Variation in the apparent faecal digestibility of macronutrients and urinary energy excretion for three diets varying in fat and fibre content-- assessment of the Atwater factors and related energy conversion factors : a thesis presented in partial fulfillment of the requirements for the degree of Master of Science in Nutritional Science at Massey University, Palmerston North, New Zealand
Loading...
Date
2007
DOI
Open Access Location
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Massey University
Rights
The Author
Abstract
Background: Current systems to estimate dietary metabolisable energy (ME), often based on Atwater factors, assume that diet ME can be accurately predicted based on a few chemical components and that the ME of components is constant across foods. Objective: Our aim was to investigate variation in apparent faecal nutrient digestibility and urinary energy excretion on different diets, and evaluate the accuracy of current systems for predicting dietary ME. Design: The ME contents of a refined (high fat, low fibre) diet and two high fibre low fat diets were determined in balance experiments on human subjects and calculated using factorial and empirical models. Apparent faecal nutrient digestibilities and urinary energy excretions were also determined. Results: The difference between calculated (Atwater factors) and determined ME values was up to 4% for the refined diet and 11% for the high fibre diets. The empirical models were generally no more accurate than the modified Atwater factorial model. Apparent faecal nutrient digestibility varied considerably among the three diets, as did urinary energy per unit urinary nitrogen. Mean digestibilities ranged from 81.4 (fruit and vegetable diet) to 90.0% (refined diet) for crude protein; 87.0 (fruit and vegetable diet) to 95.7% (refined diet) for fat; 91.1 (cereal diet) to 95.5% (fruit and vegetable diet) for total carbohydrate. Mean urinary energy per unit urinary nitrogen ranged from 33.9 (refined diet) to 44.1 KJ/gN (fruit and vegetable diet). Conclusion: Modified Atwater factors and some of the empirical models evaluated here may be suitably accurate (±5%) for use for general food labelling purposes and for determining dietary ME intakes of groups and populations, but may be inadequate for application to specialised weight-loss diets and ingredients. KEY WORDS Atwater factors, Digestibility, Energy, Metabolisable Energy, Urinary Energy Excretion.
Description
Keywords
Food -- Caloric content, Digestion