1. Introduction
Malnutrition among school-aged children in Uganda remains high [
1,
2] as 22%–38% are considered stunted, 38% are anaemic, and 80% are iron-deficient, undermining national education efforts. This is partly due to poor feeding practices at homes and at schools [
3]. Approximately 40% of the schools do not provide meals; 92% of rural children go to school without breakfast and 70% do not eat lunch at school. Additionally, few schools provide fruits, vegetables, animal source, and fortified food that can reduce micronutrient deficiencies [
3]. Poor nutrition status manifests from the complex interaction of biological, intra- and interpersonal, and environmental factors that determine food choices and consumption among children [
4]. At schools, head teachers’ actions are among the many interpersonal factors that can influence the school environment for children and, potentially, for their parents and other teachers. Head teachers are centrally positioned to promote nutrition in schools and their communities, often supporting nutrition interventions led by government and development partners [
5,
6]. Nonetheless, the ability of teachers and heads to influence healthy behaviours at schools might be limited by their knowledge of and attitudes towards nutrition [
7].
The determinants of diet-related behaviours include biologically determined behavioural predispositions, experience with foods (physiological and social conditioning), intra- and interpersonal factors, and environmental factors [
4]. Knowledge is a key determinant of behaviour, categorized within inter- and intrapersonal factors [
4] and included within several theoretical frameworks such as the Social Ecological Model and the Social Cognitive Theory [
8,
9,
10,
11]. Increased nutrition knowledge has been associated with improved dietary habits and lower rates of obesity [
12,
13,
14]. Furthermore, prior evidence indicates that gender differences in nutrition knowledge may explain differences in unhealthy behaviours, such overeating and smoking habits [
15,
16]. These studies suggest that monitoring and evaluating nutrition knowledge using valid instruments is an important component of health and nutrition education.
In Uganda, most studies have focused on evaluating knowledge, attitudes, and practices associated with nutrition in vulnerable populations, e.g., people with HIV-AIDS, infants, and young children [
17,
18]. These studies, however, have inadequately evaluated nutrition knowledge. The issue stems from two major factors; disagreement on a definition of nutrition knowledge and the use of instruments that are not validated [
17,
18]. Nutrition knowledge is defined as the understanding of basic facts about food and nutrition [
19,
20,
21,
22]. At a very basic level, nutrition knowledge should be defined by at least two of the following concepts during evaluation; food groups, balanced diets, current dietary guidelines, sources of nutrients, storage and preparation of food, use of food labels, and the relationship between nutrition and disease [
19,
20,
21,
22,
23,
24]. Most studies evaluating indicators of nutrition, including knowledge, in Uganda often adapt questionnaires from elsewhere, which do not undergo the complete validation process [
17,
18]. The lack of validated instruments negatively affects the quality of the resulting data and its extrapolation to a wider population, as well as limiting the ability to compare results from different studies [
25]. Additionally, not validating survey tools reduces the ability of any given study to detect associations with other modulating factors, specifically feeding behaviors [
25]. As a result, the use of low-quality data could negatively impact policies and programs and the effective use of resources. In Uganda, this was identified as a major gap to scaling up public nutrition action [
26].
In order to support future nutrition education interventions in Uganda, this study sought to validate a general nutrition knowledge questionnaire (GNKQ) for adults using a systematic approach, involving college students and head teachers.
4. Discussion
Currently, there is no valid tool to collect general nutrition knowledge in Uganda or the great majority of countries in Sub-Saharan Africa. The initial GNKQ (133 items) was reviewed to include commonly consumed food items in Uganda [
34,
35], the concept of ‘food fortification,’ and current nutrition-related guidelines and policies in Uganda (
Table 2) [
26,
48,
49]. Five experts in nutrition-related disciplines reviewed the first GNKQ drafts resulting in high consensus on the relevance of constructs (CVI and Gwet’s AC1 > 0.96). Previous studies have used at least three experts to review similar questionnaires aimed at evaluating the nutrition knowledge of adults [
19,
20,
27,
28,
29,
30,
31]. None of these studies, however, reported the level of agreement among experts on the relevance of the contents of the different constructs of the GNKQs. The content validity index (CVI) is a one proportion agreement method that has been used in the past to quantitatively estimate content validity [
40,
44]. Experts in survey evaluation suggest reporting at least two measures of agreement [
40,
50,
51,
52]. Relying on only CVI is not adequate because it might inflate agreement among experts since there is no adjustment for chance agreement [
50]. Gwet’s AC1 was used as a second measure of agreement because of the small sample size of experts and stability concerns of the Kappa statistic. Gwet’s AC1 is a more stable measure of interrater agreement reliability than the commonly used kappa statistic [
42]. The recommended minimum item-CVI is 0.8, while the scale-CVI is 0.9, when using a panel of five or more experts. In the case that less than five experts review the questionnaire, there should be a perfect agreement, i.e., a CVI of 1.0 [
40,
44]. A Gwet’s AC1 above 0.4 represents intermediate to excellent agreement reliability [
42]. Therefore, the GNKQ for Uganda had adequate content validity.
The results from overall internal consistency, test-retest reliability, and construct validity of the questionnaire before and after the deletion of items based on item difficulty and discrimination were adequate and comparable to other studies [
19,
27,
28,
32,
46]. Results from the validation of a similar questionnaire for adults (
n = 125 college students) in Turkey [
27] yielded poor internal consistency for knowledge on ‘dietary recommendations’ (α = 0.47) and ‘choosing foods’ (α = 0.43). These results are comparable to those in this study after the first round of validation with students. Similar to previous studies [
19,
27,
28,
32,
46], the internal consistency (α > 0.7) and test-retest reliability (
r > 0.7) were adequate for three domains of nutrition knowledge i.e., sources of nutrients, food selection, and diet and disease relationship. The poor results on ‘expert recommendations’ may be due to discordant interpretations of nutrition messages partly attributed to limited nutrition education promotion and a lack of unified dietary guidelines in Uganda [
24]. Low internal consistency has also been attributed to the heterogeneity of populations with a varied education background [
22,
34]. The current study included teachers and students with different education backgrounds. Administering the GNKQ to a larger homogenous sample (e.g., head teachers only) could improve these findings on internal consistency. All versions of the GNKQ validated in different countries showed good construct validity [
19,
27,
28,
32,
46]. Similar to these studies, nutrition students scored higher than engineering students on the overall score and in each topic, demonstrating that the GNKQ has adequate construct validity.
Even though results obtained in this study support the validity of the questionnaire to evaluate the nutrition knowledge of adults, there are some limitations. In this study, the focus was on developing a nutrition knowledge questionnaire for adults with the ultimate goal to evaluate nutrition knowledge among head teachers, as they are often recruited in the implementation of government nutrition policies. The educational attainment of head teachers is higher than most of the low-income population in Uganda, which requires further adaptation of the GNKQ for populations with limited education. In addition, the GNKQ mainly evaluates declarative rather than procedural knowledge. The questionnaire, however, could be used as a first step in the evaluation of attitudes and behaviors toward nutrition. Although very common in the literature, the use of students to evaluate construct validity may not be appropriate to establish this attribute in a more diverse adult population.
The development of instruments to collect valid and reliable data is critical for both scientists and practitioners, particularly in Sub-Saharan Africa. The items in the revised GNKQ draft had good validity and reliability in a sample obtained from Kampala district. Kampala is represented by diverse population groups including urban, peri-urban, rural, agricultural, cultural groups, the affluent, and the poor. This diversity potentiates the ability of the GNKQ to obtain valid results when used in other regions. Potentially, the questionnaire can be used to collect information on nutrition knowledge and its change after interventions among various population groups, especially opinion leaders or influential agents such as teachers, agriculture extension agents, and health workers. Moreover, the adaptability of the questionnaire can be evaluated in other countries in Sub-Saharan Africa.