Background
Undernutrition poses a serious challenge in developing countries [
1]. The World Health Report of 2016 estimated that about 155 million children under five years of age are stunted and 52 million wasted [
2]. The rates of undernutrition were substantially higher in the Sub-Saharan African (SSA) region [
1,
3]. In Tanzania, a high prevalence of chronic and acute undernutrition still persists. It was estimated that about 450,000 children in Tanzania are acutely undernourished or wasted, with over 100,000 suffering from the most severe form of acute malnutrition [
4], making it a country with one of the highest undernutrition burdens in Eastern and Southern Africa [
5]. The recently released national survey of 2018 reported that 31.8% of children were stunted, 3.6% were wasted and 14% were underweight [
6]. The damage caused by undernutrition during the first two years of life may compromise cognitive development of the children and in turn result in poor educational achievement, low economic productivity, and is associated with illness and mortality during adulthood [
7].
Poor infant and young child feeding practices are the main causes of undernutrition in Tanzania [
8,
9] and other developing countries [
2]. From the age of 6 months, breastfeeding is no longer able to meet all nutritional requirements of a growing child, and therefore, the consumption of adequate, diversified food is necessary [
10,
11]. Globally, however, only less than one-fourth of infants aged 6–23 months meet the recommended criteria for dietary diversity, and only a few of them are receiving a nutritionally adequate diet [
2]. The World Health Organization has recommended that an infant should receive the minimum dietary diversity (MDD) of at least four food groups out of seven in order to maintain proper growth and development during this critical period [
12], but many children cannot meet these criteria. In Tanzania for example, according to the recent report, only 35.1% of children aged 6 to 23 months had received the MDD [
13], and only 23.3% in Ethiopia [
14]. Dietary diversity, as a marker of micronutrient adequacy, may increase nutrient density of the complementary foods [
15], which promote optimal child growth and development. Receiving an inadequately diversified diet may lead to undernutrition [
16], and predispose children to opportunistic infections and severe illnesses [
7].
Although the association between dietary diversity and the nutritional status of children has already been studied in various countries [
16‐
21], studies that use large-scale data are scarce, particularly in Tanzania. In addition, many previous studies in Tanzania have largely focused on other aspects of child nutrition, like micronutrient content [
9], complementary feeding practices [
9,
22‐
25] and their determinants [
26,
27]. None of them, according to our literature review, has examined the association between child diet diversity and nutritional status. Understanding the influence of dietary diversity on the nutritional status of children could be useful to inform nutrition policy and propose interventions that focus on improving the quality of complementary foods. Findings from this study will therefore be important to public health experts in Tanzania and help to work towards the Sustainable Development Goal-2 (SDG-2) agenda, which aims to end malnutrition in all its forms by 2030 [
28]. The present study examined the role of child dietary diversity on undernutrition in Tanzania by using the large available dataset, which is representative of the whole country.
Discussion
This study aimed to examine the association between dietary diversity and undernutrition of children aged 6 to 23 months in Tanzania. In this study, dietary diversity was found to be a protective factor against stunting (HAZ) and underweight (WAZ) among children in Tanzania. These results are consistent with findings reported from other developing countries like Burkina Faso [
19], Bangladesh [
30], Ethiopia [
18], and others [
16,
21]. Our study suggests that undernutrition can be reduced by improving the dietary diversity of complementary foods in Tanzania. This is supported by the fact that dietary diversity is a good predictor of dietary quality and micronutrient density in children [
15,
31]. Therefore, generally, this makes dietary diversity one of the important factors that policy makers should adopt to improve the nutritional status of children in the country.
However, this study did not find an association between wasting and the dietary diversity of children using the MDD indicator. This is in line with findings from other studies [
19,
32]. As a previous study from Ethiopia has shown, wasting is more likely to be associated with diseases or household food insecurity rather than dietary diversity [
18]. This might be due to the fact that wasting refers to acute malnutrition as a result of shorter-term episodes of inadequate feeding or illnesses [
33].
Our study shows that only a small proportion (26%) of children of 6 to 23 months old in Tanzania reached the MDD. This is identical to a finding by Ochieng et al. who looked at factors affecting household nutrition security in Tanzania, which reported that only 26% of children had reached the MDD [
27]. Overall, the present study shows that consumption of animal-source foods like meat, milk and eggs is not very common among children of 6–23 months in Tanzania. Similarly, the study by Ochieng et al. reported that meat and fish were consumed by less than 10% of children under five years [
27]. These outcomes are not surprising considering the seasonal and geographical unavailability of some foods, the restrictions imposed by traditions, and possible financial constraints in Tanzania [
34]. In this study, children who did not consume any meat were more likely to become stunted. This result corresponds with a survey of 12 to 59 month old children in Cambodia, which concluded that the consumption of animal-source foods was a protective factor against stunting and underweight [
17]. Animal-source foods like meat, milk, eggs and poultry have a variety of micronutrients including vitamin A, vitamin B-12, riboflavin, calcium, iron and zinc that are difficult to obtain in adequate quantities from plant sourced foods alone [
35]. Thus, insufficient intake of these nutrients may hinder the physical development of a child, resulting in stunting [
2]. We therefore highly recommend that public health officials should educate parents and caregivers on the importance of animal-source foods for their children.
Moreover, our analysis emphasizes that the consumption of milk and dairy products is very beneficial for growing children. We found that non-consumption of milk products is a predictor of stunting among children. Failure to give any milk or dairy product at this critical age may result in protein imbalance [
2]. Milk is one of the basic foods which can easily provide adequate nutrition when consumed regularly in relative small quantities and which can promote a child’s health and is available throughout the year [
36]. Therefore, health education messages related to the importance of milk and dairy products as complementary foods is a critical public-health intervention in Tanzania.
Another interesting finding in this study was the association of vitamin A fruits and vegetables with underweight among children. In this study, children who did not consume vitamin A containing fruits and vegetables were more likely to become underweight. Similar findings were reported from a study among children in Ghana [
21]. Also, previous research has shown a significant association between Vitamin A intake and undernutrition, but not among infants [
37]. Vitamin A is known as an essential micronutrient for growth and immunity. Its deficiency is one of the most important causes of preventable childhood blindness and is a major contributor to morbidity and mortality from infections [
37]. Therefore, based on these findings, lack of adequate vitamin A intake may results in the increase of underweight children in the country. It is therefore important for mothers to increase the inclusion of foods rich in vitamin A such as spinach, mangoes and papaya as complementary foods given to their children. These foods are relatively cheap in Tanzania and are easily accessible in both rural and urban areas for most of the year.
We also found that, children who did not consume any food made from grains or legumes were more likely to become wasted. In many countries, including Tanzania, grains and cereals including maize, sorghum, millet and rice are among the first foods that are introduced at the beginning of the complementary feeding period to infants [
9,
22,
23,
38]. These are very beneficial for the children because they are an excellent source of energy, vitamins and minerals [
38]. Therefore, to reduce the prevalence of undernutrition, mothers should provide adequate foods that provide adequate energy and all nutrients to their children.
However, it is important to mention some important limitation of this study. We only considered the dietary diversity as indicator of the overall quality of the child’s diet. This study did not take into account the quantity of the foods consumed, and is therefore not able to reliably predict that foods consumed met the required dietary intake. Also, due to the cross-sectional nature of this study, a cause and effect relationship cannot be assured and we have to interpret our findings with caution. Additionally, some indicators of the nutrition status like stunting represent a long-term cumulative process, whereas the dietary information available in the TDHS reflects only the previous day before the survey. In addition, the responses given by mothers/caregivers are sometime based on their ability to recall types of foods and their desire to please the surveyor. In spite of the mentioned limitations however, this present study can shed light on how dietary diversity is likely to influence the development of undernutrition in Tanzania. Future, large scale studies are needed to identify the causal relationship between diet and the physical and mental condition of the children in Tanzania.
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