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close this bookActivity, Energy Expenditure and Energy Requirements of Infants and Children (International Dietary Energy Consultative Group - IDECG, 1989, 412 pages)
close this folderThe energy requirements of growth and catch-up growth
close this folder8. Extent to which colonic fermentation of carbohydrates contributes to energy requirements in childhood
View the document8.1. Colonic fermentation
View the document8.2. Energy from SCFA
View the document8.3. Factors influencing SCFA production
View the document8.4. Gross versus metabolizable energy
View the document8.5. Faecal energy and non-starch polysaccharide
View the document8.6. Faecal energy in cystic fibrosis

8.4. Gross versus metabolizable energy

Further support for the role that colonic fermentation may play in meeting the energy needs of the individual comes from balance studies in which the true metabolizable energy intake (gross intake minus faecal and urinary losses) has been compared with the metabolizable energy intake estimated from food composition tables. There are several approaches in use for calculating the metabolizable energy content of mixed diets from the foods and the nutrients they contain. In 1899, ATWATER and BRYANT published factors that could be applied to the protein (4 kcal/g), fat (9 kcal/g) and carbohydrate (4 kcal/g) content of different foods based upon balance experiments in human subjects. The factors were subsequently modified by MERRILL and WATT (1973) who stated that if the revised factors were used, the deviation between the true and calculated metabolizable energy intake would not exceed 5% of the true value for most diets. In the United Kingdom, a slightly different approach has been used (PAUL and SOUTHGATE, 1978). The methods differ in the approach adopted for the calculation of metabolizable energy from carbohydrate. Paul and Southgate gave the metabolizable energy as 'available carbohydrate' (effectively excluding NSP) x 3.75 kcal/g. In contrast, MERRILL and WATT (1973) used a range of values, 3.87 to 4.12 kcal/g for carbohydrate. Using the first approach, SOUTHGATE and DURNIN (1970) found that the contribution of dietary NSP to metabolizable energy could be disregarded on diets containing low levels of NSP, up to 32 g/d.

GĂ–RANZON and FORSUM (1986) showed that when the potential contribution made by dietary fibre (NSP) was excluded there was a consistent underestimation of the metabolizable energy for diets high in dietary fibre. They calculated that dietary fibre, derived mainly from cereals, would contribute 10 kJ (2.5 kcal)/g to metabolizable energy. The dietary fibre from beans, vegetables and fruits would provide 13 kJ (3.1 kcal)/g. These values are in general agreement with the findings from studies in ruminants where approximately 70-75% of the heat of combustion of NSP may be available for metabolism (WHISKER, MALTZ and FELDHEIM, 1988). If these figures are applicable in humans, the energy available from dietary fibre would be a maximum of 13 kJ (3.1 kcal)/g (CUMMINGS, 1981).