Nutrition literacy across adolescence stages in Egypt: a quartile-based analysis for tailored educational strategies | BMC Public Health

Study design and target groups

A cross-sectional study was conducted across Egypt’s distinct geographical and socioeconomic regions from January to September 2022. The study targeted adolescents of both genders, aged 10–19 years, who consented to participate. The participants were categorized according to the World Health Organization (WHO) criteria for the stages of adolescence [40], early adolescence (10–13 years), middle adolescence (14–16 years), and late adolescence (17–19 years). The study aimed to assess the nutritional literacy of adolescents across these age groups.

Sample size calculation and selection

The sample size was calculated based on an estimated proportion of 18.1% for adolescents with inadequate total nutrition literacy (TNL) in each adolescence stage. A sample size of 297 provided a two-sided 97% confidence interval with a margin of error of 0.100. The sample size was calculated as follows [41].

Numeric results for Two-Sided confidence intervals for one proportion

Confidence interval formula: exact (Clopper-Pearson)

To ensure representation across the three stages of adolescence and socioeconomic strata, the sample size was increased to 1,050 participants, with 350 adolescents from each age group (early, middle, and late adolescence) [42]. By focusing on adolescents, the study captures a critical period of development during which nutrition literacy can significantly impact both immediate and long-term health outcomes.

Study setting and participant selection

Participants were recruited from households through a multi-stage random sampling approach. Stage one was the selection of governorates to represent the main districts of four Egyptian regions. each governorate represented distinct geographical and dietary regions of Egypt: Cairo (representative of the Greater Cairo region representing Urban/metropolitan region); Fayoum (representative of Upper Egypt representing Agricultural region); Al Dakhlyia (representative of the Delta region) and Marsa Matrouh (representative of a border/frontier governorate). Each region has unique dietary habits and crops, contributing to the study’s focus on the diversity of dietary patterns across Egypt. These governorates were randomly chosen to capture various dietary practices, socioeconomic backgrounds, and cultural influences on nutrition. This selection enhances the study’s relevance to Egypt’s broader context [43, 44]. Cairo is a dense urban setting with high dietary diversity, while Fayoum and Al Dakhlyia represent agricultural areas with traditional dietary practices, and Marsa Matrouh, a frontier region, has limited food access compared to other areas.

For each governorate, both urban and rural areas were targeted for addressing the regional variability in nutrition literacy. By including both urban and rural households in each governorate, this study accounts for these disparities, enhancing the generalizability of the findings. During phase three, participants were stratified by socioeconomic status (SES) using the Economic Research Forum and CAPMAS (Central Agency for Public Mobilization and Statistics) wealth index (low, middle, and high). To minimize selection bias, random sampling was conducted in urban and rural districts within each SES group, with three cities and three local village units chosen per stratum. This structured approach also addresses potential oversampling biases in urbanized areas, ensuring that rural adolescent voices are represented adequately [45]. This selection was designed as part of a broader effort to identify children at high risk for autism, and it adhered to the study’s inclusion and exclusion criteria [46]. Adolescents were randomly selected through a community house-to-house approach.

For each targeted governorate, 45 participants (15 per adolescent stage) were recruited from each social class, resulting in a total of 225 adolescents from each governorate, with the exception of the Cairo governorate, which had 270 participants (90 per each social class, 30 per each adolescent stage).

Inclusion criteria

The study included adolescents aged 10–19 years, classified according to the World Health Organization (WHO) adolescence stages, encompassing early, middle, and late adolescence. Both male and female participants were eligible, provided they had been residing in the selected governorates for at least one year to ensure their dietary habits reflected the local environment. To account for variations in educational background, the study included adolescents actively attending school in public, private, or community-based educational institutions, as well as those who had dropped out of school but had completed at least six years of formal education, ensuring they possessed the necessary literacy skills to engage with the study materials. Additionally, informed parental consent and adolescent assent were mandatory for participation.

Exclusion criteria

Adolescents were excluded from the study if they had diagnosed cognitive impairments or severe learning disabilities that could hinder their ability to complete the nutrition literacy assessment. Those who had not completed at least six years of formal education were also excluded, as they might lack the foundational literacy skills required for the questionnaire To minimize confounding factors, adolescents with chronic medical conditions affecting nutrition intake, such as diagnosed eating disorders or metabolic disorders, were excluded unless their condition was a specific focus of the study. Additionally, non-Egyptian adolescents or those who had moved to Egypt within the past year were not included, as their dietary habits and environmental influences might not align with the local context. To prevent potential clustering biases within families, only one adolescent per household was selected for participation.

Data collection instruments and procedures

Questionnaire administration

A self-administered questionnaire was utilized to gather data from the adolescent participants. This questionnaire was filled out under the guidance of the research team to ensure clarity and accuracy. The questionnaire was adapted from a previously validated tool, originally designed and published by Hoteit and colleagues [47], ensuring its relevance to the adolescent population in the context of nutrition literacy (NL) assessment. A pilot study involving 10% of the participants was conducted before the main study to enhance clarity, minimize ambiguity, and address potential sources of measurement error.

The questionnaire was divided into two major sections:

Demographic and socioeconomic information

This section focused on collecting essential background information on the enrolled adolescents. The demographic variables collected included the participants’ age, gender, educational level, and details on their primary caregiver (i.e., who was primarily responsible for their daily care). Additionally, the study gathered data on the education levels of both parents, as parental education often influences the nutritional habits and literacy of children. Household Crowding Index: Calculated as the number of co-residents (excluding newborns) divided by the number of rooms (excluding kitchens and bathrooms [48,49,50].

Parents provided self-reported anthropometric data (weight and height) to calculate Body Mass Index (BMI), facilitating assessment of nutritional status in line with WHO’s BMI-for-age guidelines. Participants were instructed to provide recent height and weight measurements to reduce potential reporting biases, particularly in anthropometric data. However, the reliance on self-reported anthropometrics remains a limitation, as it introduces the possibility of data inaccuracy, an issue common in large-scale, self-administered surveys Participants also reported on their intake of vitamins and minerals, providing insight into their dietary supplementation habits.

Vitamins assessment

Assessing adolescents’ consumption of dietary supplements focused on participants’ report on vitamins D, C, A, B12, and folic acid intake. Assessment of these particular vitamins was crucial due to the essential roles these micronutrients play during this critical developmental stage. Adolescence is marked by rapid growth and physiological changes, increasing the demand for nutrients that support bone development, immune function, cognitive maturation, and overall health.​ Monitoring supplement intake in this demographic helps identify nutritional gaps and informs interventions aimed at promoting balanced diets rich in essential vitamins.

Vitamin D

is vital for calcium absorption and bone mineralization, processes that are foundational during the adolescent growth spurt. Adequate vitamin D levels are necessary to achieve optimal bone density, reducing the risk of osteoporosis and fractures later in life [51].​.

Vitamin C

serves as a potent antioxidant and is essential for collagen synthesis, which is integral to the structural integrity of skin, blood vessels, and connective tissues. It also enhances immune defense mechanisms, aiding in the prevention and recovery from infections [52, 53].​.

Vitamin A

is crucial for vision, immune competence, and cellular differentiation. During adolescence, sufficient vitamin A intake supports the development of epithelial tissues and bolsters the body’s ability to combat pathogens [54].

Vitamin B12

is indispensable for neurological function and the formation of red blood cells. Its role in DNA synthesis and myelination of nerve fibers is particularly pertinent during adolescence, a period characterized by significant cognitive and physical development [55].​.

Folic acid (vitamin B9)

is essential for DNA synthesis and repair, supporting rapid cell division and growth. Adequate folic acid intake is vital during adolescence to prevent megaloblastic anemia and to support neural development [56].

Minerals assessment

Understanding which supplements adolescents consume provides insights into existing nutrient gaps and overall dietary patterns. Dietary supplements, such as multivitamin/mineral products, have been shown to help fill nutrient gaps and improve micronutrient sufficiency among children and adolescents. However, there is a concern about the over-reliance on supplements as substitutes for whole foods, which can lead to lower overall energy intake and lack of consumption of other critical nutrients found in whole foods [57, 58]. The current study focused on participants’ report on consumption of dietary supplements, specifically calcium, magnesium, iron, and zinc, that is grounded in their critical role in growth, development, and overall health during this life stage [59]. Adolescence is a period of rapid skeletal growth and bone mineralization, making calcium and magnesium essential for maintaining strong bones and preventing future conditions like osteoporosis and fractures. Since bone mass peaks during adolescence, ensuring adequate intake of these minerals is crucial for long-term musculoskeletal health [60, 61].

Beyond skeletal development, iron and zinc are fundamental for cognitive function, immune health, and metabolic processes. Iron deficiency is a leading cause of anemia among adolescents, particularly in females due to increased iron loss from menstruation, which can lead to fatigue, decreased concentration, and poor academic performance [62]. Similarly, zinc plays a key role in immune function, wound healing, and enzymatic reactions, helping adolescents maintain overall health and fight infections during a stage of high physiological demand [63].

In this study, data on vitamin and mineral intake reflect self-reported use of dietary supplements only, specifically including calcium, magnesium, iron, zinc, and multivitamin preparations. These data do not include intake from food sources. Dietary intake of vitamins and minerals from regular meals was assessed as part of a broader project; however, those findings are presented in a separate manuscript.

Nutrition literacy and food literacy assessment

The second part of the questionnaire measured the nutrition literacy (NL) of the adolescents and the food literacy of their parents. Nutrition literacy refers to the ability to obtain, process, and understand basic nutrition information needed to make appropriate health decisions.

To assess NL, the Adolescent Nutrition Literacy Scale (ANLS) developed by Bari [64], was utilized. This comprehensive tool consists of 22 questions, categorized into three distinct components:

• Functional Nutrition Literacy (FNL): This component, composed of 7 questionsassessing basic nutritional information comprehension. It evaluated the adolescents’ ability to comprehend and use basic nutritional information, such as their understanding of nutrition-related scientific terms, dietary guidelines, and the recommendations provided by public health professionals. For instance, it included questions assessing participants’ familiarity with international dietary guidelines, such as those from the World Health Organization (WHO) regarding fruit and vegetable intake. The scoring range for FNL is 7–35, with a cut off score of ≥ 21 indicating adequate functional literacy.

• Interactive Nutrition Literacy (INL): The 6 questionsin this component measured the adolescents’ skills in seeking out, discussing, and applying nutrition-related informationwithin social contexts, including communication with peers, family members, and health professionals. The ability to engage with nutrition topics and translate this knowledge into practical actions, such as modifying dietary habits based on newly acquired information, was a key aspect of this component. The score for INL ranges from 6 to 30, with a cut off score of ≥ 18 considered adequate.

• Critical Nutrition Literacy (CNL): The9 questionsin this section focused on the adolescents’ ability to critically assess nutrition information and influenceothers’ dietary practices. It assessed participants’ engagement in activities that promote healthy eating, support for policies that improve dietary habits, and their ability to evaluate the credibility of nutrition-related information, particularly from social media and other sources. The score range for CNL is 9–45, with a cut off score of ≥ 27 indicative of sufficient critical literacy.

Total nutrition literacy (TNL)

was calculated as the sum of the three components (FNL, INL, CNL), yielding a total possible score between 22 and 110. A cut off score of ≥ 66 reflected adequate overall nutrition literacy. This metric provided a comprehensive view of the adolescents’ ability to understand, interact with, and critically evaluate nutrition information.

To assess parental food literacy, the validated Short Food Literacy Questionnaire (SFLQ) developed by Gréa Krause et al. [65] was used. The parental food literacy questionnaire was composed of 12 questions, divided across three dimensions similar to those assessed in the adolescent scale but with fewer questions per category: Functional food literacy (6 questions); Interactive food literacy (2 questions); Critical food literacy (4 questions).

The parental food literacy score ranged from 7 to 52, with a cut off score of ≥ 36 indicating adequate food literacy. This allowed for comparison between the literacy levels of parents and their children, providing a deeper understanding of family dynamics regarding nutrition knowledge and behaviors.

Nutritional and growth status assessment

In addition to the self-reported data of the parents, a physical assessment of nutritional status was conducted. By conducting in-person measurements, this study enhances data reliability and consistency across rural and urban participants. Additionally, anthropometric data allows for exploring relationships between growth status and nutrition literacy, which could reveal developmental implications of inadequate nutrition literacy during adolescence. Anthropometric measurements of weight and height were taken using standardized equipment and techniques. Weight was measured with a Seca Scale Balance, while height was recorded using a Holtain portable anthropometer. These measurements were critical for evaluating the growth status of the adolescents, as weight and height are primary indicators of nutritional health. The BMI was calculated as weight (in kilograms) divided by height (in meters) squared based on the WHO growth standards with the help of the Anthro-Program of PC [66]. The body mass index (BMI) was evaluated as follows: underweight if BMI is less than 18.5, normal/healthy weight if BMI is 18.5 to 24.9, overweight is BMI is 25.0 to 29.9, and obese if BMI is 30.0 or higher [67]. The BMI classification provided an additional layer of insight into the participants’ nutritional health, correlating with their dietary habits and nutrition literacy levels.

Measures to ensure validity and reliability of tools used for NL and FL assessment

Both ANLS that is developed by Bari [64] and SFLQ that is developed by Gréa Krause et al. [65] have been translated, culturally adapted and utilized in Arabic-speaking contexts. They have been adapted in a study to assess the nutrition literacy of adolescents across countries including Lebanon, Bahrain, Egypt, Jordan, Kuwait, Morocco, Palestine, Qatar, Saudi Arabia, and the United Arab Emirates [68]. The study involved 5,401 adolescent-parent dyads and found that 28% of adolescents had poor nutrition literacy. However, the study did not detail the process of translating or validating the ANLS and SFLQ for each specific Arabic-speaking context and it did not provide specific psychometric properties of the Arabic-translated tools.

We have conducted a multistep process to mitigate this for ensuring the tools appropriateness for our target population. Initially, a pilot test was conducted before large-scale implementation to ensure the clarity and appropriateness of the translated Arabic ANLS and SFLQ tools. This step involved administer of the Arabic versions of the tools for 10% of different participants as a pilot sample (n = 105) to assess their usability and ensure that participants could complete the questionnaire without difficulty. Subsequently, to assess internal consistency, the study employed Cronbach’s alpha [69]. with a larger sample of 330 participants, achieving high values of Cronbach’s alpha (0.89 for ANLS and 0.86 for SFLQ, ≥ 0.8) that indicated strong reliability [70]. To assess the stability of responses over time, a subset of 105 participants completes the Arabic SFLQ twice, with a two-week interval (test-retest reliability). The Intraclass Correlation Coefficient (ICC) was calculated to measure consistency, achieving ICC of 94% and 92% respectively indicating excellent reliability (ICC ≥ 0.75) [71]. This comprehensive approach ensured that the Arabic ANLS and SFLQ are scientifically sound and culturally relevant tool for assessing nutrition literacy among Arabic-speaking adolescents.

Statistical analysis

Data were analyzed using the Statistical Package for Social Sciences (SPSS), version 26. Various statistical techniques were employed to summarize and analyze the collected data: Categorical variables (e.g., gender, social class, nutritional literacy categories) were summarized as numbers and percentages. Continuous variables (e.g., BMI, literacy scores) were presented as means and standard deviations.

Statistical significance was determined using: Pearson’s Chi-square test (χ²) and Fisher’s exact test to assess associations between categorical variables. Z-tests were applied for comparisons of proportions.For comparisons of means between groups, the t-test and ANOVA were utilized. Crude Odds Ratio (COR) with 95% confidence intervals (CI) were calculated to examine associations between adolescence stages and nutritional literacy. Logistic regression analysis was conducted to identify significant predictors of adequate TNL among the adolescents.A p-value < 0.05 was considered statistically significant, indicating a meaningful association or difference, while a p–value < 0.01 was considered highly important, highlighting particularly strong associations or differences.