Review of the strategies employed in the school setting for the teaching of human nutrition

Este trabajo fue recibido el 26 de septiembre de 2019. Aceptado con modificaciones: 25 de noviebre de 2019. Aceptado para ser publicado: 10 de enero de 2020. ABSTRACT The main objective was to inquire about the strategies used in the school environment for the teaching of human nutrition. In addition, the existence of multidisciplinary proposals that can lead to significant learning, as well as the inclusion of the dimensions of attitude were verified. The methodological design consisted of a systematic review of studies published between 1999 and 2018, related to the theoretical reference and the type of didactic strategies that guide interventions in schoolchildren aimed at addressing the issue of human nutrition, as well as the possible difficulties that underlie them and the consequent influence on healthy lifestyles. The guidelines of EPPI-Centre were followed. In 45% of the articles reviewed an improvement was evident both in knowledge about nutrition and/or attitudes towards healthy lifestyle habits, as well as in the frequency of physical activity. Didactic proposals of diverse nature were evidenced, pointing to the protagonist role of children and adolescents and favoring their interaction through diverse strategies such as the use of ICTs (Information and Communication Technologies), games, cooperative learning and curricular integration. Nutrition education should be incorporated into school curriculum starting in early years with the active participation of teachers, family members and other community professionals. In the pedagogical and didactic approach to human nutrition, a holistic vision is necessary; this can be achieved through multidisciplinary teaching.


INTRODUCTION
In almost all countries, social and cultural factors have a major influence on what people eat, how they prepare their food, their food practices and the food they prefer 1 . While social and economic determinants play a decisive role in the quality of life and health status of communities, it is also true that access to information and knowledge can change behavior. This is why it is emphasized that guidelines, campaigns and educational practices play a fundamental role in making people aware of the best way to incorporate food into their lives and the need to be critical and objective consumers 2 .
The WHO defines health education as "the educational process aimed at equipping individuals and the community with the capacity to increase their control over the factors that influence their health" 3 . Within this perspective, there are strategies associated with the promotion of healthy nutrition habits, as a fundamental pillar that largely determines the quality of life of people in all age ranges, since the problems associated with the nutritional health of schoolchildren and the population in general each time are more frequent and diverse. The food and lifestyle behaviors of citizens are increasingly deteriorated and influenced by the pace of life and the media. The incidence of chronic diseases has been growing, so it is necessary to search for tools based on the three-dimensional concept of nutrition (biological, social and environmental aspects) to inform and provide populations with the knowledge necessary for the adoption of healthy lifestyles, an objective that will only be achieved through health education 4 . The nutritional situation is the expression not only of food balance, but also of the living conditions of the environment. While it is true that many old public health problems have been solved, it is important to note that the obesity epidemic has been increasing, especially among the most vulnerable and socioeconomically disadvantaged groups in both developed and developing countries 5 . There are different modalities of nutritional campaigns, which promote adequate nutrition for different populations (women during pregnancy, the period of lactation and the first years of life of the infant) while others focus on prevention and control strategies for the child, their families and the environment where children grow and develop. Despite these initiatives on the part of various types of entities, the coexistence of the two extremes of malnutrition (undernourishment and obesity) persist in different contexts at the global level 6 .
It is well known that a child or adolescent exposed to malnutrition conditions will be a vulnerable adult and prone to noncommunicable diseases (obesity, diabetes, osteoporosis, cancer), which is why malnutrition is considered a health priority in order to attend to the nutritional needs and good dietary habits of children and adolescents belonging to all contexts. At the global level, there is evidence of health problems among this population group, derived from the lack of nutritional education in schools, as well as from inadequate nutrition in homes 7 . It is necessary to intervene at the school level, educating teachers, students and their families in healthy eating habits 6 . Nutrition education can take many forms, however, one of the most important elements is impacting knowledge about nutrition. It is precisely at this point where it becomes relevant to explore the approach to this subject in the school context, either from the implementation of academic courses or from extra-curricular initiatives. Nutrition is a fundamental subject that is taught in the subject of science and constitutes a concept that enables the articulation of various contents (energy transfer, chemical reactions, matter and organization of living systems, that is, it integrates energy, environment and health), as well as the need to influence the healthy lifestyle habits of students, as long as it is possible to transcend theoretical notions to practical questions. In this way, it would be consistent with the premise that "the main objective of science education should be to enable all individuals to informally take part in decisions and participate in actions that affect their personal well-being and the well-being of society and its environment" 8 .
In 2002, Hoelscher et al 9 , in 14 studies published between 1994 and 2000 about nutrition interventions aimed at the adolescent population, identified that the most prominent interventions were those in which teaching strategies were based on theory, focused on individual and environmental behaviors related to food and physical activity, as well as adequate in terms of execution time. In 2016 Meiklejohn and collaborators 10 carried out a systematic review with the objective of updating the evidence on the impact of multi-strategy nutritional education interventions on the health of adolescents (ages [10][11][12][13][14][15][16][17][18] and their achievements in nutritional habits. It is important to mention that although the focus of the research included in that review was more aimed at detecting changes in the physical health of the adolescent population (mainly determined by the variation in anthropometric measures, monitoring of daily intake and frequency of physical activity), the fundamental role of nutritional education processes and strategies that result in observable and quantifiable changes is also recognized. In this regard, potentially significant interventions are those in which the following points are considered: • Adoption of measures to modify the school environment in terms of access to healthy food and compliance with school eating policies. • Requirement of an optimal and constant teacher training in current topics of nutrition. • The need to involve families and the community in training activities. • Integration of programs into existing curricula.
• The use of peer leaders and instructors. • The incorporation of student self-assessments with personalized feedback. • Use of innovative multimedia technology tools. • Promotion of a physical activity component.
The rationale for this review stems from the fact that despite multiple efforts to improve the health of children and adolescents, the problems underlying states of malnutrition persist. For this reason, the various interventions and strategies that have been implemented at schooling levels corresponding to the last cycle of primary and secondary education were tracked, as well as the perceptions of experts and training and professional teachers, in relation to the themes and methodologies that, from school nutrition education, can favor the acquisition of adequate eating habits and healthy lifestyles. The main objective was to determine what type of treatment is given to the notion of nutrition and how holistic the approach to the subject is, verifying the existence of multidisciplinary proposals that can lead to significant learning, as well as the inclusion of the dimensions of attitude as a prerequisite for the adoption of behaviors in favor of health and welfare.
The goal was to update the evidence on the preponderant strategies used in the school environment for nutritional education programs, in order to design a next step, a novel proposal that is structured from a multidisciplinary approach and that stimulates the formation of good habits in students between the ages of 11 and 13.

METHOD
The Evidence for Policy and Practice Information and Coordinating Centre (EPPI-Centre) guidelines were followed. Accordingly, systematic reviews use explicit methods to identify what can be said reliably on the basis of such studies, then synthesize research results so that they can be accessible to all those involved in the decision-making process 11 . For its elaboration, the checklist proposed by Preferred Reporting Items for Systematic and Meta-Analyses, PRISMA 12 , was used to investigate and deepen the theoretical referent and the type of didactic strategies that guide interventions in schoolchildren aimed at addressing the issue of human nutrition. Possible difficulties that underlie interventions and the consequent influence on healthy lifestyles were also evaluated.
As a starting point for the revision initiated in the last trimester of 2018, the basic search of the main collection of the Web of Science (WOS) database was used, using the following key words: "Science Education", "Nutrition" and "Food", for a total of 2,211 records. After applying the filters for "Education Educational Research", "Education Scientific disciplines", "Multidisciplinary science", "Social science interdisciplinary" and selecting only articles in English, Spanish and Portuguese, 269 records published between 1999 and 2018 were obtained. SCOPUS was then searched for the same keywords, resulting in 4,510 documents. The filter for the disciplinary field was for the categories "Social Sciences", "Arts and Humanities" and "Multidisciplinary". The total for SCOPUS was 249 articles in English, Spanish and Portuguese, published in the previously established date range. The partial total of 518 was completed with 108 Spanish records from the SCIELO database using the keywords "Nutrition" and "Education". The selection of the databases was made according to their quality, recognition among the scientific community and coverage. Using SCIELO allowed access to research developed in Latin America that had not yet appeared in WOS or SCOPUS. The title, abstract and keywords of the 626 findings were read, in order to discard those that did not fit the purpose of this review. As an initial methodology for delimiting records, seven exclusion criteria were defined and categories were formed according to the content of the documents, which are listed below: 1. Curricular proposals aimed at university students belonging to programs related to the areas of health, food science and technology. 2. Works that included interventions with patients such as: medical treatments, clinical cases, diagnoses with anthropometric measures and follow-up of daily intake. 3. Non teaching programs in educational institutions, for example: nutritional assistance or public policies directed at the student population, such as prevention campaigns, management of school restaurants, health care or physical conditioning. 4. Influence of socio-demographic factors on the population's dietary habits and nutritional status, inequities in health and/or education and food insecurity. 5. Impact of teaching strategies on topics other than nutrition (e.g. biotechnology, microbiology and genetics) and other disciplines. 6. Records that do not approach the topic of interest, since the keywords appear, but are decontextualized. 7. Systematic reviews based on other criteria.
The adoption of these criteria was based on the possibility of including research that directly pointed to the objective of the review in terms of the population group, the type of methodologies used, the pedagogical approach and its scope. After the omission of 586 records, there were 40 articles selected as potentials for the review, which were read in their entirety. As a final inclusion criterion, those studies in which the following sections were clearly and coherently detected were considered: justification, theoretical references, objectives, characterization of the sample, description of the intervention, thematic axes, research methodology and results/conclusions. The articles were classified by two independent evaluators, who periodically validated the entire process of the present review, reaching an inter-evaluation ratio of 80%. The cases that did not coincide were decided by consensus. The final sample consisted of 24 articles as shown in figure 1.
It was found that most of the studies were carried out in the United States (n= 10) 13,14,15,17,20,21,22,30,32,36 , followed by Europe (n= 6) 25,27,28,31,33,35 , South America (n= 4) 16,18,23,29 and Asia (n= 4) 19,24,26,34 . National data from the United States showed that overweight and obesity rates were higher among children from low-income families, who were more likely to have behavioral risk factors for chronic diseases 37 . Most U.S. children do not meet recommended intakes and overeat high-calorie foods, a situation that is not absent in Latin American countries and on other continents. Hence, the interest in implementing health education strategies from school age onwards is a global objective.
The methodology used corresponded to qualitative research (n= 8) 17,20,25,27,28,29,31,34 and mixed methods (n= 16) 13,14,15,18,19,21,22,23,24,26,30,32,33,35,36 , which make it possible to take advantage of the strengths of both paradigms (qualitative and quantitative) to achieve a more complete understanding of the social and educational phenomena. With regard to the characterization of the sample, the following distribution was found: students in the last years of primary education (n= 7) 13,14,15,17,18,21,35 , students of secondary education (n= 10) 16,19,20,22,23,24,29,30,33,36 , experts in health, education and related fields (n= 2) 25,34 , textbooks (n= 1) 26 and teachers in training or in practice (n= 4) 27,28,31,32 . It is important to specify that for preschool children and early education (age range not included in this review), a good number of studies have been reported, in which interaction with families is prioritized because, during early childhood, this is a key environment for children to learn and develop food preferences. As children grow and start school, teachers, peers, media and social leaders become more important 38 .
In interventions that directly addressed our population of interest, didactic proposals of a diverse nature were evidenced, pointing to the protagonist role of children and adolescents and favoring their interaction through diverse strategies such as the use of ICTs (n= 4) 19,20,34,35 , gaming (n= 3) 18,19,23 , cooperative learning (n= 2) 19,36 , curricular integration linking the topic of food with various subjects in the curriculum (n= 6) 13,14,15,17,22,29 , extracurricular programs (n= 1) 21 and optional courses (n= 1) 30 . Of these, all were carried out in the context of educational institutions, as a complement to formal planning established by grade. The sequences were applied by science or technology teachers with the support of teachers from other areas; in addition, total sequence time of between 2 days 29 and 18 weeks 30 were reported.   15 analysis of multiple courses in North quantitative data. was favored more by their knowledge regression of Carolina and Ohio. The capacity of knowledge in science of mathematics and science than by knowledge in and mathematics (independent variables) their previous notions of nutrition. nutrition, science, n= 438 students to predict knowledge in nutrition was and mathematics evaluated. Implementation of 24 lessons of fourth grade of knowledge in nutrition, science and students using the mathematics jointly. FMI curriculum.

MÉNDIZ-ROJAS
Develop an n= 1238 students of Instrumental study. The structure of the scale (attitudes ET AL, 2017 16 abbreviated version second basic cycle Application of the questionnaire in its and behaviors) responded to the of the scale of attitudes of the city of first version (attitudinal statements from need to maximize the capacity of towards healthy eating. Antofagasta (Chile). the model of attitudes, Likert type the instrument to detect possible structure). Subsequently, the measuring effects of interventions, as attitudes instrument was refined.
are more sensitive to effect than behavior.
BARTON ET AL, Report the findings n= 24 fourth and fifth Qualitative.
Although the students showed 2005 17 of a qualitative study grade students Semi-structured interviews were carried an understanding of the food carried out to find residing in New out, the central axis of which was the process between farm and market, out what children in York City. question: What happens to food this was based more on home conditions of high between the farm and the market? experiences and media information poverty think about The exploratory questions sought to than on knowledge gained at school. food and the food detect students' conceptions of system. processes related to the food system.
LIÉVANO Y Determine the n= 959 students Controlled experimental study. *An increase in knowledge was LECLERCQ, 2013 18 effectiveness of board from two public Application of a pre-and post-achieved in the children who games developed educational intervention assessment on a scale from participated in the games, as a strategy for the institutions in 0 to 100, based on a list of questions compared to those who did not; in acquisition of basic Bogotá-Colombia. related to the origin and function of food. addition, this knowledge lasted over knowledge in food The intervention phase lasted time. and nutrition, approximately two months; each week personal hygiene and one of the six games alluding to the physical activity in topic was carried out. school children.  22 that focuses on students from five quantitative data. participants' consumption of healthy providing students schools in New A 30 item instrument was designed to foods, as well as decreases in with a conceptual York City. measure the level of sedentary/physical non-recommended products. understanding of the activity and the frequency of role that biology and consumption of certain foods. the environment play The C3 curriculum ("Choice, in personal behavior Control and Change") consisted of 24 and health in order to lessons applied by science teachers over help them cope with a period of 8 weeks. Standards for the current complex biology and scientific inquiry were taken food system. into account.
FILADELFO AND Elaborate, implement Two groups of Qualitative research supported by *Most of the students improved GURIDI, 2014 23 and evaluate a students from two quantitative data. their knowledge about the nutrients didactic sequence schools, one public Application of pre-and post-test and other elements involved in the for the teaching of and one private, questionnaires, evaluation of the food and nutrition processes. food and nutrition who were in the execution of the didactic sequence: topics.
seventh year of basic Food domino education in Brazil. Trail of feeding Playful activity of reading and creation of labels with nutritional information.  Elaboration of a healthy menu.

MAHAJAN AND
Analyze whether the Tenth grade students Qualitative research supported by There was little conceptualization of CHUNAWALA, scientific information (last year of school quantitative data. the nutritional, social and genetic 1999 24 on health presented in India). Questionnaire of 32 multiple-choice aspects associated with health, in the in the biology texts is n= between 36 and questions, to investigate knowledge case of the three groups. This seems well understood by 212 depending on about different categories related to health. to be related to the way in which the students.
the stage of the these issues are addressed in research.
textbooks and during classes.

PÉREZ DE EULATE To know the ideas Creation of a The Delphi method was used to
The problems with the most valued ET AL, 2015 25 and opinions of heterogeneous panel determine the degree of consensus items were: eating disorders and professionals belonging of 21 experts among a diverse sample of sedentary life, followed by to health and educational belonging to the professionals on the competencies that malnutrition, overweight and obesity. institutions about the Human and Health students in compulsory education current problems and Sciences.
should possess, in terms of nutrition needs in the promotion and health. of healthy eating and physical activity in high school students.
RAO ET AL, 2011 26 Analyze the nutrition n= 10 textbooks Mixed approach The quantitative analysis of the and food security from grades one to The following aspects were reviewed in contents showed that fewer sections components of ten, used by CBSE each textbook: are devoted to the biological revised textbooks, (Schools affiliated to  Chapters devoted entirely to nutrition component than to the physical in terms of the Central and food security. and environmental sciences. In presentation and Commission of  Space dedicated to biology topics and addition, chapters and illustrations quality. Secondary in particular to nutrition and food issues. referring to food security are scarce. Education -India).
RIVADULLA-LÓPEZ To present the ideas n = 142 students of A qualitative study was carried out in Teachers tend to focus human ET AL, 2016 27 of the teachers in the third year of which the analysis of concept maps nutrition on the individual (their training regarding the Teaching in Primary elaborated by future teachers was decisions and repercussions on their selection of contents Education at the carried out from different perspectives: well-being), without considering on human nutrition.
University of -Concept/ purpose of nutrition sustainable development, the La Coruña.
-Systems involved in nutrition maintenance of environmental -Relationship between food and health resources and social welfare. -Relationship between food/nutrition and the environment.

RIVADULLA-LÓPEZ Know the key ideas
Teachers from 10 Qualitative study. The majority of Spanish teachers ET AL, 2017 28 that, in relation to schools in the For the analysis of the contributions of the have a medium/high level of adequacy human nutrition, teach northwest of Spain teaching staff, a dossier was elaborated in the treatment of N, while the level and evaluate (8 women and 2 men) that contemplates the four main categories of most Portuguese teachers is low. Portuguese and and 10 in the north of on human nutrition (N, concept and With respect to category A, the Spanish teachers of Portugal (9 women purpose of nutrition; S, systems that teaching staff of both groups reach 5th and 6th grade of and 1 man). intervene in nutrition; A, relationship a medium/high level in their treatment. basic education.
A total of 1332 between food and health; M, relationship For M, approximately half achieve activities and 227 between food/nutrition and environment). a high level of treatment in their evaluation issues Within each of them, subcategories were classrooms and the other half, low. were analyzed.
established, defining the corresponding units of meaning and teacher profiles.
NÚÑEZ ET AL, To design a teaching n=36 students in the Qualitative.
The analysis of the answers shows 2007 29 strategy that allows ninth grade of a Categories of analysis were defined deficiencies in aspects related to food students to identify private school in the from the productions of the students, and nutrition. The strategy favored needs and demands province of San Juan derived from the problem situations that motivation by being able to use the related to food and (Argentina  34 and interactive computer-assisted to examine the effectiveness of the students acquired basic knowledge network of linked training. system and the course. In addition, an of the digestive system from the virtual worlds that 1 human interface interview with the experts was used. course, especially from 2D and 3D can be used to designer. The name of the course was: graphics. support the health 1 specialist doctor. "Travelling with our food"; users had to Virtual reality is a viable alternative education curriculum 1 3D graphic designer. follow the path of the food as it passed as a teaching tool for those concepts (formal and informal). 1 Developer of the through the digestive tract, from the that require better visualization, as VRML application.
mouth to the anus. in the case of human body systems.
ERCAN, 2014 35 Identify changes in n= 66 fifth grade Quasi-experimental design. *The multimedia applications used academic achievement students from a A pre and post-test, a pilot test and the in the subject of healthy nutrition, and attitudes toward primary school in a final proposal were applied. As a tool for help students to become aware of the science class of province in Turkey. data collection, an evaluation o current problems that may affect fifth grade students as academic achievements was their health. a result of the use of implemented, to be answered online. multimedia materials The intervention lasted eight weeks, designed to teach for a total of 32 class hours. The user's healthy nutrition.
guide included theoretical bases on food and nutrition, consolidation activities and evaluation sections.
RANKINS ET AL, Evaluate the n = 341 students Quasi-experimental design with a mixed *The results of the students of the 2000 36 effectiveness of an belonging to the approach. four schools varied in the response innovative nutrition "Food Science and A survey with 106 multiple-choice to the application of the curriculum education curriculum, Consumer" course at questions was applied to measure the called "Live!" but in all of them, there based on the change four schools in Florida. knowledge and attitudes of the students were significant improvements in in knowledge, attitudes in relation to the objectives of the one or more of the eight categories and practices on curriculum called "Live!" This consisted on nutrition attitudes and knowledge. nutrition in students.
of five units, focused on building a knowledge base for the prevention of nutrition-related chronic diseases, as well as a component on culinary skills.
According to the synthesis of the 24 studies included in this review, it was found that five of them based their proposal on learning constructivists approaches (Vigotskian and Ausubelian principles) 13,19,23,31,34 , highlighting the role of one´s own experience and previous notions in the process of knowledge elaboration. The importance of significant learning was made explicit in five of the studies 23,27,29,33,35 ; three took into account the approaches of Vygotsky 19,20,36 , who considerd educational processes as a product of social interaction. Five of the interventions were based on the inquiry teaching methodology which helps children ask questions and develop a better understanding of topics of interest.
It is worth mentioning that 33% of papers 16,19,22,25,30,32,35,36 . were interested not only in imparting knowledge about nutrition, but also in prioritizing the change in attitudes and behaviors as a measure of the real impact of the intervention. The design and evaluation of these proposals were based on the cognitive component of attitude, considered as a psychological tendency expressed through the favorable or unfavorable evaluation made on something 16 . The theory of planned behavior was also taken as a basis, which states that the most immediate mediator of change in behavior is intention; which in turn is influenced by attitudes toward it 22 . It was possible to integrate the cognitive aspect, the metacognitive and the socio-affective factors, in the construction of a proposal oriented to the motivation for regulation in one's own habits, reflected in attitude changes 19 .
For this reason, in addition to the main and common thematic axes such as: food groups; food security; food hygiene and handling; types of nutrients; nutritional pyramid; food labelling; nutrient deficiency and diseases; relationship between diet/nutrition and the environment; and systems involved in nutrition, emphasis was placed on healthy eating habits and the relationship between well-being and food practices, such as adequate consumption of: fats and oils, vegetables, dairy products, fruits, meat and protein, grains, micro and macro nutrients 19 .
In relation to the results obtained, the comparison of the pre-and post-test scores showed statistically significant differences for the intervened groups in 11 of the studies 13,14,15,18,19,21,23,30,33,34,36 , reporting an improvement both in knowledge about nutrition 13,21,23,33 and/or in attitudes towards healthy lifestyle habits 19,30,35,36 and in the frequency of physical activity 14,15,18 . An important finding was the absence of longitudinal studies confirming the permanence of these changes over time. Long-term assessments are required to determine whether this knowledge is reflected in changes in attitudes and improved health conditions 18 .
Some of the components of interventions assessed as effective were: experimental practices 13 , learning by scientific inquiry 14 , implementation of science and mathematics lessons in an articulated way 15 , use of play 18,19,23 , activities mediated by technological resources 19,35 , routines of physical activity 21 , elective courses (optional subjects chosen according to the student's preferences) for curriculum immersed in nutritional education 30 , tasks of classification and categorization of food groups 33 , culinary skills workshops and academic debates 36 . An improvement was evidenced in the cognitive aspect related to knowledge about nutrition, mainly in those proposals based on curricular integration, the use of ICT and teaching through gaming. The strategies that took into account reflection and self-monitoring, as well as the development of critical thinking skills, also showed favorable results in terms of attitudes towards healthy eating and the modification of some habits and routines.
In these studies, the proposed methodology was assessed as pertinent and favorable, the formulated objectives were met, and improvements were detected in at least one of the cognitive or behavioral components evaluated. According to the reported data, there was a moderate increase in the consumption of healthy foods and in the frequency of physical activity 21 .
Students also showed some changes towards the belief in the advantages changes represent for health, making good decisions regarding food choices 22 , recognizing that nutrient and calorie excess is detrimental to health. In addition, there was an adequate internalization of knowledge with respect to the reading and interpretation of nutritional labels 23 .
The students' conceptions and difficulties with regard to food properties and healthy lifestyles were investigated in this revision 17,24,29 . The lack of recognition of scientific principles underlying the biological dimension of health 24 was highlighted, with micronutrients being the topic that represented the greatest complexity 13 . The topic of active compounds in food aroused the interest of both teachers and students, who consider it important to relate the presence of certain chemical constituents (vitamins, dietary fiber, iron, antioxidants) with their impact on human health 31 . A conceptual obstacle was detected for students who are not aware of their energy demand or how to meet it 29 . Furthermore, they have the notion of a food as a product processed in a factory and offered in a market, not as a derivative of nature whose function is to satisfy a person´s nutritional needs 17 . The lack of conceptualization of nutritional aspects associated with health seems to be related to the way in which these issues are addressed in textbooks and during classes 24 . Coupled with the above, the time invested in nutrition education in the classroom is insufficient to result in stable changes in the knowledge, attitudes and habits associated with food 25 .

Discussion and implications
In all articles reviewed there was a clear and solid justification regarding the pertinence of implementing nutritional education strategies from school, based on the need to educate children and young people on healthy eating, in line with the WHO initiative, which seeks to promote nutritional programs in schools 35 . One of the most important elements is to impact knowledge about nutrition 13 through the joint work of health professionals and school principals with teachers, in accordance with the respective standards 15 . Although there are education programs in sciences oriented to nutritional well-being, it is rare that teaching is linked to a multidisciplinary approach 14 .
Macias and collaborators 4 start from the problem of considering nutrition as a purely biological aspect, which limits actions aimed at improving the nutritional situation of the current population. In the proposals of the studies included in the present revision, it was evident that the integration among different subjects and school projects, allows for significant learning, as well as the application of the knowledge in everyday life situations 13,14,15,22,29 . Human nutrition could be associated with the transfer of energy, chemical reactions, matter, and the organization of living systems, that is, the integration of energy, environment, and health 15 . It was also proposed that teaching of biology (as well as other disciplines), needs to be articulated with health topics in a meaningful way for students 24 , and that the combination of instructional activities and living-practices can promote significant improvements in dietary habits 19 .
Intervention in schools on the subject of nutrition is complex, since it does not form part of the curriculum and may represent an extra burden for educational institutions, which tend to be more concerned about the performance of students on standardized tests 7 . That is why their approach in the school setting is still very poor despite the different measures and policies that have emerged in this regard 26 .
When comparing the theoretical and methodological bases of nutrition education programs for healthy eating aimed at the school community, the analyzed studies start from the premise that traditional methodologies do not tend to be very effective when it comes to influencing changes in habits associated with quality of life and food. Thus, problems persist and are related to low academic performance, poor school coexistence and lack of selfesteem among the student population. Innovative models of food and nutrition education should be developed that consider existing knowledge and consumption habits of students, parents and teachers 7 .
Teacher training should have a greater impact on the analysis of the importance of human nutrition on the environment and on the very concept of nutrition 27 . Access to current training resources is required to facilitate didactic planning and improve learners' interest in developing healthy living skills through a balanced diet 31 . For this reason, emphasis is placed on the need for students to understand this vital function from a multidisciplinary perspective, in which the set of theoretical knowledge is articulated with significant and motivating work experiences, in order to have a favorable impact on the daily practices and lifestyles of the student population. Although there are several studies in the literature that report variations in diet quality in terms of daily intake and improvements in physical conditions based on anthropometric measures, these proposals are not necessarily immersed in the school curriculum and may present disadvantages such as the fact that sessions become very long after students have spent most of the day in school 37 .
Learning science implies being able to use scientific knowledge (of and about science) in everyday life situations -also called contexts-to make responsible decisions 39 . In spite of the arguments in favor of nutritional education programs with a view towards integration and interdisciplinarity, in this review we found that only 17% of the studies implemented a methodology consistent with this perspective, considering nutrition from its personal and social dimension 13 . Thus, nutrition was articulated within the subjects of biology, microbiology, chemistry and mathematics 14,15 . In the treatment of this concept, natural sciences, social sciences, technology, mathematics and language were also addressed together 29 .
Previous reviews have investigated the basic aspects that contribute to the effectiveness of nutritional care programs in schoolchildren 9,10 , among which the following stand out: convenient time and intensity, family participation, multi-component strategies, appropriate teaching methods, modification of the school environment (access to healthy food, school feeding policies, school meals), teacher training opportunities, capacity to strengthen skills and influence attitudes. Bearing in mind that one of the key factors is teaching strategies based on the acquisition of knowledge about nutrition and its impact on healthy lifestyles, it is essential to investigate what types of methodologies have been taught in recent years in order to determine how relevant and motivating they are for the student population.
Returning to the aspects synthesized by Meiklejohn et al 10 we found coherence between these and the studies of the present review, in terms of: the need for teacher training 27,28,31,32 , the participation of the family environment 21,36 , the immersion of programs in existing curricula 13,14,15,17,22,29 , the advice of leaders and specialists 25,34 , the use of feedback strategies 19,30 , the use of ICTs 19,20,34,35 and the incorporation of physical activity practice 14,15,18,21 .
As a product of this systematic review, the relevance of including as a key point (in addition to curricular integration and multicomponent strategies), the holistic treatment of human nutrition from a multidisciplinary approach among the different areas of knowledge is validated. It also clarifies the need to introduce strategies and indicators that reflect attitudes towards healthy eating and the modification of habits in the medium and long term.
Nutrition education programs that articulate the multicomponent trend of extra-curricular campaigns with appropriate teaching strategies for schools can favor significant learning. This will contribute to promoting changes in attitudes towards healthy eating among children and adolescents, since, despite the initiatives and insistence of government policies, the percentages of malnutrition conditions and their respective consequences continue to show alarming figures in different contexts. It has been postulated that the more integral and sustained the educational interventions to promote patterns of self-care and healthy lifestyles from childhood are, the more positive and lasting the effects (WHO, 2004).
This perspective validates the appropriateness of using active learning methodologies that include several strategies such as those referenced in the studies included in this review that aim both at conceptual appropriation of nutrition topics and at determining whether this knowledge is reflected in changes in attitude and better health conditions in the intervened population. It is necessary to investigate the permanence of these habits in the medium and long term, in order to fulfill the fundamental role of the educational system in the scientific understanding of the different aspects of health on the part of students and in the promotion of healthy life practices in them 24 .

CONCLUSIONS
The study of human nutrition has high educational value, focusing not only on the scientific aspect of anatomy and physiology, but also on the relationship with the environment and health 27 . In addition, some positive changes in students' attitudes towards food consumption habits can be detected, bearing in mind that food is an excellent teaching tool because people have previous knowledge based on their own context 14 . This, in turn, can be reflected in the good health of young people and in the reduction of the problems associated with overweight and obesity 30 . It is important to emphasize that to be successful, nutritional education must be incorporated into the school curriculum with the active participation of teachers, family members and other community professionals.
In the pedagogical and didactic approach to human nutrition, a holistic vision seems to be necessary. This can be achieved through a multidisciplinary teaching proposal that provides nutritional education from various dimensions of knowledge and allows students to be consistent in applying information acquired to their daily lives. Since little research was found in this area for our age range, future research is needed to explore the impact of an integrated approach to nutrition education at different levels of schooling 13 .