to soil erosion, Nanka with nearby Oba (both in Anambra State) to serve as control, shows that Nanka has 14% less iodine in drinking water and 8% less in mean urinary iodine concentration of school children. However, the results indicated that both communities could be at risk of IDD (Orisakweet al., 2007). Mapping of livelihoods and nutrition in Nigeria reported that some state such as Abia, Adamawa, Bayelsa, Borno, Delta, Niger have no risk of IDDs, while some states indicate risk at only a few local government areas (L.G.A.) such as Ebonyi with only 4% possible iodine deficiency at Abakaliki L.G.A. and Sokoto with Kware L.G.A. showing 18.50% possible iodine deficiency in its population. AkwaIbom and Kaduna States show possible iodine deficiency in quite a number of L.G.A.s ranging from 10.5 to 29.5 % and 3 to 55.5% with a mean of 9.23% and 12.66% respectively. Bauchi and Oyo states show greater risk of IDDs in the population with an average of possible iodine deficiency at 34.15% and 32.23% respectively. Jigawa state is at most risk with all L.G.A.s (except Gwaram) showing possible iodine deficiencies in their population ranging from 5 up to 100% with a mean of 57.5% (Legg et al., 2002). Population suffering from iodine deficiency should be supported by more iodine, especially in the form of iodized salt, iodized oil and iodized flour. Iodine supplements are required for the synthesis of thyroid hormones and for correcting neurological, gastrointestinal and skin abnormalities in human beings (Hetzel, 2000).
However, an acute increase in iodine intake when there is chronic iodine deficiency is associated with risk of developing iodine induce hyperthyroidism. That is why the iodine
9
concentration range (130 to 1100 μg/day) in the diet is very important for public health (WHO, 1996).
1.6 Aim and Objectives
The aim of this research is to study the iodine contents of some commonly consumed foods in Zaria metropolis. The aim of the study was achieved through the following set objectives: Determining the iodine contents in foods consumed by the people of different economic status (income) in Zaria metropolis. Determining the concentrations of iodine in agricultural soil, crops, vegetables and foods. Comparing the iodine contents in local diets with the Required Dietary Intake (RUI). Identifying the foods that are rich in iodine. Compare the results obtained with Recommended Daily Allowance (RDA) and Upper Tolerable Intake Level (UTI).
1.7 Research Hypothesis The Study was guided by the following Null Hypothesis
i. There is no significant difference in the iodine concentrations of local and continental diets.
ii. There is no significant difference in the iodine intake among people with different incomes.
iii. Iodine in food is solely supplied by iodized salt.
10
Do you need help? Talk to us right now: (+234) 08060082010, 08107932631 (Call/WhatsApp). Email: [email protected].
IF YOU CAN'T FIND YOUR TOPIC, CLICK HERE TO HIRE A WRITER»
