UNit6儿童营养 Nutritional requirements ofchildern.docx

1、UNit6 儿童营养 Nutritional requirements ofchildernUnit 4 Nutrition, health and schoolchildrenOver the last 50 years, there has been a change in the predominant concerns about the diets and health of school aged children. Historically, the focus has been on the provision of sufficient nutrients and energ

2、y in relation to current and future needs, but providing dietary balance and encouraging less sedentary lifestyles are now viewed as the main priorities .Personal, Social and Health Education programmes of study, together with other government initiatives such as the Wired for Health website, the Sc

3、hool Fruit Scheme will contribute towards empowering children with knowledge and opportunities to make informed choices for their future health.Text A Nutritional requirements of childrenDietary reference valuesIt has long been recognized that good nutrition is of crucial importance for the well-bei

4、ng, growth and development of children. Even though the energy cost of growth is a minor component of total energy requirements, growth rate is a sensitive indicator of overall dietary adequacy. In the longer term, food patterns in childhood, particularly adolescence, can set the scene for future di

5、etary preferences and eating behavior in adult life. There is also substantial evidence that poor diet and poor physical activity patterns in childhood can store up problems that manifest later in life, particularly in relation to heart disease, obesity, type 2 diabetes and some forms of cancer.The

6、nutritional requirements of children are high in relation to their size because of the demands for growth, in addition to requirements for maintenance and physical activity. Early puberty will also affect nutritional requirements.Tables 1 and 2 show the UK Dietary Reference Values (DRV) for energy a

7、nd selected nutrients for children from 4 to 18 years. These are used as a guide to the adequacy of childrens diets. The estimates of requirements for protein, vitamins and minerals for groups of children are expressed as Reference Nutrient Intakes (RNI), the RNI being the amount that is sufficient

8、for almost all (97.5%) individuals. The Estimated Average Requirement (EAR) is used as an indication of energy requirements, and by definition 50% of people in a defined group will need less than this to maintain energy balance and 50% will need more. The energy EAR assumes a sedentary lifestyle (as

9、 this is the situation for the majority of people in Britain, though increased activity is advised); use of the RNI (equivalent to the mean plus 2 standard deviations) would mean that predicted intakes would be greater than most peoples needs and hence would result in weight gain over a period of ti

10、me. Because of insufficient data, at the time the DRVs were set, from UK studies measuring actual energy expenditure in children aged 410 years, the estimated average requirements for energy by different age and gender groups have been based on intake data from a number of studies conducted in healt

11、hy well-nourished children in the UK and elsewhere The energy requirements for older children 1118 years, however, are based on energy expenditure data, expressed as multiples of basal metabolic rate.Table 1 Dietary Reference Values for boys aged 418 yearsAge (years) Units 46 710 1114 1518Energy MJ

12、7.16 8.24 9.27 11.51Kcal 1715 1970 2200 2755Protein g 19.7 28.3 42.1 55.2Iron mg 6.1 8.7 11.3 11.3 Calcium mg 450 550 1000 1000Zinc mg 6.5 7.0 9.0 9.5Magnesium mg 120 200 280 300Phosphorus mg 350 450 775 775Sodium mg 700 1200 1600 1600Vitamin A mg 500 500 600 700Vitamin B1, thiamin mg 0.7 0.7 0.9 1.

13、1Vitamin B2, riboflavin mg 0.8 1.0 1.2 1.3Niacin mg 11 12 15 18Vitamin B6 mg 0.9 1.0 1.2 1.5Vitamin B12 mg 0.8 1.0 1.2 1.5Folate mg 100 150 200 200Vitamin C mg 30 30 35 40Recommendations for the population in general, i.e. all agesFat % food energy 35of which saturates % food energy 11Carbohydrate %

14、 food energy 50of which starch, intrinsic sugars and milk sugars % food energy 39of which NME sugars* % food energy 11Source: Department of Health 1991. *Non-milk extrinsic sugars.Table 2 Dietary Reference Values for girls aged 418 yearsAge (years) Units 46 710 1114 1518Energy MJ 6.46 7.28 7.92 8.83

15、Kcal 1545 1940 1845 2110Protein g 19.7 28.3 41.2 45.0Iron mg 6.1 8.7 14.8 14.8Calcium mg 450 550 800 800Zinc mg 6.5 7.0 9.0 7.0Magnesium mg 120 200 280 300Phosphorous mg 350 450 625 625Sodium mg 700 1200 1600 1600Vitamin A mg 500 500 600 600Vitamin B1, thiamin mg 0.7 0.7 0.7 0.8Vitamin B2, riboflavi

16、n mg 0.8 1.0 1.1 1.1Niacin mg 11 12 12 14Vitamin B6 mg 0.9 1.0 1.0 1.2Vitamin B12 mg 0.8 1.0 1.2 1.5Folate mg 100 150 200 200Vitamin C mg 30 30 35 40Recommendations for the population in general, i.e. all agesFat % food energy 35of which saturates % food energy 11Carbohydrate % food energy 50of whic

17、h starch, intrinsic sugars and milk sugars% food energy 39of which NME sugars* % food energy 11Source: Department of Health 1991. *Non-milk extrinsic sugars.Since the 1985 FAO/WHO/UNU（ Food and Agriculture Organization/World Health Organization/United National University)report, more has been learnt

18、 about the energy expenditure of children and adolescents, and the distribution of time spent in activities of differing levels of energy expenditure, largely as a result of the application of the doubly labeled water method and other techniques such as heart rate monitoring (Torun et al. 1996). Tor

19、un et al. have reviewed the available data and published recommendations for research priorities, designed to help provide a more complete picture of childrens energy needs. They highlight the importance of coupling dietary energy guidelines with strong recommendations on physical activity, noting t

20、hat the minimum amount of activity compatible with good health in childhood has not been precisely determined. A review of energy requirements is currently being undertaken by FAO and others.Desirable intakes of carbohydrates and fats are expressed as a proportion of total dietary energy. These take

21、 into account eating habits in the UK and the practical implications of achieving change in line with what is considered desirable for health. They have been calculated with the needs of the adult population in mind. Whilst these values provide a useful guide for older (school age) children, they sh

22、ould not be applied rigorously to the diets of pre-school children.There are no specific estimates for the desirable amount of fibre (non-starch polysaccharide, NSP) for children. The Department of Health (1991) recommends that children should have proportionally lower fibre intakes than adults; the

23、 DRV for adults is 18 g of NSP per day. It should be noted that recently the Food Standards Agency has announced that different methodology (the American Association of Analytical Chemists (AOAC) method rather than the Englyst method) is to be used to assess the dietary fibre content of foods; this

24、change will necessitate reassessment of the DRV figure as the two methods are not comparable.For most essential nutrients, requirements have been estimated by extrapolating from published data for infants and adults, as little specific information for school aged children exists. During adolescence,

25、 nutrient requirements are set higher for boys than for girls because of their increased rates of growth, bone synthesis and bone mineralisation. Once menarche is reached and periods start, girls lose on average the equivalent of 12.5 mmol (1 mmol = 55.9 mg) of iron per day, although there is wide v

26、ariation in the amount of blood lost, with girls on the 95th cantle losing around 34 mmol per day. These data have been used to set the iron requirements for girls at a level higher than for boys and much higher than during the prepubertal period.Similarly, there are no estimated requirements for vi

27、tamin D because it is expected that, with the exception of very young and very elderly people, most people obtain an adequate amount of the vitamin via the action of sunlight on the skin. However, it has become apparent that a substantial proportion of children have low vitamin D status and this may

28、 carry public health implications . There is little evidence to suggest different requirements among ethnic groups, although the Department of Health (1980) continues to recommend that all Asian children take vitamin D supplements as a precaution, particularly where religion and customs dictate that

29、 their skin is kept covered outside, resulting in a reduced exposure of their darker skin to the relatively weak sunlight available in the UK.Fluid requirementsFluid requirements are an often overlooked aspect of diet. To replace fluid losses, which occur via urine, sweat and breath, 1.5 mL per kcal

30、 expended has been recommended as a total fluid requirement. This amounts to a total fluid intake of approximately 2600 mL per day for a 7-year-old girl and 4000 mL per day for a 15-year-old boy. However, allowances need to be made for the fluid content of foods included in the diet. It is now gener

31、ally accepted that 68 glasses of fluid per day (appropriate for the size and age of the child) should be sufficient, although more will be needed in hot weather and after vigorous physical activity. In adults, thirst is a good indicator of fluid needs, if responded to promptly. However, children may

32、 need to be encouraged to drink sufficient to rehydrate, e.g. after exercise, and provision of flavored water is often more acceptable. If lost fluid is not replaced, dehydration will result. In the short term, poor hydration causes headaches, continence problems and constipation, but in the longer term can lead to urinary tract infections, kidney stones and kidney disease. There is also anecdotal evidence that alertness and cognitive performance can be compromised by