Data analysis of both studies (expert and student study) was merged into the themes developed at the first study. In both expert and student studies, food and nutrition literacy were found to be highly contextual. The final analysis of data from three sub-studies led to identifying thirteen components, and two main domains of cognitive domain and skill domain are presented in Table 2. More explanations are presented as follows.
Food and nutrition-related knowledge
In the cognitive domain, food and -related knowledge was the first concept that developed during continuous analysis and data comparisons. This concept represents the food and nutrition-related basic knowledge, which was essential for children based on the experts’ view. This concept encompasses four components: food and nutrition knowledge, lifestyle knowledge, food safety knowledge, and the knowledge of food and food preparation. One of the nutrition experts of UNICEF described: “The students of 5th and 6th grade are expected to be aware and understand basic food and nutrition information to make decisions to improve their nutritional and know how proper diet and nutrition play a role in preventing obesity.”
Most experts considered that having an overall concept of nutrition basics and the balance of foods was more important than more detailed information for this age group. A nutrition expert of Ministry of Health and Medical Education argued: “In my opinion, a student of 5th and 6th grade should be aware of nutrition basics, that is he/she should know about food groups and their nutrition value, and he/she should be familiar with varied, well-balanced diet, the students should know what meals are and why and how they should eat meals; what are healthy snacks and why they should eat them….”.
Understanding food and nutrition information
Most experts believe that food and nutrition literacy means that students have the capacity to apply food and nutrition information to the health situation, which requires understanding and interpreting the often-complex information about food and nutrition.
According to students’ views, lack of food and nutrition information in plain and understandable language was a significant barrier to using this information. “Sometimes I don’t understand the nutrition information so, I ask from my teacher but sometimes he cannot explain things to me in plain or even in terms I know.”(A student in grade 5).
Functional food and nutrition literacy
According to experts’ views, the ability to seek and identify reliable sources of nutritional information is one of the key required skills. Interviews indicated that most children asked their questions about food and nutrition information from parents, teachers and searched on the internet.
Nutritionists stated that in addition to the ability to seek required food and nutrition information, students should apply this information in their lifelong eating behaviors. This concept can be considered both a component and a potential outcome of food and nutrition literacy using both studies. In relation to food choice skills, one of the students said, “when I want to buy something, I check production and expiration date and standard sign. I also check its ingredients”. (A student in grade 5)
Some of the students mentioned their skills in preparation some food such as; “Scrambled egg, Macaroni, Omelette and Cutlet….” (A student in grade 6).
Interactive food and nutrition literacy
According to experts’ views, enhanced confidence contributed to new ways of communicating about food and nutrition issues with peers, friends, and children, highlighting the social aspects of food and nutrition literacy. A nutritionist from a research site stated that” one should share food and nutrition information with others because in interactive literacy we would like individuals to apply the food and nutrition information in their relationships. This relation may be with a nutritionist, teacher, parents, and peer and…”
The ability to withstand cravings and non-nutritious foods and the skill of saying “No” to unhealthy eating temptations that two of the nutritionists in the Ministry of Health and one of the nutritionists from the education system referred to conceptualized as emotional skill included in interactive food and nutrition literacy skills.
Among the participants’ statements, the ability to argue and disagree with the non-nutritional behavior of peers and the family was one of the skills that were included in this domain.
“One of the other skills is that if the family were unhealthy in their food behavior, then the person could convince them or be able to independently manage own diet.” (A nutritionist from education system)
Critical food and nutrition literacy
The main identified components in this dimension were media literacy, food label literacy, and decision-making and planning skill.
One of the concepts in the process of continuous data analysis was media literacy. Today, we live in an advertisement-saturated world where consumption of unhealthy food and fostering unhealthy eating habits are promoted. Children as loyal and persistent customers of food marketing are exposed to and deceived by these misleading advertisements. According to experts in our study, developing media literacy in children is an essential skill that empowers them to evaluate and respond to media advertisements. In our study, most students did not trust the advertisements, and some of them believed they should investigate the trustworthiness of the advertisements. A student in grade 5 said: “Advertisements are not true, and most of them are wrong and sell their products. I saw a fruit juice advertisement saying that fruit juice is made from real juice, but when I bought it and read its ingredients, it consisted of water, sugar, and flavors.”
Food label literacy
In the expert study, participants referred to the importance of food labeling. They believed it was one of the best ways to transmit nutritional messages at the point of purchase. One of the nutritionists in the Ministry of Health, while pointing out the initiation of mandatory traffic lights, stated that “traffic lights are the first and most important guide in which the consumer can communicate with food products through color markers. Traffic light may be more practical for children because of their simplicity.”
Decision-making and planning skills in special condition
Managing money and time for preparing healthy food, healthy decision making in particular circumstances, and the ability to plan for own health, others, and the surrounding environment, were the components referred by participants. This component helps the individual minimize the impact of restricted resources or other special situations on healthy food choices.
A total of twenty-nine studies were included in the final review. Of these, 21 studies simultaneously addressed both food/nutrition literacy definitions and its components [5,6,7,8, 28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44], three studies only defined food/nutrition literacy [45,46,47] and 8 focused on food/nutrition literacy conceptual framework and its components [7, 8, 30, 31, 36, 38, 47, 48] in youth and adults. The main elements of all conceptual frameworks of food literacy included nutrition basic knowledge, and skills required to regulate food intake, planning meals, selecting and preparing food. Only three conceptual frameworks of food literacy comprised skills such as sharing information and interacting with others [7, 36, 38, 39]. All definitions of nutrition literacy and half of the food literacy definitions were based on an existing definition of health literacy [6, 7, 31, 36, 38]. The most emphasized components in “food literacy” were food skills including management, food preparation, and food selection as well as critical literacy [7, 38, 49, 50]. Slater (2013) presented food literacy using Nutbeam’s idea of health literacy as a framework for the food and nutrition curriculum of schools . Based on the literature, all definitions of nutrition literacy focused on individuals’ cognitive abilities and strongly emphasized fundamental literacy and numeracy abilities required to comprehend and utilise nutrition-related information (functional skills). However, none provided a conceptual framework for nutrition literacy. For a general overview, see additional file 2.