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Iron profile and dietary pattern of primary school obese Egyptian children

Abd-El Wahed, Mohamed A.; Mohamed, Maha H.; Ibrahim, Samia S.; El-Naggar, Wafaa A.

The Journal Of The Egyptian Public Health Association: August 2014 - Volume 89 - Issue 2 - p 53–59
doi: 10.1097/01.EPX.0000451827.84315.5c
Original articles
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Background Poor iron status affects billions of people worldwide. The prevalence of obesity continues to rise in both the developed and developing nations. An association between iron status and obesity has been described in children and adults. The aim of the study was to assess the iron profile and dietary pattern in primary school-aged obese Egyptian children.

Materials and methods A case–control study was conducted on 120 children, both obese (n=60) and control group (n=60), recruited from three primary governmental schools located in Dokki Sector, El-Giza Governorate, Egypt. Their ages ranged from 6 to 12 years. All children were subjected to full medical and dietetic history, anthropometric measurements, thorough clinical examination, and determination of complete blood count, serum iron, total iron-binding capacity, transferrin saturation (TS), and ferritin.

Results Despite similar dietary iron intake in the two groups, obese children showed highly significantly decreased hematocrit, mean corpuscular volume, mean corpuscular hemoglobin, serum iron, and TS, and increased mean corpuscular hemoglobin concentration and total iron-binding capacity when compared with the nonobese group. The obese group showed a highly significant increased rate of iron deficiency (ID) (TS<15% or mean corpuscular volume<76 fl) when compared with the nonobese group. Obesity was a significant risk factor for the development of ID (odds ratio: 7.09, 95% confidence interval: 3.16–15.92).

Conclusion and recommendations The association between ID and obesity may have important public health and clinical implications. For primary school children with elevated BMIs, screening for ID should be considered. Increasing awareness of the importance of physical activity and carrying out nutritional education programs are required.

Department of Pediatric, Faculty of Medicine, Ain Shams University, Cairo, Egypt

Correspondence to Maha H. Mohamed, MD, Department of Pediatric, Faculty of Medicine, Ain Shams University, Abbassia Square, 11769 Cairo, Egypt Tel: +20 100 528 7175; fax: +02 262 01764; e-mail: dr_mhassan21@yahoo.com

Received February 24, 2014

Accepted June 10, 2014

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Introduction

Worldwide prevalence of childhood obesity has increased greatly during the past three decades 1. Iron deficiency (ID) is the most common form of nutritional deficiency in childhood, affecting all socioeconomic levels of society 2. ID is a major public health concern in preschool children and pregnant women in the developing world. Prevention of ID is crucial from a public health perspective, because it is associated with behavioral and cognitive delays in infancy and early childhood, such as impaired learning, decreased school achievements, and lower scores on tests of mental and motor development 3.

In USA, ID anemia is the most common cause of anemia in childhood. The incidence of ID is 5.5% in inner-city school children with age ranging from 5 to 8 years, 2.6% in preadolescents, and 25% in pregnant teenage girls 4. An association between iron status and obesity has been described in children and adults 5.

Obese children are at a risk of increased morbidity starting in childhood or adolescence. Despite their excessive dietary and caloric intake, obese children and adolescents may be at risk for ID and represent a new emerging risk group for ID beside other vulnerable age groups, such as infancy and early childhood 3. The etiology behind this relation is uncertain. Obese children, and adolescents particularly, may be at risk for ID because they tend to consume unbalanced meals, particularly rich in carbohydrates and fat. In addition, both obesity and ID are more prevalent in lower socioeconomic groups that consume low-cost fast foods, which are low in essential nutrients and rich in fats, sugars, and preservatives 6. Other contributing factors are poor iron intake, repeated short-term restrictive diets, increase in blood volume when children enter adolescence, early onset of menstruation, limited physical activity, rapid growth, and genetics 3.

Although many studies have examined preschool children and pregnant women as the most common at-risk groups, there is a paucity of data on iron profile in obese school children school children living in the developing countries. The aim of this study was to assess iron profile in primary school-aged obese Egyptian children in El-Giza Governorate.

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Materials and methods

A case–control study was conducted on children from three primary governmental mixed (male and female) schools located in El-Giza Governorate (Dokki Sector), Egypt. El-Giza Governorate is divided into 20 educational sectors, one of them being the Dokki Sector that contains eight primary governmental mixed schools. Enrollment was done by stratified randomization. Children were enrolled in the schools, where the initial examination took place, and then they were asked to come to outpatient clinics of the National Research Center where the study took place.

This study included 120 children, both obese and apparently healthy control group children from the same schools, sharing the same social class, who fulfilled our criteria, and agreed to participate in our study. Their age ranged from 6 to 12 years. A written informed and verbal uniform consent was obtained before the study from the students’ parents after full explanation of their role in the research. The study was approved by the Medical Ethical Committee of the National Research Center and the Ministry of Education.

Children were divided into two groups on the basis of BMI for age and sex. Diagnosis of obesity was based on BMI percentile growth charts developed by Centers for Disease Control and Prevention (CDC) 7.

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Cases

A total of 60 obese children were recruited from the selected schools with BMI of at least 95th percentile 1. Their obesity was due to nutritional causes (simple or exogenous obesity). There were 29 boys and 31 girls. Their age ranged from 6 to 12 years, with a mean age of 9.37±1.74 years.

Diseased children on regular or sporadic treatment causing alteration in lipid and glucose metabolism as corticosteroid therapy (autoimmune diseases and bronchial asthma), children with endocrinal causes of obesity (e.g. hypothyroidism, Cushing disease, and diabetes mellitus), children with obesity as part of a syndrome (such as Prader–Willi, Laurence–Moon–Biedl syndromes) were excluded. Children suffering from hemorrhage or receiving blood transfusion, with a history of iron supplementation, with jaundice during the previous 30 days, in addition to those with signs and symptoms of acute or chronic inflammation, were also excluded from the study.

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Control group

A total of 60 apparently healthy, control group children with BMI of 85th percentile or less 1, with age and sex matched to the cases, were recruited from the same schools and enrolled as a control group. They were 29 boys and 31 girls, with a mean age of 9.13±1.58 years.

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Data collection methods

All children enrolled in the study were subjected to the following.

  • Full medical history taking including personal history, manifestations of ID with or without anemia (easy fatigability, weakness, headache, lack of concentration, and palpitation), associated parasitic infestations, duration of obesity, and recording of regular physical activity. Past history of previous operation, hemorrhage, drug intake, vitamins and tonics, family history of obesity, endocrinal diseases, diabetes mellitus, and hypertension were enquired about.
  • Dietetic history: This was based on the food frequency pattern. The frequency of consumption of certain food items over a period of the last 12 months was assessed by the Food Frequency Questionnaire method 8. The Food Frequency Questionnaire included questions on the average consumption frequency during the previous year (never or rarely; times per month, week, or day). Those who consumed food items once per day or more were considered highly frequent intake, those who consumed food items less than once per day up to once per week were considered frequent intake, whereas those who consumed food items less than once per week or less were considered rarely or less frequent intake. High-glycemic index foods included sugar-sweetened soft drinks, bread, ready-to-eat cereals, potatoes, cakes, biscuits, rice, and macaroni, whereas low-glycemic index foods included milk and milk products. Information regarding eating habits included the number of main meals per day, eating between meals (snacks), quality of snacks, and application of dietary regimen.
  • Anthropometric measurements:
    • Weight (kg): It was measured by using the Tanita digital balance (Tanita Corporation of America, Inc., Illinois, USA). The balance was set on a hard, flat, and uncarpeted surface. It was taken to the nearest 0.1 kg.
    • Height (cm): It was measured using the Tanita stadiometer (Tanita Corporation of America, Inc., Illinois, USA) with the child standing without shoes, with his heels together without raising them, with the back straightened as possible, with his back against the scaled board of the stadiometer. The stadiometer was set on a hard, flat, and uncarpeted surface. It was taken to the nearest 0.1 cm.
    • BMI (kg/m2): It was calculated according to the following equation: weight/height21.
    • Waist and hip circumference measurements (cm): Waist circumference was measured at the narrowest point between the rib cage and iliac spine with minimum clothes after taking deep inspiration and then expiration, whereas the hip circumference was measured at the widest point for the buttocks. Both were measured using steel tape and were taken to the nearest 0.1 cm. The waist to hip ratio was then calculated.
  • Thorough clinical examination included signs suggestive of anemia (pallor, jaundice, glossitis or stomatitis, and nail abnormality). Arterial blood pressure measurement: Systolic and diastolic blood pressure was measured two times with mercury sphygmomanometer in the sitting position from the right arm, and the mean value of the two measures was taken.
  • Laboratory investigations:
    • Blood sampling and procedures: Blood samples were obtained by aseptic technique using vein puncture. About 5 ml venous blood was withdrawn from each child after overnight fasting (about 8 h) and divided into two parts. The first part was about 1 ml whole blood collected on EDTA plastic tubes serving as an anticoagulant for complete blood count (CBC) assay and blood film for reticulocyte count. Samples for CBC and blood film for reticulocyte were subjected for immediate assay (within 4 h). The second part was collected in plain plastic clean tubes without additives for serum iron, total iron-binding capacity (TIBC), and serum ferritin. It was kept at room temperature for 2 h, where it was allowed to clot, after which they were centrifuged and the serum was separated and kept in plastic Eppendorf tubes then frozen at −20°C till the time of assay. They include the following:
      • CBC was done on medonic CA620 (Balder Medical AB, Stockholm, Sweden) 9.
      • Reticulocyte count: Reticulocytes were counted in a blood film stained with new methylene blue, to count the cells. Ten successive fields were examined until at least 100 reticulocytes had been counted. Normal value ranged between 0.2 and 2% 10.
      • Determination of serum iron was done using Olympus AU 400 (Olympus corporation, Japan) 11. The reference value for serum iron for this age group of children is 70–180 µg/dl for boys, and 60–180 µg/dl for girls 12.
      • Determination of TIBC using kit produced by Spectrum (Spectrum Diagnostics, Egypt) 13. Reference value for TIBC for this age group of children is 200–380 µg/dl 12.
      • Transferrin saturation % (TS%) was calculated from the following equation: serum iron/TIBC×100 14. Reference value for this age group of children was greater than 15% 12.
      • Determination of serum ferritin by Ferritin Accu-Bind ELISA Microwells kit (2825-300) produced by Monobind Inc. (Monobind Inc., Lake Forest, California, USA) 11. Reference value for this age group of children was greater than 10 μg/ml 11.

ID with or without anemia was defined in this age group from 6 to 12 years if:

  • Mean corpuscular volume (MCV) is 76 fl or less 15.
  • Serum TS 15% or less 11.
  • Serum ferritin less than 10 μg/ml 11.

The presence of two or more abnormal parameters of iron status was considered indicative of impaired iron status 14.

Stool samples were collected in the same visit, if possible, or delivered to the laboratory room at the National Research Center on the next day by either the student or one of his parents and tested for the associated parasitic infestations.

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Statistical analysis

The data were coded, entered, and processed on computer using SPSS 15 (SPSS Inc., Texas, USA). Continuous variables were expressed as the mean±SD, and categorical variables were expressed as number and percentages (%). Student t-test of two independent samples was used for the comparison of normally distributed quantitative variables, and χ2-test was used for the comparison of qualitative variables. Adjusted odds ratios (ORs) with 95% confidence intervals (CIs) were computed. The probability of error less than 0.05 was considered significant, whereas at 0.01 and 0.001 were highly significant 16.

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Results

Demographic and clinical characteristics of the studied children are shown in Table 1. Obese children showed statistically significant increased weight, height, BMI, waist circumference, hip circumference, waist/hip ratio, and systolic and diastolic blood pressure compared with controls. The frequency of male distribution was comparable to female distribution in both groups. There were no statistically significant differences between cases and controls in terms of family history of obesity, diabetes mellitus, or hypertension.

Table 1

Table 1

Dietary history and physical activity among studied children is shown in Table 2. Obese children showed significantly increased frequency of eating anything available and the absence of physical activity than in the control group. The numbers of meals per day and snack intake were comparable in both groups.

Table 2

Table 2

Frequency of food consumption by studied children is shown in Tables 3 and 4. Obese children showed significantly higher frequency of eating food rich in starch and eating junk food than the control group. There was no statistically significant difference between cases and controls with regard to eating enhancers, molasses, phytates (nuts and bran), polyphynon (coffee and tea) cocoa, and milk.

Table 3

Table 3

Table 4

Table 4

Laboratory data of studied children are shown in Table 5 and Fig. 1. Obese children showed statistically significantly higher mean corpuscular hemoglobin concentration, white blood cells, reticulocytes %, TIBC, and highly significantly lower mean hematocrit, MCV, mean corpuscular hemoglobin, serum iron, and TS when compared with the control group. Cases and controls were comparable in terms of the mean red blood cells, Hb, red cell distribution width %, platelet count, reticulocyte Hb content, and serum ferritin. Frequency of parasitic infestation was comparable in the cases and control groups; Ascaris spp., Oxyuris spp., Entamoeba histolytica, and Giardia lamblia were the most frequent parasites. Obese children showed statistically significant higher rate of ID when compared with the control group (OR: 7.09, 95% CI: 3.16–15.92) (Table 6).

Table 5

Table 5

Figure 1

Figure 1

Table 6

Table 6

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Discussion

Nutrition in childhood has a significant impact on lifelong health. Obesity and ID are two of the most common nutritional disorders worldwide 6.

In the present study, obese children showed a highly statistically significant higher weight, mean height, BMI, waist circumference, hip circumference, and waist to hip ratio when compared with control. Previous studies reported that BMI is a reliable and preferable measure of adiposity in children and adolescence 17,18. The waist to hip ratio may be affected by the bulk of the gluteal muscles, which may give a false impression. Therefore, waist circumference may be a better indicator of central adiposity and is associated with cardiovascular risk factors independent of BMI 19.

In the present study, the mean systolic and diastolic blood pressure was significantly higher in obese when compared with nonobese children. The relationship between obesity and hypertension was shown in previous studies and has been demonstrated in children as young as 5 years old and young adults 20,21. Obesity-related hypertension can be explained by increased peripheral resistance coupled with high cardiac output and increased sympathetic nervous system activity. Obesity increases the cardiovascular risk for hypertension and metabolic syndrome by three-fold 22.

In our study, parasitic infestations were common. As its frequency was comparable in both groups, it was unlikely to be a direct cause of ID state. On the contrary, previous studies reported that in developing countries, blood loss due to parasitic infection or malaria is a common cause of ID. This could be explained by the fact that blood loss, reduced appetite, impaired digestion, and malabsorption may be the causes of poor iron status in children suffering from intestinal parasitic infestations 23.

With regard to the physical activity among studied groups, obese children showed infrequent physical activity compared with the control group. Moreover, it is believed that much of the increase in obesity in the last 25 years has resulted from the decreased level of physical activity in everyday life 24. Lack of daily, quality physical activity in all schools is proved to be one of the causes of obesity. Furthermore, the 2008 Physical Activity Guidelines for Americans recommended at least 60 min of aerobic physical activity each day, which is not approached by our children 25.

In our study, there was no significant difference between obese and control group children in terms of the number of main meals and snacks intake; however, obese children showed significantly higher rate of intake of eating anything available, less consumption of fresh fruits, and vegetables than the control group. Obese children had higher rate of consumption of food rich in starch and junk food than the non-obese group. This came in accordance with the previous studies that reported that overfeeding with snack food with high calories is one of the reasons for the rapidly increasing prevalence of childhood obesity 26,27. Snacking between meals has risen steadily over the last two decades, with many snacks being high in fat, sugar, or both 27.

In the present study, with regard to the diet frequency pattern, there was no statistically significant differences between obese and control group children, in terms of eating animal proteins, enhancers, molasses, or in the intake of inhibitors of iron absorption as phytates (nuts and bran), polyphynon (coffee, tea, and cocoa), or milk (inhibit iron absorption). As the frequency of dietary iron intake together with iron enhancers and inhibitors were comparable in both the groups, ID could not be directly explained by dietary intake. Similar studies supported the finding that ID in obesity is not due to deficient dietary iron 5,28–31.

In our study, obese children showed statistically highly significant lower mean hematocrit, MCV, mean corpuscular hemoglobin, serum iron, and TS, and increased TIBC, when compared with control group. Obese children showed highly statistically significant higher rate of ID when compared with the control group children. Obese children are likely to have ID six times as the nonobese group (OR: 7.09, 95% CI: 3.16–15.92).

An association between iron status and obesity has been described in children and adults. The mechanism explaining this relationship remains unknown; however, findings from recent reports suggest that the bioavailability of iron may be modulated by factors linked to chronic inflammation induced by excess adiposity. In particular, the increased levels of inflammatory cytokines found in obese individuals have been inversely associated with serum iron levels 30. Moreover, BMI and inflammation predict iron absorption and affect the response to iron fortification 32,33. The relationship between inflammation and iron absorption may be mediated by hepcidin, the main regulatory hormone of iron absorption and recirculation. Hepcidin levels, induced by inflammatory cytokines, were higher in overweight children, adolescents 29,34,35, and adults 30 compared with their normal weight peers. Moreover, BMI reduction is associated with hepcidin reduction, potentially improving iron status and absorption 36. As ID in obese children in our study could not be directly related to dietary iron, it may be due to subclinical inflammation. This possible cause is supported by the findings of previous studies 15,37,38. On the contrary, others reported that in developing countries, ID is usually related to reduced weight and poor growth rate 39.

Although ferritin levels are decreased in cases of ID state, serum ferritin levels were comparable in both obese and control groups in our study. Ferritin is considered an acute-phase reactant; hence, it may be elevated in inflammatory conditions even in the presence of true ID 40. Cytokines such as interleukin-1β and tumor necrosis factor-α induce ferritin production within macrophages, hepatocytes, and adipocytes 31. Considering that obesity represents such a state, the increased levels of serum ferritin in overweight and obese children may lead to an underestimation of the true magnitude of ID in this population. This hypothesis is supported by previous studies that showed that the prevalence of ID and iron deficinecy anemia was lower when using serum ferritin as a diagnostic criterion compared with using transferrin saturation 30,31,40.

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Limitations of the study

Obese and nonobese participants of the study were recruited from the same schools sharing the same culture, social class, and economic status, not representing Egypt or even Giza Governorate. The small sample size is another limitation.

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Conclusion

We found increased frequency of ID state among obese school-aged children than control groups, despite comparable dietary iron intake. This may have important public health implications.

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Recommendations

For primary school children with elevated BMIs, screening for ID should be considered. Increasing the awareness of importance of physical activity and carrying out nutritional education programs is required.

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Acknowledgements

Conflicts of interest

There are no conflicts of interest.

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Keywords:

BMI; iron deficiency; obesity; school-aged children; serum ferritin; serum iron; transferrin saturation

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