Cheese see Dairy Products

2 weeks 1 year 7 years 15 years

Figure 1 Changes in protein and energy requirements during infancy and childhood.

115 kcal

95 kcal

Energy- kcal per kg body weight

Protein- g per kg body weight

75 kcal

45 kcal

0.9 g bioavailability of nutrients are quite different between breast milk and infant formula. In addition, breast milk composition changes during the duration of a feed and it is difficult to estimate the usual volumes of breast milk consumed. Dietary reference values are therefore only applicable to artificially fed infants: An adequate quantity of breast milk is assumed to meet all nutrient requirements for the majority of infants up until the age of approximately 6 months.

Estimates of physiological requirements are used to make dietary recommendations, which depend on the usual diet of the country or area. Again, estimates cannot be 'scaled down' versions of adult requirements because bioavailability of many nutrients varies with age, physiological state, and nutritional status. For example, iron absorption is poor during the first 6 months of life, increases during later infancy, and is greatest during adolescence.

Requirements for children are estimated from a limited number of direct studies of body composition and body content of children at different ages. Most of these were carried out on children living in unfavorable environments and very little data exist on normally nourished children, particularly those aged between 1 and 5 years. Recommendations are often extrapolated from adult studies. For most nutrients, energy and protein requirements are not known with any great precision and are expressed as units per day.

Discrepancies between recommendations published by different countries or authorities are due to a number of factors: Different assumptions are made about weight at a particular age, growth velocity, and age of onset of puberty, and different age groupings are used by different authorities. Some countries give recommendations for each year of life, whereas others aggregate several years together, giving an overestimation for the youngest ages and underestimation for older children in each age band. Some countries separate recommendations for males and females as early as the second year; others separate them at a later age or only during adolescence. Table 1 illustrates the framework on which different recommendations and reference values are based. Diets of varying composition will affect bioavailability and, as a consequence, recommendations for dietary intake. Therefore, it is difficult to compare recommendations from different authorities and very large discrepancies exist in recommendations for some nutrients.

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