Keywords

1 Introduction

Food choices affect the health of every human being and if not balanced, could lead to various diseases or malfunctions of the organism (Botero & Wolfsdorf, 2005). Nowadays, we are able to access a variety of information about healthy eating in every stage of life. Regarding childhood, it is argued that a healthy diet during these years will contribute to good health and physiological development, thereby leading to better school performance (Worobey & Worobey, 1999). According to Neufeld et al. (2023, 21) “a healthy diet is health-promoting and disease-preventing. It provides adequacy, without excess, of nutrients and health-promoting substances from nutritious foods and avoids the consumption of health-harming substances.” Moreover, according to Pérez-Rodrigo and Aranceta (2001), the adoption of healthy eating habits by adolescents is accompanied by healthy life practices, including physical activity, avoidance of smoking, and stress management, which could reduce the effects of chronic diseases later in adulthood. However, a variety of factors, including cultural and economic ones, play a role in the composition of a healthy diet because the respective combination of foods that make up the diet is context-specific (Neufeld et al., 2023).

However, do adolescents consume healthy food? When talking about adolescents’ nutrition, it is important to distinguish between what they should eat and what they generally prefer to eat. Obviously, the latter arises from both personal preferences and the strong social norms that are created by peers, which are often adopted both voluntarily and involuntarily due to the vulnerability of adolescents (Pirouznia, 2001). For example, very often adolescents’ outings include junk food (i.e. fast food) and snacks that are particularly high in calorific value, but low in nutritional value (e.g., chips, soft drinks, doughnuts, ice cream, pizzas, and others) (Word Health Organization, 2018). It is evident that such a diet contributes to obesity, and may cumulatively cause other types of diseases. On the other hand, there are other adolescents who also acquire health-damaging eating habits: Very strict diets are generally popular among the ranks of adolescents since it is believed that diets can ensure a very lean and, by social standards, beautiful body. Therefore, they are eager to reduce their daily food intake, sometimes resulting in cases of malnutrition which can lead to very serious conditions (e.g., anorexia nervosa) (WHO, 2018).

These practices lead adolescents far away from following a balanced diet that contributes to good health and the proper functioning of the body. In fact, they have an increased need for minerals such as calcium and iron during this stage of life due to the development of the musculoskeletal system and the onset of menstruation in girls. Vitamin intake should also be at high levels (e.g., vitamins D and K). Regarding energy requirements, it is not possible to generalize because there are significant variations from person to person, depending on their particular characteristics and choices (i.e., growth rate, physical activity, and other factors). (Brown, 2016).

1.1 International Research of Adolescents’ Nutrition Knowledge

Several studies (Barzegari et al., 2011) have shown that, nutrition knowledge and attitudes towards nutrition are rarely not directly related and, more specifically, there is generally a positive correlation between nutrition knowledge and adolescents’ eating habits. In other words, if adolescents had adequate knowledge about nutrition, they could probably make better choices about the foods they consume. This lack of basic knowledge about nutrition leads to many misconceptions, which are not limited to issues relating to food composition, but also extend to eating habits (e.g., recommended portions from each food group) (Sakamaki et al., 2005). In a recent survey of adolescents in Turkey, Saribay and Kirbas (2019) found that more than 65% of the participants had a very low level of knowledge about nutrition concepts. Similar results were reported in Pirouznia’s (2001) research conducted in the US: Once again, it was shown that adolescents’ nutrition knowledge was poor. Finally, Kostanjevec et al. (2012) identified that Slovenian adolescent students also had limited knowledge of nutrition concepts. These results were in accordance with those of Barzegari et al. (2011) in Iran, and the recent findings of Mizia et al. (2021) in Poland.

Moreover, nutrition knowledge has been found to vary according to the field of study chosen by secondary school students: In countries where nutrition and physiology programs are implemented, mainly through the subject of physical education, students participating in those programs had an improved perspective of nutrition. Nevertheless, even their performance level is not satisfactory, since similar performance is recorded for students with different educational orientations (Barzegari et al., 2011).

1.2 Nutrition Knowledge of Greek Adolescents

In Greece, research on adolescent nutrition (Varelas, 2006; Tsamita et al., 2007) focuses mainly on habits rather than nutrition knowledge, and even that is quite limited. Hassapidou and Bairaktari (2001) found that Greek adolescents do not choose a well-balanced Mediterranean diet, resulting in a reduced intake of essential nutrients from the foods they prefer to eat, thus preventing proper physiological development. At the same time, there is an increase in the consumption of unhealthy foods which are rich in fat and sodium (Hassapidou & Bairaktari, 2001) in their daily lives, and a reduction of the consumption of fruits and vegetables (Bebetsos et al., 2015). It is no coincidence that Greece ranks first in Europe in childhood (7–9 years old) obesity and third in adolescent (15 years old) obesity (WHO, 2018). Finally, the curriculum dealing with the concepts of nutrition involves only four teaching hours in K7, and those occur in the home economics class, rather than in the science class. Ιf we combine all of the above, it becomes clear why teaching students about food and dietary choices beginning in the early school years is really important: This kind of knowledge could contribute to healthier habits during and after adolescence.

In order to enhance Greek adolescent students’ knowledge about nutrition, we decided to create educational opportunities outside of and/or complementary to the formal education framework: We planned to introduce educational games, treasure hunts, and other activities as a means of evaluating students’ nutrition knowledge after these tools had been implemented in the classroom. However, in order for the tools to effectively achieve our goal, it was first necessary to identify students’ existing knowledge, especially since this had not been systematically assessed in Greece. Thus, the purpose of this study was to capture a first picture of Greek adolescent students’ knowledge about nutrition in order to better guide our next step, i.e., the creation of appropriate educational tools. Details of this first phase are presented below.

2 Research Design and Method

2.1 Participants

In this study, 269 students aged 15–16 (50.9% girls, 49.1% boys) from different public schools across Athens participated. Schools were randomly selected, and the students were all of middle socioeconomic status; according to their teachers, they were average achievers. We decided to work with students of this age since it marks the end of compulsory education in Greece. Moreover, we restricted the sample size because our research is not a pure statistical study, but rather an initial collection of trends in order to accumulate some useful information on where to focus the educational tools we plan to create in the next phase.

2.2 Research Tool

To conduct our survey, we used the General and Sport Nutrition Knowledge questionnaire (GeSNK) (Calella et al., 2017), a questionnaire of 29 close-ended questions created for secondary students. The questionnaire is divided into two parts: The first refers to general knowledge about nutrition, and the second explores attitudes of students involved in different sports. For the purpose of our study, we used only the first part of this questionnaire as the two parts are separate and, more importantly, our intention was not to evaluate the differences in nutrition knowledge between students who are athletes and those who are not. It should be noted that while the first part of the questionnaire had 29 major questions, some of them contained sub-questions, which resulted in a total of 63 questions. For each question, the participants could choose the answer they considered correct from the given options. Τwo additional questions were also included in the research tool: the gender of the participants, and their source of information on nutrition issues (indicated by choosing from among different options, and/or by adding a source of their own). The questionnaire was translated into Greek by one researcher, and then translated back into English by the second researcher to ensure the correctness of the translation; it was then converted into electronic form to ensure the anonymity of the students, and for easier and safer distribution in compliance with COVID-19 health measures then in effect.

2.3 Data Collection and Analysis

The research was conducted in January 2022. The questionnaires were completed by the students within 45 min in each school’s computer room in the presence of a teacher, who did not participate in the process except to supervise its smooth execution. The students’ answers were automatically saved and uploaded after students’ submissions, and the data were retrieved and analyzed by the researchers. More specifically, the analysis was initially done for all the students as a group, and then each student’s responses were analyzed individually. Each correct answer was awarded one point. Therefore, as explained above, the maximum possible score for each student was 63 points, and for the total number of students it was 16,947 points (269 (×) 63). Answers were also analyzed on a question-by-question basis to show the possible lack or sufficiency of the students’ knowledge regarding the various issues included in the questionnaire. Finally, we examined whether there were differences in participants’ scores based on gender. This type of analysis aims to provide a more complete picture of Greek adolescent students’ general nutrition knowledge, which, as has been discussed above, is something that does not exist at present. The results will point to areas where more weight should be given when designing similar teaching interventions, educational programs, and teaching and learning materials.

3 Results

The results of the aggregate scores of the participating student population for all questions are presented first, along with the percentages of students who scored correct answers, followed by the students’ results on some of the individual questions, i.e., mainly those questions that showed maximum or minimum score values, or those that had a broader categorization. Cronbach’s alpha coefficient for the GeSNK General Nutrition section, which we used in the present study, was 0.857.

3.1 Findings for the Aggregate of the Participants

Students correctly answered slightly more than half of the questions. The overall percentage of correct answers for the aggregate of the participants was found to be 57.3%, i.e., the total score of all the students combined was found to be 9704 points out of a maximum possible score of 16,947.

Table 14.1 presents the aggregate results in percentages of correct answers in the total population of participants, as well as the distribution of scores between genders. It is important to mention that the maximum score was 85.7% and was achieved only once, while the second maximum score of 84.1% was achieved three times. The minimum score of 0% was achieved once as well, with the second minimum score of 6.3% achieved four times.

Table 14.1 Αggregate results of correct answers to the GeSNK questionnaire
Full size table

3.2 Analysis of Answers to Individual Questions

In the first eight questions (including the sub-questions), students were asked about the nutrient contents of different foods. The answers to each question were analyzed individually, and the results are shown in Table 14.2.

Table 14.2 Percentage of correct answers per nutritional component of different foods
Full size table

Regarding the carbohydrate content of six different foods, a total of 65.3% correct answers were found, although 197 students considered tomatoes to be rich in carbohydrates, while 198 gave the same answer for cereals; the majority (205 students) correctly identified bread as a high carbohydrate food. In the protein category, 64% of the answers were correct, but only 128 students correctly identified beans, while cod was considered by 93 students as containing low/no protein. Low scores were observed for fiber, i.e., only 30.5% of the answers were correct, and for calcium and potassium content (47.21% and 45.91% correct answers, respectively).

On the other hand, the finding of 63.8% correct answers about iron was encouraging. However, a deeper look showed that many students considered apples (67 students) and honey (72 students) to be sources of iron. It was also encouraging that 61.86% identified foods containing high amounts of salt (i.e., canned foods such as peas, tuna, and others), although 166 participants did not consider bread to contain added salt. Finally, the category of fats had the highest percentage of correct answers: 76.27%. Surprisingly, some 37 students did not consider salami as a fatty food; 32 students did not recognize butter as being fatty; while the same was true of 59 students’ idea about mayonnaise. However, according to 102 students, jam was noted as a food rich in fat.

Questions 9–23 were true-false questions without a specific categorization, which resulted in both encouraging and disappointing findings, e.g.: 53.53% answered that “egg white has a high cholesterol content,” and 68.4% thought that “a high energy food is necessarily a fatty food.” Furthermore, 46.5% noted that “dairy products are a good source of iron,” while only 44.2% believed that “a variety of foods did not contain added salt.” Furthermore, about half (47.3%) did not know that “omega-3 and omega-6 are fatty acids,” and more than one-third (33.5%) did not know that “dried fruit is a good source of essential fatty acids.” However, a large percentage (72.9%) responded that “carrots are a good source of vitamin A,” that “our bodies produce vitamin D through our skin directly from sunlight while we are outdoors” (72.1%), and that “canned products contain more salt than dried products” (71%).

The last six questions (24–29) dealt with nutrition and health issues. For the question as to whether “in obesity, diet plays an important role, while physical exercise does not,” 77.7% answered correctly, while for the question as to whether an “unbalanced diet is the only risk factor for the development of cardiovascular diseases,” the correct answers were found to be lower (59.48%). Finally, 58% noted that “in order to achieve a healthy weight loss, carbohydrates should not be removed from the diet.”

Regarding their sources of nutrition information, the Internet ranks first (62.1%), followed by parents (61.3%), by coaches (39.1%), and then by teachers and school nutrition programs, both with exactly the same percentage (33.5%). Friends, television and extracurricular nutrition programs complete the main sources of information, while many people noted that they have no knowledge of healthy eating. Also, several students noted other sources, such as a nutritionist, a pediatrician, and other specialists.

4 Discussion

Through this research involving 269 Greek adolescent students, we found that their level of nutrition knowledge is only moderate. In fact, the aggregate number of correct answers to our research tool was only 57.3%, indicating that the number of students lacking nutrition knowledge is significant. Our findings are in line with those of other international studies, which also identify deficits in adolescent students’ knowledge of nutrition issues. As mentioned above, studies in European countries, as well as in Asian and American countries (Barzegari et al., 2011; Mizia et al., 2021; Pirouznia, 2001; Sakamaki et al., 2005; Vaitkeviciute et al., 2015), have found that adolescent students are unaware of basic nutrition concepts.

In the present research, this is reflected through a limited number of correct answers on our research tool, leading us to identify what the distribution of the students’ levels of successful (correct) answers was (Table 14.1). The analysis shows that 52.8% of the students managed to correctly answer up to 38 questions out of the 63 in the questionnaire (i.e., 60% of possible correct answers). This means that a large number of the students have a very basic knowledge of nutrition issues. However, if we look at the percentage of students who achieved higher scores (i.e., >70%), then the percentage of students with a very basic knowledge of nutrition issues drops to 18.2%. In other words, only 49 out of the 269 students managed to correctly answer more than 45 of the 63 questions, while only 11 managed to correctly answer more than 50 questions. While we did not expect students to achieve a score of 100%, certainly a performance close to 50% by almost half of the participants cannot be considered satisfactory, as it indicates that there is a significant lack of nutrition knowledge.

In addition to getting a first overview of the level of the students’ nutrition knowledge, it was important for our purposes to identify the aggregate success rate of the participating students. As can be seen in Table 14.1, the majority of students (i.e., 27.1 + 23.8 = 50.9%) are ranked in the 60–70% and 50–60% success ranges. This could be considered a positive sign in the sense that the majority of the students’ scores are not concentrated in lower ranges. However, if we observe the rates above 70% and below 50%, we find that for <50% we have a population of 29%, while for >70% we have 18.2%, i.e., students who have insufficient nutrition knowledge outnumber those who have a higher level of knowledge. It is therefore clear that within the participating student population there are several students of different knowledge levels. This certainly needs to be taken into account when designing an educational proposal on nutrition.

In order to further identify weaknesses and/or strengths in the students’ nutrition knowledge, an analysis of each question individually followed. Again, the results varied considerably, but it now became more apparent what the students know as absolutely basic knowledge, what possibly constitutes for them more specialized information about something they already know, or even what information they have previously not come into contact with. For example, the general and widely known categories of nutritional content were found to be more familiar to the students, and therefore we observed relatively satisfactory rates of successful responses. In particular, carbohydrates, proteins, and fats were obviously within the students’ range of knowledge, so success rates relating to questions about these elements were roughly in the range of 64–76%. However, there were striking qualitative deviations from the correct answers, as has been discussed in detail in Sect. 14.3.2 above. Therefore, if we look at the general picture of what the students know about nutrition, we may be partially satisfied, but an in-depth look reveals the misconceptions (or perhaps the ignorance) that exist among the students.

Furthermore, the variety of answers to the true-false questions ultimately shows once again that the adolescent students have fragmented knowledge about nutrition: They do know some things about vitamins (e.g., where we get vitamin A from, or how vitamin D is produced), but they assume that any food with a high calorific value is necessarily high in fat. Specifically, a number of the students (>2/3 of the participants) consider that “dried fruit is a good source of essential fatty acids”. If we combine this answer with the one about jam previously discussed, we would say it is likely that the students think that any food with a high calorific value includes fat. It is therefore possible that sugar and fat are not sufficiently distinguished by many of the students, who associate them with their high calorific yield and not with their other, substantive characteristics. If this is indeed the case, it could have dangerous implications for their health.

Regarding the students’ answers in relation to nutrition-health issues, as represented by the last six questions of the research tool, we found that while many (77%) acknowledge that both poor nutrition and lack of exercise are responsible for obesity, fewer (59.5%) believe that the same is true for cardiovascular diseases. Therefore, according to the beliefs of the students, exercise is a habit to avoid obesity rather than a habit that promotes health. Let us not forget, as previously mentioned, it has already been found (WHO, 2018) that adolescent students (especially girls) resort to extreme diets, investing heavily in their physical appearance, which requires a slim body according to social norms; in addition to diet, exercise is considered as a way to achieve this. Cardiovascular diseases and their prevention are not among the students’ interests, so that their knowledge about these issues is more limited. Finally, it is worrying that 42% of the students believe that carbohydrates should be eliminated from their diet in order to lose weight. Obviously, this skewed view not only indicates a lack of knowledge, but also raises the alarm about possible health disorders that may arise in adolescents if they follow such practices.

It is also worth commenting on the fact that no particular gender differences were observed between the number of students who performed similarly, with the exception of the high percentages achieved by more girls than boys (in the sense of absolute numbers rather than strict statistical tests, which are beyond the scope of this research). This slight predominance of girls is also confirmed in Pirouznia’s (2001) survey. However, what is noteworthy is the sources of nutrition information reported by the students: While parents come second after the Internet as a source of information for the students, school and teachers come quite a bit later, although they should be a primary source. The students’ thirst for learning about nutrition is reflected by the Internet being first in the list of information providers. The gap that exists between the students’ level of nutrition knowledge and the school programs focusing on this is, therefore, evident. However, there are also several individual responses: “I looked it up myself,” “from my pediatrician,” “from a nutritionist,” “I looked it up while in quarantine,” and others.

All this suggests that while the students obviously would like and need to have more knowledge about nutrition, their sources of information can be fortuitous and possibly not always reliable. For example, although one would expect that the vast majority of the students would know that omega-3 and omega-6 are fatty acids, mainly because there is a daily bombardment of television advertisements featuring products enriched with these ingredients, in the end only about half (47.2%) were aware of this, even though television is among their sources of information.

It is noteworthy that even students who achieved high scores for their responses to the research tool noted, in addition to indicating their nutrition information sources, that “I have no knowledge of healthy eating.” This shows a lack of confidence about what they know, and could even harbor a warning that they might have chosen answers randomly, which may need further investigation. The need not just for knowledge acquisition, but also for socio-scientific reasoning skills to be cultivated around similar issues is also reflected (Georgiou et al., 2020a, b; Maniatakou et al., 2020). At the same time, we must also consider the limited number of participants in the study, the results of which may indicate some trends in the Greek adolescent students’ nutrition knowledge, but is not generalizable to the total population of Greek adolescent students.

As has already been mentioned, the present research is a first step in the subsequent construction of appropriate teaching tools in order for students to come into contact through education with concepts relating to nutrition more effectively. However, we believe that our findings are not limited to Greece: The lack of knowledge about nutrition is an issue that reflects not only on the cognitive level of students, but also on health issues they may face as human beings due to eating habits. It is, therefore, important to conduct similar surveys and compare the results to identify possible patterns in the deficiencies that students may have. In this way, educational tools that transcend the borders of a single country and that can be shared and implemented in larger populations could be built/designed, with the first aim of improving personal nutrition knowledge, and the ultimate goal being the permanent adoption of desirable attitudes and habits.

In our study of Greek students, only one part of the questionnaire (i.e., general nutrition) was tested, and an in-depth analysis of the data was carried out, constituting the Greek context of students’ nutrition knowledge. It should be noted that the GeSNK questionnaire has already been tested for its validity and reliability by researchers in Spain (Manzano-Felipe et al., 2022), Turkey (Gokensel Okta & Yildiz, 2021) and Romania (Putnoky et al., 2020), who created the Spanish, Turkish and Romanian versions of the GeSNK, respectively. In Spain it was found that 59.1% of the respondents have a low level of knowledge, while similar findings were found in Turkey and Romania. In line with previous surveys (with other tools) described in Sect. 14.1.1 of this chapter, a lack of knowledge in this area has been confirmed. Additionally, the need to create appropriate educational tools is further intensified and their effectiveness can be tested even through comparative studies and collaboration of the research community.

5 Conclusion

The present research was conducted to obtain a first picture of the level of nutrition knowledge of Greek adolescent students in order to prepare appropriate learning tools for nutrition concepts (e.g., educational games, treasure hunts, and other activities). The students’ responses to nutrition-related questions on the GeSNK research tool allowed us to identify areas in which the students had a lack of nutrition knowledge, leading them to have misconceptions about food values and healthy eating habits. In fact, we found that it should not be assumed that any basic nutrition knowledge can be excluded on the grounds that it is already known to students, since our analysis identified students of different knowledge levels. The study also revealed that the students do not receive adequate nutrition information from their school program, but turn to other sources for information, some of which may not be valid or reliable. These findings will guide us in planning and implementing appropriate learning and teaching tools which will meet students’ needs.