Malnutrition, protein-energy malnutrition and micronutrient deficiencies continue to be major health burdens in developing countries, particularly in sub-Saharan Africa. It is globally one of the most common risk factor for illness and death, with hundreds of millions of pregnant women and young children particularly affected [36
]. For children in developing countries, malnutrition is a considerable health problem with prevalence rates estimated to range from 4% to 46% with 1% to 10% severely malnourished [37
]. The results of this study show that the prevalence of stunting observed among school children was 23%, which was in agreement with a finding from the study conducted among preschool children (24%) in northwest Ethiopia [38
]. However, it was much lower compared to previous findings in Gumbrit (50%) in Ethiopia [39
]. Higher prevalence of stunting were observed among school children in Tanzania (42.5%) [40
], and in Malaysia (40.2%) [41
The prevalence of stunting remains high in the area and the fact that the prevalence of stunting is much higher than that of underweight and wasting confirms that the major problem is chronic malnutrition. Since, stunting is a type of chronic malnutrition which begins in childhood, supplementing the infants and children with quality complementary food after 6 months of age and at least until age 36 months is required so as to minimize the long-term negative consequences of chronic undernutrition. In addition, investment in sustainable food-based strategies is urgently needed to combat hunger and micronutrient deficiencies [42
In this study, the prevalence of underweight (21%) was lower than previous reports from north-western Ethiopia [38
]. Both stunting and underweight were worsened as the study population got older, particularly for boys. This may lead to delayed onset of puberty in the boys. In addition, wasting which is usually caused by a relatively recent illness or food shortage was lower than stunting or underweight indicating that chronic malnutrition is more prevalent in Ethiopia than acute malnutrition.
In the present study, although not statistically significant, a positive correlation was observed between height-for-age z-score and serum iron levels (r=0.139, p
>0.05). It was also demonstrated that severely stunted school children had low serum concentrations of iron when compared to normal children. This observation was also observed by other authors [43
]. Less intake, poor absorption and the systemic effect of infection and utilization of iron by microorganisms for its growth and multiplication may be responsible for their lower iron status [44
]. We did not observe iron deficiency in school children irrespective of sex and helminths infection. A previous study involving children in Ethiopia included a thorough assessment of dietary intake and showed that dietary iron was adequate [45
]. Some crops, notably teff
, a staple dish of many people in the study area, are high in iron [46
] and fermented enset
may increase non-heme iron absorption [47
]. Moreover, intake of meat which is a source of heme iron in urban areas of the country is good [48
]. Heme iron is not only well absorbed than non-heme from plant source food, but also has an enhancing effect on absorption. because of exposure to high iron intake. Non-nutritional factors may be responsible for the anaemia seen in parts of the country.
Magnesium is important in maintaining several cellular functions as it is a natural activator of most enzymes. Magnesium deficiency frequently develops in a wide variety of clinical conditions such as protein–energy malnutrition malabsorption, hypoalbuminaemia, sepsis, hypothermia, etc., conditions that are commonly seen in children in developing countries [17
]. In the current study, deficiency in magnesium was observed in the school children of the present study, as 2% of them had its serum levels <1.80 mg/dl, particularly in boys. However, this prevalence is much lower than the 20.7% [19
] and 51.9% [49
] deficiency reported in Mexican and Vietnamese children. In addition, consistent with previous study in India [50
], serum magnesium levels had significant positive correlations with height-for-age. Lower serum magnesium levels in malnourished children may be due to inadequate intake, malabsorption, diarrhoea, and infection.
The present study demonstrated that normal and high calcium levels were common in school children, deficiency occurred in none of study subjects. This is not in agreement with reports from India and Nigeria [13
]. A possible explanation for the high serum calcium in our study area may be due to high calcium intake and sun exposure. The staple dish of many people in the study area and its environs is a pancake named enjera
made from a cereal called Teff
) which has higher calcium than those of wheat, barley, or sorghum [51
]. On the other hand, Ethiopia is located in the tropics in the horn of Africa between 3º and 15º N, 33º and 48º E where there is a large amount of sun exposure. When sunlight is plentiful, relatively high serum 25-hydroxyvitaminD3 may give rise to higher serum calcium levels [52
]. Ultraviolet light is essential in this reaction. It is worth mentioning that, during infection, macrophages and other immune cells can express 1α-hydoxylase, the enzyme that converts circulating 25(OH) D3 into 1,25(OH) D3, the active form of vitamin D [53
] and increased 1, 25(OH) D3 synthesis may further contribute to increased serum calcium level.
The high prevalence of zinc deficiency among the children has a far-reaching implication, as zinc is an important element performing a range of functions in the body. Zinc is a co-factor for the synthesis of a number of enzymes, DNA, and RNA [12
]. Zinc deficiency has been associated with poor growth in childhood, reduced immuno-competence, and increased infectious disease related morbidity [52
]. The findings of this study were in agreement with previous studies which have demonstrated the existence of zinc deficiencies among children of school age and early adolescence [55
]. Several studies globally have documented the relationships between lowered zinc concentrations during childhood and morbidity from infectious diseases and the effect on cognitive development [58
According to WHO, when the prevalence of zinc deficiency is greater than 20%, intervention to improve zinc status is recommended [59
]. As a result, the study recommends planning of sustainable community-based intervention strategies to improve the zinc status of school children through zinc supplementation and fortification of staple foods with zinc are recommended. These interventions are imperative in view of the well-known adverse consequences of zinc deficiency to the health and quality of life of school-aged children, particularly in terms of academic performance.
The mean level of copper in children of this study higher than those reported for children residing in Khartoum, Sudan [23
], for 10–12 years girls of urban Yemeni [60
], and for healthy Japanese children [24
]. The increased copper levels in serum may be due to a non specific increase in serum concentration of cooper binding protein, ceruloplasmin during acute-phase response against a variety of infections and inflammatory conditions [23
It is interesting to note that the determination of the copper/zinc ratio has been considered helpful in reflecting the nutritional status of zinc in the human body, better than its content in serum [61
]. It was also suggested that the copper/zinc ratio have diagnostic and prognostic values; if the ratio of copper/zinc exceeds 2 (Tables &), it would indicate severity of the infection [61
]. In the present study, the ratio of copper/zinc was higher in serum of school children with severe nutritional status.
Like zinc and magnesium, a significantly low level of serum selenium was observed in school children compared to the study in Iran [26
]. We observed selenium deficiency in a large number of school children (62%) and A negative correlation was found between serum selenium levels and height-for-age (r=−0.159). In fact, selenium deficiency has been reported as one of the major health problems in Gondar, Ethiopia [31
], as in Asia and Africa [62
]. Deficiencies of selenium contribute to the prevalence and severity of iodine deficiency disorders which are the most important and well-known global nutritional problems, primarily in developing countries [18
]. Selenium is an integral part of the enzyme glutathione peroxidase, which forms a major cellular defense system against oxidative injury [13
]. Selenium deficiency has been incriminated in the causation of several diseases including malignancies [13
]. The diversity of nourishment sources, regional variation and different ethnic diets makes it difficult to extend these results to the whole population; however, it appears that more work is required to define acceptable requirements for selenium and zinc intakes, the prevalence of their deficiencies, and their public health significance.
Serum molybdenum level in this study was higher among school children and its level was positively correlated to height-for-age (r=0.275, p
<0.01). However, mean serum molybdenum concentrations did not differ significantly between different nutritional statuses. In human and animal tissues, the enzymes xanthine dehydrogenase (XD)/oxidase (XO), aldehyde oxidase (AO) and sulfite oxidase (SO) require molybdopterin as cofactor and part of the enzyme molecule [64
]. This is the first study to demonstrate the serum concentration of molybdenum among school children in Ethiopia. More research is required. Without it, the public health significance of serum molybdenum concentration in Ethiopia children and adults will remain uncertain.
It is well known that the relationship between malnutrition and infection is an intimate one, and it is often understood that this is because of impaired immune function. In the present study, we did a stool examinations and the overall prevalence of intestinal parasitic infections amongst the school children was 18%, which is low compared to different studies conducted in different parts of Ethiopia (35.5% and 83.8%) [66
]; the difference may be due to the fact that infection rates depend on factors such as local personal hygienic and sanitary conditions, ecology and geography, among other factors. This decline can also be attributed to the conduct of mass deworming programmes targeting under five children in many parts of Ethiopia as a component of the Enhanced Outreach Strategy (EOS) started in 2004 [68
]. It is therefore suggested that intervention measures have to be strengthened to further reduce intestinal helminthic infection among children and the community. This may include: improving sanitation and personal hygiene through continuous health education, multi-micronutrient supplementation, mass deworming and periodic treatment of the children.
Finally, as summarized in Table , results of serum levels of magnesium, calcium, iron, copper, zinc, selenium and molybdenum among children in this study and those reported from different countries has been presented. The levels of serum magnesium, calcium, iron, copper and zinc were higher in this report than reports from other countries [19
]. The average selenium level in the current study participants (6.32±2.59 μg/dl) is lower to their Iranian counterparts (7.21±1.68) [26
Comparison of the mean serum levels of micronutrients in children from different countries
A limitation of the present study is lack of detailed information on socioeconomic status, and non-availability of data on dietary intake. Such data may provide useful information to explain the situation of micronutrient status and deficiency in the population studied.
In summary, this study shows that the serum concentration of micronutrients in school children with different nutritional status was altered. The findings of the present study also reveal a high prevalence of zinc and selenium deficiencies, individually as well as concomitantly, among the school children in Gondar. Although prevalence of malnutrition was decreasing in the area [38
], the prevalence of both malnutrition and intestinal parasitism was not negligible in this population. These calls for the need to undertake multicentre studies in various parts of the country to substantiate the data obtained in the present study so that appropriate and beneficial strategies for micronutrient supplementation can be planned.