NUTRITION OF PRIMARY SCHOOL CHILDREN

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NUTRITION OF PRIMARY SCHOOL CHILDREN

There is general consensus that appropriate eating habits of children are important for optimal physical and cognitive development, the attainment of healthy weight and the reduction of the risk of CNCD.¹⁶ In order to achieve nutritional health many organisations and countries have set up dietary guidelines, including South Africa, where country-specific, evidence-based food-based guidelines for people seven years and older were officially approved and adopted by government in 2003.
Knowledge of current eating habits of children relative to these dietary guidelines and reference intakes is an important starting point for appropriate intervention for maintenance or improvement of the nutritional status of children. In the following section some major findings of relevance to the current research context are presented, first from the international literature and then from South Africa.

Eating habits of children

Dietary intake data of children on the international arena suggests the following:
Amongst eleven to 18-year-old United States (US) adolescents from 1965 to 1996 total energy intakes decreased, as did the proportion of energy from fat (from 39% to 32%) and saturated fat (15% to 12%). There were concurrent increases in consumption of higher fat potato and mixed dishes (pizza and macaroni cheese), lower fat milk replaced higher fat milks, but total milk consumption decreased by 36%.⁵¹ Ten-year results of the NHLBI Growth and Health Study showed that for girls total and saturated fat and cholesterol intakes had decreased with age. In all cases the decrease was more in white girls than in black girls. A substantial percentage of both ethnic groups had not yet reached NCEP goals in terms of PFE, PSFE and cholesterol.⁵² Even children known to be at high risk for cardiovascular disease (based on the NCEP criteria) were no more likely to meet guidelines for heart-healthy diets than were children at low risk.⁵³
Dwyer et al ⁵⁴ investigated the eating patterns of US adolescents and found that an increase in eating occasions was common. It was associated with increased energy intake but a reduced relative amount of total and saturated fat consumed. ‘Grazing’ may be the modal behaviour of children who also increasingly make their own food decisions.⁵⁵ A high percentage of daily food intakes of children occurs at schools. In the US, school stores were found to sell primarily snacks with high fat and sugar content.⁵⁶ Amongst participants in the Bogalusa Heart Study, Nicklas et al ⁵⁷ reported a striking change in meal patterns over a 21-year period: They observed increases in the number of meals eaten away from home and at restaurants, decreases in home dinners, snacking and total eating episodes.
A recent review of current dietary trends and quality, including evidence of tracking of nutrient intake in children, as well as meal patterns, frequency and portion size information in US children aged two to eleven years has been compiled by the Ameican Dietetic Association (ADA) ¹⁶ and may also be relevant for older children and adolescents.
Hackett et al ⁵⁸ studied eating habits of eleven and twelve-year-old children before and after the start of a healthy eating campaign in the United Kingdom (UK). They found favourable changes, but also that the “case for encouraging changes in the eating habits of children is compelling”. This was confirmed by national and regional surveys of 11 to 14-year old UK children where the most popular items emerged were the least desirable foods: Confectionary (crisps, chocolates, sweets), biscuits and cakes, chips and sugar-flavoured fizzy drinks.⁵⁹ The dietary trends amongst Scottish school children in the 1990s suggest increased intakes of fruits and vegetables (but still below recommendations) and concomitant increases in high-fat and high-sugar foods, the latter particularly amongst boys and children from lower socio-economic groups.¹³ A study of 158 German primary school children showed that they consumed 42% of energy from fat with about 50% as saturated fat.⁶⁰
For South Africa national data for children are limited to the age group one to nine years.⁶¹ Very few studies addressing children are included in a report on South African food consumption studies undertaken amongst different population groups between 1983 and 2000.⁶² The THUSA Bana study focused on people in transition in the North West Province and included 1257 children, of which 868 in the age group ten to 13. Maize porridge, white sugar, brown bread, full cream milk and white bread were the most commonly consumed foods.⁶² Over 40 years ago (1962) the nutritional status of six to eleven year-old white primary school children in Pretoria was surveyed in depth. At that stage percentage energy as fat, protein and carbohydrate were reported to be 35%, 12% and 53% respectively. It was concluded that the nutritional status was equivalent to that of an “affluent population group.” ⁶³

Dietary fats in childhood nutrition

One of the US Dietary Guidelines 2000 for the general population states: “Choose a diet that is low in saturated fat and cholesterol and moderate in total fat.” ¹² The equivalent in the food-based dietary guidelines for South Africa is: “Eat fats sparingly.” ¹³ The NCEP report of the Expert Panel on Blood Cholesterol Levels in Children and Adolescents ¹⁷ recommends the following intakes in the Step 1 diet:

The American Heart Association Guidelines ¹⁵ reiterated the above as being population guidelines, which should also apply to children and adolescents.
Butte ⁶⁴ reviewed the optimal fat intake for children against the background of their energy requirements. They state that the current recommendations of 30% of energy from dietary fat for children older than two years are sufficient for adequate growth. Lower intakes may be associated with micronutrient inadequacies. Higher intakes may lead to increased energy intakes and increases in body fat, but conflicting data are available.
In industrialised countries the conclusion thus seems to be that the primary prevention of CNCD should begin in childhood  but there is no agreement on the most appropriate application, for example the US versus Canada regarding the best age from which to recommend these intakes.⁶⁶ In many developing countries too low fat intakes may be a greater concern,leading several researchers to point out the possible dangers of dietary fat restriction for children.
Nevertheless, in a contra-point Lytle ⁷¹ defended a low-fat diet for healthy children and Van Horn ⁷² also reconfirmed the NCEP stand.
The Institute of Medicine in the most recent release of Dietary Reference Intake values seems to have accommodated both sides of the coin by formulating ‘Acceptable Macronutrient Distribution Ranges’ (AMDR), defined as ‘a range of intakes for a particular energy source that is associated with reduced risk of chronic disease while providing adequate intakes of essential nutrients’. ¹⁰
To address the nutritional excesses and deficiencies of South Africa, a land of contrasts, Vorster et al ⁷³ have also suggested that more specific guidelines be adopted, for example instead of advising that less than 30% of energy should come from fat, ranges, for example between 25% and 30%, or to aim for 30% should be considered.

DIETARY ASSESSMENT OF CHILDREN

Overview

Against the backdrop of evidence that many of the risk factors for the development of CNCD, for example nutrient intake,⁷⁴ obesity ²¹ and hypercholesterolaemia,⁷⁵ track from childhood into adulthood, dietary assessment of children is important in nutrition monitoring, research, and in clinical and community-based interventions.
Stang ⁷⁶ has compiled a practical overview of assessment of nutritional status in clinical practice, including dietary assessment, of adolescents. In the research context methods that can be used for dietary assessment range from very sophisticated individual-level investigations suitable for metabolic wards to ‘bird’s eye views’ aimed at describing diet on group level. Bingham ⁷⁷ has published a comprehensive review of the dietary assessment methods for use on individuals. Several overviews ^{30, 78, 79} focused their discussion on dietary assessment of children.
Apart from the general accuracy and precision issues of dietary evaluation,⁸⁰ studies in children pose additional challenges.^{79, 81} Three recent reviews emphasised the importance of establishing reliability and validity of dietary assessments specifically in children.^{25, 30, 81}
The duplicate portion technique has sometimes been described as giving very accurate information on the nutrient level. Isaksson ⁸² reviewed the principles involved. When total dietary fat and fatty acid intake measured by chemical analysis of duplicate diets were compared to nutritional database analysis of estimated dietary records, collected over the same three-day period, lack of agreement was found.⁸³
Unobtrusive observation in assessment of children’s dietary practices minimises self-report problems and has been considered as a ‘gold standard’ against which other measures of behaviour could be compared. The use thereof has been described by Baranowski and Simons-Morton.⁷⁹
The four methods most commonly used for assessing diets of individuals are the food record, the 24-hour recall, the food frequency questionnaire (FFQ) and the diet history. The first two methods describe current intake and are meal-based, whereas the latter two describe past or usual diet. All of these have been used in assessment of diets of children.^{25, 78} One of the major long-term studies involving children showed the feasibility of implementing a variety of dietary assessment methods among pre-adolescent children without relying primarily on parental reports, ⁸⁴ but for younger children parents are usually included either as surrogates or in addition to the child report.
New approaches, for example using the computer, telephones and tape recorders to record children’s food intake are being investigated.^{85, 86} Diet analysis tools are increasingly available online.⁸⁷
The FFQ and food record are discussed in more detail in later sections of this literature review.

Cognitive abilities of children affecting dietary assessment

Self-report of diet necessarily involves cognitive processes, although for many years limited research has focused on either adults’ ^{88, 89} or children’s ⁹⁰ cognitions in regard to food. Recently various research groups have started paying attention to this aspect.
It can be assumed that children in the four major periods of cognitive development (that is sensorimotor [birth to two years], pre-operational [two to seven years], concrete operation [seven to eleven years] and formal operations [eleven years and beyond]) differ in the way they process food information. The latter age is about the age from which children have been shown to provide reasonably accurate dietary information.
In order to systematically analyse the mental activities involved in food recall, Baranowski and Domel ⁹⁰ have proposed a model of a child’s cognitive processing of food information (Figure 2.1). This model is the result of combining cognitive psychology with survey methodology in order to optimise the collection of valid food intake data. In the model the recall of foods and the number of portions of such foods is addressed, primarily on the short-term. The cognitive skills involved in recalling frequency of intake (for example event equalisation, estimation of frequency, averaging) are not explicitly covered, but can be inferred. The model analogises human cognition to methods by which a computer processes, categorises, stores, and retrieves information. Apart from the implications for developing new dietary assessment tools, this model provides a starting point for categorising errors that can be encountered with children’s self-report of diet. As is evident from Figure 2.1, these errors can be related to attention, perception (or interpretation), organisation, retention, retrieval, and response (printed in italics in the Figure 2.1).
Noticing, that is paying attention to food eaten is a prerequisite for future recall. Inattentiveness may result in underreporting. The model also shows that paying attention to the request for dietary information is the critical starting point for valid recall. By increasing the interest in the task of remembering what was eaten, the quality of response can be improved.⁹⁰ Question comprehension is a critical cognitive stage in any dietary assessment involving recall. ⁹¹ In a FFQ it is essential that the participants understand the question and know how to report consumption frequency, portion sizes and compute average yearly use of seasonal items.
The foods consumed must be perceived by the child to be the same thing that the researcher meant. In their study involving fifth to seventh graders, Koehler et al ⁹² listed food knowledge, preparation and vocabulary as instrument-related factors influencing the validity of a dietary assessment tool. In this respect, the use of pictures has been shown to reduce misunderstanding. Picture-to-picture matching appears to be superior to picture-to-word matching, and pictures appear to trigger memory, where words have not.⁸⁸
Organisation, in the dietary recall context, refers to the grouping of foods in long-term memory. It may be that children classify foods differently to adults, for example by using functional criteria (that is meals versus snacks), nutritional or healthful criteria, or sweetness ⁹⁰ instead of, for example, the basic food groups. Furthermore, different children may organise foods differently, use different reasons for categorisations, and this may be affected by developmental stage. Baranowski et al ⁹⁰ and Koehler et al ⁹² reported that some children had difficulty understanding the wording of food categories on a food frequency form, for example when deciding in which category particular foods should be placed. Based on this rationale, some researchers (for example Kohlmeier ⁸⁸) have started rearranging their FFQ to a meal-based, rather than a list-based format.
Retention refers to memory and is related to time lapsed between the actual consumption and the request to recall the intake. In the case of children it was found that food memory decay varied by food group. However, underreporting appears to be more common than overreporting, even though this may, in part, be the result of researchers failing to differentiate between ‘underreporting’ (reporting one half of a banana when a whole banana was eaten) and ‘failure to report’ (reporting that no snack was eaten when in fact a banana was eaten).⁹⁰ Baxter and Thompson ⁹³ found that the cognitive burden of recalling items eaten at school lunch as part of a 24-h recall was greater than that of recalling school lunch items as single meal. Thus the latter yielded more accurate information. Even under the best conditions (for example reporting within 90 minutes after the meal) children have difficulties reporting their intakes.⁹⁴ This is, however, not unequivocally accepted: In a longitudinal study Dwyer and Coleman ⁹⁵ found that there was not necessarily a clear decline in accuracy of report over time when the same subjects were studied over four decades. Nevertheless, the distorting effect of current diet on recall of past food consumption was revealed.
The process of retrieval involves obtaining information out of long-term memory into short-term memory to form a response. In this stage interference can be a problem.⁹¹ As the time interval is increased over which diet must be recalled, interference will also be increased. It is unlikely that food information is stored separately, but it is probably embedded in other events.⁹⁰ This is why the use of event prompts (for example a party, sports event) can improve a 24-h recall. Domel ²⁹ explored how children remembered food intake and identified several memory retrieval-response categories, including visual imagery, usual practice, behaviour chaining, preference, food labels and so forth. The effect of different types of prompting on the accuracy of children’s food recalls has consequently been investigated.⁹⁶ These researchers found that among first grade students, specific prompting in terms of preference, food category or visual cues resulted in more harm that good. Among fourth-grade learners prompting for food categories resulted in some improvement in accuracy. When children report eating standard portion sizes rather than the real amount eaten, this can result in overreporting of low intakes and underreporting of high intakes, the so-called flat slope syndrome.⁹⁰ Prompting children to report foods eaten over the previous 24 hours in reverse versus forward order improved omission and intrusion rates of fourth-graders’ recalls, particularly for boys, but the overall error rate (omission plus intrusions) remained high.⁹⁷ Ensuring recognition of food items (either on a word-based list or on pictures), which is cognitively the core task in food frequency questionnaires,⁸⁹ aids the retrieval process.
Finally, response refers to the way in which children wish to present themselves to others. Social desirability plays a role here and was found to occur when children underreported candy consumption and over-reported vegetable consumption in a telephone recall compared to their parents’ reports.⁹⁰ If an event is considered as embarrassing, sensitive in nature, threatening or divergent from the respondent’s self-image, it is less likely to be reported.⁹¹
Thus, theoretically, memory and cognition are required for completing a FFQ, because participants must first recognise the food item. The consumption of each item must then be considered, the information over the reference period (for example one year) be integrated and finally the average frequency of food use computed. All of these processes are interlinked as indicated in Figure 2.1.
In practice Drewnowski ⁹⁸ has, however, argued that “reality is beside the point: FFQ’s reflect a long-established predisposition toward a mental image of a given food.” He thus implies that the cognitive processes are overemphasised and that in actual practice food preferences or attitudes are measured by FFQ and not ‘usual consumption’.

ABSTRACT
OPSOMMING
CHAPTER 1: RESEARCH PROBLEM IN CONTEXT
1.1 RATIONALE FOR STUDY: THEORETICAL CONTEXT
1.2 PRACTICAL CONTEXT
1.3 RESEARCH PROBLEM AND SUB-PROBLEMS
1.4 TERMINOLOGY
CHAPTER 2: REVIEW OF LITERATURE
2.1 NUTRITION OF PRIMARY SCHOOL CHILDREN
2.1.1 Eating habits of children
2.1.2 Dietary fats in childhood nutrition
2.2 DIETARY ASSESSMENT OF CHILDREN
2.2.1 Overview
2.2.2 Cognitive abilities of children affecting dietary assessment
2.2.3 Integrating nutrition and dietary assessment into the school environment
2.2.4 The food frequency questionnaire as basic format of the test method
2.2.4.1 Description
2.2.4.2 Aims
2.2.4.3 Strengths and limitations
2.2.4.4 Development of food frequency questionnaires
2.2.4.4.1 The item list
2.2.4.4.2 Quantification
2.2.4.5 Food frequency questionnaires for children
2.2.4.6 Food frequency questionnaires for fat intake
2.2.5 The food record
2.2.5.1 Description
2.2.5.2 Strengths and limitations.
2.2.5.4 The food record for children
2.3 NUTRITIONAL AND DIETARY SCREENING
2.3.1 Definition and characteristics
2.3.2 Aims
2.3.3 Examples of screeners
2.3.3.1 Fat screeners
2.4 RELIABILITY AND VALIDITY IN DIETARY ASSESSMENT AND SCREENING
2.4.1 Variability and error in dietary assessment
2.4.1.1 True variability
2.4.1.2 Error
2.4.2 Reliability
2.4.2.1 Definition
2.4.2.2 Types of reliability
2.4.2.3 Measurement of reliability
2.4.3 Validity
2.4.3.1 Definition and principles
2.4.3.2 Types of validity.
2.4.3.3 Validity of (dietary) screening tools.
2.4.4 Validation studies
2.4.4.1 Background
2.4.4.2 Validation studies in children
2.4.5 Factors influencing validity and reliability
2.4.6 Implications
CHAPTER 3:DEVELOPMENT AND DEVELOPMENTAL EVALUATION SUB-STUDIES OF RESEARCH TOOLS
3.1 TEST METHOD
3.2 REFERENCE METHODS
3.3 REFLECTION
CHAPTER 4: MAIN STUDY METHODS
4.1 SAMPLING
4.2 DATA COLLECTION
4.3 DATA PROCESSING AND ANALYSIS
CHAPTER 5: RESULTS
5.1 SAMPLE(S)
5.2 TEST METHOD
5.3 FOOD RECORD
5.4 SCREENER BY PARENTS
5.5 TRIANGULATION: TEST METHOD VERSUS FOOD RECORD VERSUS SCREENER BY PARENTS.
5.6 RECEIVER OPERATING CHARACTERISTICS
CHAPTER 6: DISCUSSION
6.1 DEVELOPMENT AND DEVELOPMENTAL EVALUATION SUB-STUDIES
6.2 MAIN STUDY: SAMPLE
6.3 TEST METHOD
6.4 REFERENCE METHODS
6.5 COMPARATIVE VALIDATION
CHAPTER 7: CONCLUSIONS AND RECOMMENDATIONS
REFERENCES
ADDENDA.
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