© Borgis - New Medicine 3/2007, s. 68-73
*Sylwia Merkiel, Wojciech Chalcarz
NUTRITION IN PRESCHOOL AGE: PART 1. IMPORTANCE, REFERENCE VALUES, METHODS OF RESEARCH AND THEIR APPLICATION. REVIEW
Food and Nutrition Department of the Eugeniusz Piasecki University School of Physical Education in Poznań
Head of the Department: Dr hab. Wojciech Chalcarz, prof. nadzw. AWF
The aim of this review was to show the importance of nutrition in preschool age, to discuss recent dietary reference values, to present currently used methods of research on dietary intake and to show their application in the assessment of nutrition in preschool children. Current studies confirm the importance of nutrition in preschool age. Special recommendations on water and dietary fibre intake for Polish children should be worked out. Researchers use various methods of research. The authors of 69 publications assessed nutrition in preschool children. Qualitative assessment was the aim of 5 published researches. Assessment of the diet through laboratory analysis was used in 6 publications. Authors of 6 articles compared the results of the chemical analysis of food rations served in preschools with theoretical estimations of the nutrient values of the same food rations. Assessment of preschool menus, reports from preschool food stocks or combination of these two sources of information were used by the authors of 5 published researches. A 24-hour dietary recall was applied in 11 publications, a food frequency questionnaire in 4 publications, a food record in 9 publications, and a weighed food record in 7 publications. The authors of 7 published researches used various combinations of different methods to assess dietary intake in preschool children. The variety of the methods applied allows various aspects of nutrition in preschool age to be shown, but also makes it impossible to compare the results.
Preschool age is a special period in human ontogenesis. Changes in body size and body proportions become slower, while all the organs and systems develop and improve their functioning, especially the digestive, respiratory and motor systems (1, 2). At the end of this period a child should achieve school-readiness, not only physical, but also mental and emotional (3, 4). One of the most important factors influencing preschool child´s development is nutrition.
The studies that have been published so far focus on selected aspects of nutrition in preschool children and there is a lack of papers summarising the results of those studies.
The aim of this review was to show the importance of nutrition in preschool age, to discuss recent dietary reference values, to present currently used methods of research on dietary intake and to show their application in the assessment of nutrition in preschool children.
THE IMPORTANCE OF NUTRITION IN PRESCHOOL AGE
Nutrition has a considerable influence on human´s health, not only in physical terms, but also mental and cognitive. Inadequate dietary intake may have a detrimental impact on a child´s health. Excess dietary intake is unfavourable, especially excess intake of energy, which results in overweight and obesity (5), as well as undernutrition, which may cause stunting and adversely affects the development of all organs and systems of the child´s body (6, 7, 8). This especially concerns the central nervous system, but also the other systems, for example the immune system, whose reaction is a decrease in immunity (7).
Nowadays, undernutrition is prevalent in preschool children who live in the poorest, developing countries and come from the lowest social classes, for instance in Ethiopia (9), India (10), Mexico (11), the Republic of Maldives (12) and South Africa (13, 14). Energy intake in those children is very low, from merely 50% of the norm (13) to only 80% of the norm (14), and is accompanied by deficiencies of many nutrients, sometimes extreme, like in preschool children from a rural community in South Africa (14), whose intake of energy from animal protein was 0%.
In highly developed countries energy undernutrition is rare and is usually the result of chronic diseases or psychosocial disorders (8). In these countries a growing problem is excess energy intake (15). However, it does not exclude the problem of nutrient deficiencies. The reason is that in highly developed countries preschool children´s diets are of low quality. Along with high energy intake they provide too few nutrients, for example, calcium and vitamin D, adequate intake of which is necessary for the proper development of the skeleton (16). Particularly adverse is deficient intake of nutrients which have a significant influence on brain development. Among these nutrients are first and foremost iron, zinc, iodine, folic acid, vitamin B12 and polyunsaturated fatty acids (17, 18, 19, 20, 21). Arija et al. (22) showed significant and positive relationships between iron intake and intelligence quotient, and between folic acid intake and intelligence quotient in six-year-old children from Spain. Eicosapentaenoic acid is of great relevance – insufficient intake may be related to attention-deficit/hyperactivity disorder (ADHD) in children, dyslexia, dyspraxia and autistic spectrum disorders (23, 24, 25, 26).
When considering the importance of nutrition during childhood, one should not forget about its influence on health later in life. The consequences of the childhood diet may be observed even in adult life (27). Qualitative and quantitative imbalance in the childhood diet predisposes to hypertension, coronary heart disease, obesity, osteoporosis and diabetes later in life (28). Preventing diet-related diseases in adulthood is delayed because raised biochemical indices of these diseases are often observed as early as in childhood and adolescence (28).
Adequate nutrition during childhood also has a psychological aspect. Dietary behaviour during childhood has an influence on attitudes toward nutrition, which is evident for the whole life (29, 30). Dietary habits formed during childhood are to a small extent apt to change later in life. Unwillingness to give up eating well-known and preferred foods is one of the most frequent obstacles in the way of a healthy diet (31). All the actions, including educational ones, aimed at promoting healthy dietary behaviour turn out to be effective only if focused on those foods which are liked and frequently consumed (31, 32).
CURRENT DIETARY REFERENCE VALUES
Dietary reference values for the Polish population were worked out by the National Food and Nutrition Institute in Warsaw. The latest were published in 1995 and include two reference values of adequate intake: safe intake and recommended intake (33). Reference values for energy and nutrient intake are not the same all over the world. For instance, in the UK there are Dietary Reference Values (DRV), which include Lower Reference Nutrient Intake (LRNI), Estimated Average Requirement (EAR), Reference Nutrients Intake (RNI) and safe intake (34, 35). In the United States and Canada Dietary Reference Intakes (DRIs) are used and they comprise: Estimated Average Requirement (EAR), Recommended Dietary Allowance (RDA), Adequate Intake (AI) and Tolerable Upper Intake Level (UL) for nutrients, and Estimated Energy Requirement (EER) for energy intake (36, 37).
It is noteworthy that Polish dietary reference values do not include water intake and include only general recommendations on dietary fibre intake with no separate advice on the intake of this nutrient for children.
Kleiner (38) claims that a child´s requirement for water is 1.5 ml per 1 kcal of energy expenditure. However, such advice is difficult to apply for an average person. Much more practical recommendations on water intake are those established for North America (39), and for Australia and New Zealand (40). According to the American advice, children aged 4 to 8 years should consume 1.7 litre of water, including water from beverages and water consumed with foods (39). Reference values for Australian and New Zealand populations (40) include total water intake of 1.6 litre for 4-8-year-old girls and boys.
Establishing reference values for dietary fibre intake in preschool children is difficult and that is why in the literature there is no unanimity on this point. Australian reference values for dietary fibre intake in 4-8-year-old children are 18 g (40). The American Health Foundation proposed that intake of this nutrient in children older than 2 years should amount to at least 5 g plus the child´s age (41, 42). The American Academy of Pediatrics suggested similar recommendation of 0.5 g per 1 kg of body weight (41). The difference is that the former recommendation, in comparison to the latter, is much more practical and easy to remember for an average person, which plays a vital role in promoting the principles of a healthy diet. The upper limit of dietary fibre intake in children should be 10 g plus the child´s age (41, 42). The recommendations on dietary fibre intake are sometimes given in relation to energy intake, that is 10 g to 12 g per 1000 kcal, and even though it was once considered excessive for preschool children (42), now it is claimed that diets with high dietary fibre content are both safe and favourable for children´s health (43). The Food and Nutrition Board of the Institute of Medicine in Washington (44) recommends 25 g of dietary fibre a day. This intake is also advised by the American Dietetic Association (45).
In Poland putting dietary recommendations for preschool children into practice is the subject of numerous publications addressed to university students, physicians and dieticians (46, 47, 48) as well as to parents and other care-takers (49, 50, 51, 52). Unfortunately, only Spock and Ponker (50) emphasised all the detailed principles of nutrition in the prevention of diet-related diseases. Polish authors falsely attach great importance to children´s intake of animal protein, butter or full-cream milk products. The issue of water intake in children was raised only by Chalcarz (53). The ultimate in false and harmful nutritional concepts are nutritional recommendations for children published in a book written especially for parents by Lansky (49).
There are very unfavourable tendencies for preschool children´s dietary intake in Polish society. Those tendencies, based on stereotypical notions, are at variance with the results of the recent studies, but are still observed in many preschools. An example is the book with preschool menus worked out by Wachnik and Weker (54) almost 20 years ago which is still in use.
Although the mortality from cardiovascular diseases in Poland is high (55), there is still a lack of nationwide actions aimed at promotion of an antiatherogenic diet. The Mediterranean, vegetarian and semi-vegetarian diets are also not popular, in spite of their well-proven positive role in the prevention of diet-related diseases.
METHODS OF RESEARCH ON NUTRITION
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