The results of the present study showed that the mean score in none of the FNL domains and dimensions was above the adequate level (≥60), indicating that the FNL status of Iranian youth needs to be improved. Considering that the study participants were high school students who had completed their formal education, their FNL status conveys key messages for the education system and may reflect the weaknesses of current school curricula in improving food literacy and nutritional issues in students.
There were no significant differences between boys ‘and girls’ scores in the overall FNL and its dimensions, except for scores for functional skills and food label reading. The mean functional skills score was slightly higher for girls than for boys; however, after adjusting for other factors in the multivariate analysis, gender was no longer a significant predictor of functional skills. On the other hand, when it came to food label reading skills, gender was a strong predictor even after adjusting for the effect of all other possible predictors in the multivariate analysis. The results showed that the boys had higher scores in reading and interpreting food labels. A review of the available literature indicates that there is no consistent gender difference in the use of food labels or in interpretation skills. Some studies have shown no difference between the sexes [24,25,26], while some indicated that women used or interpreted food labels more frequently than men [27,28,29]. According to the literature, women seem to use food labels more frequently than men [25, 27, 28]; however, there are inconsistencies between studies regarding the interpretation and understanding of food labels. [24,25,26, 29], suggesting that other factors such as age, level of education, nutritional knowledge, etc., may affect gender differences.
Based on bivariate analysis, maternal education level, private school education, and higher SES score were significantly associated with higher food and nutrition knowledge score. Multivariate analysis confirmed these results; because increasing the SSE score was associated with a higher likelihood of a higher knowledge score. Consistent results have been reported in several studies [12, 30,31,32,33]. Aihara et al. indicated that a higher level of education and economic status was associated with adequate nutritional literacy among the Japanese elderly . Although they used the term “nutritional literacy”, their questionnaire only assessed nutritional knowledge. Likewise, other studies have shown a higher level of education [12, 31,32,33] and workstation [12, 31, 32] were positively associated with nutritional knowledge. The need for food and nutritional knowledge as a prerequisite for dietary changes , although this is not sufficient, calls for the need to put more emphasis on nutrition education programs targeting groups with low SES.
Academic performance was also associated with a higher knowledge score, but surprisingly with lower functional and interactive scores. This may be due to the fact that the country’s current secondary school curricula and textbooks contain relatively little information on food and nutrition, which mainly focuses on knowledge aspects. . In addition, students who perform better in school due to a heavy schoolwork load may have limited time or interest in developing their food and nutrition skills, i.e. doing the exercises. shopping, preparation and cooking (functional skills) or interacting with others about food and nutrition (skills). This may be particularly relevant for our study participants who were high school students preparing for the college entrance exam. More research is needed to draw a more reliable conclusion in this regard.
The possibility of a higher knowledge score was significantly higher among students who studied natural sciences compared to those whose major was literature and humanities. Food and nutrition related topics are more likely to be covered in natural science lessons than in other subjects. A recent analysis of the content of secondary school textbooks in Iran showed that topics related to food and nutrition were covered more frequently in natural science textbooks than other major subjects.  which confirmed the results of the present study.
Subjects’ weight and health status were also examined as possible determinants of FNL and its dimensions. A higher BMI was correlated with a higher functional score on bivariate analysis. However, after controlling for the effect of other possible predictors in multivariate analysis, this association was no longer significant. The relationship between weight status and FNL has been discussed in a number of studies [12, 15, 20, 30, 34, 35]; however, the results have not been consistent. In some studies, people with a higher BMI had a lower FNL level [20, 34], while in others not significant [12, 15, 30] or positive  an association between BMI and FNL has been reported. These surveys were conducted among different age and sex groups, which may partly explain this inconsistency in the results. In a study by Kubiet et al. in adolescents , multivariate analysis showed no significant association between weight status and FNL, which is consistent with our results. However, the limited number of studies, all with a cross-sectional design, makes it difficult to draw a conclusion.
In the present study, the presence of nutrition-related illnesses in a family member predicted the possibility of improved ability to read food labels in students. Previous reports have also indicated that people with nutrition-related illnesses, such as hypertension, diabetes, cardiovascular disease, etc., pay more attention to food labels. . People with chronic nutrition-related illnesses and their families are more concerned with diet and may want to limit the intake of certain specific food components like calories, sugar, fat, salt, etc. These concerns may explain the higher skills in interpreting food labels in people with chronic nutrition-related illnesses. chronic diseases and their families.
To our knowledge, this is the first study to assess the FNL status of Iranian high school students by a valid multidimensional tool. However, this study had certain limitations which must be taken into account. First, its transversal conception makes it impossible to interpret the management of associations. In addition, the determining factors examined in the present study could not explain well the variation in the score of the competence domain and its dimensions. It appears that more complex factors affect FNL-related skills that were not included in our study. For example, food skills may be affected by socio-cultural norms that were not assessed in this study. Therefore, in order to explore the possible determinants of the FNL competence domain, further research, especially with a qualitative design, could provide more information. Finally, this study conducted among high school students in Tehran; therefore, its results may not be generalized to other age groups or different populations.
In conclusion, the present study showed that Iranian high school students have relatively low knowledge and skills in food and nutrition. Among the possible determinants examined, study major, academic performance, and SES were important predictors of young people’s food and nutrition knowledge; and male gender and having nutrition-related illnesses in family members were determinants of improved ability to read food labels. Further studies are recommended to identify other possible factors related to FNL in young people. The findings again highlight the need to assess current formal education programs with regard to food and nutrition knowledge and skills development as an important life skills skill. In addition, the relatively low level of FNL among high school students underscored the need for future studies focusing on FNL promotion interventions among high school students in Iran.