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United States Department of Agriculture

Agricultural Research Service

Title: Dietary Fiber Decreases Metabolizable Energy Value and Nutrient Digestibility of Mixed Diets Fed to Humans

Authors
item Baer, David
item Rumpler, William
item Miles, Carolyn
item Fahey, G - UNIVERSITY OF ILLINOIS

Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 10, 1996
Publication Date: N/A

Interpretive Summary: Dietary energy and digestibility of foods in western diets can be affected by the content and type of dietary fiber. There are many analytical system for the measurement of dietary fiber but the physiological actions of fiber measured by different analytical methodologies have not been established. This study measured the metabolizable energy (ME) content of nine diets with different fat and fiber concentration and compared the digestibility of neutral detergent fiber (NDF) and total dietary fiber (TDF). Diets varied in level of fat (18%, 34%, or 47% of energy) and level of total dietary fiber (3%, 4%, or 7% of diet dry matter) and were consumed for 2 wk. Subjects (n=17) consumed three diets (14 d for each diet) containing different levels of fiber and one level of fat. Food consumption was measured and all urine and feces were collected during a 5 d period. Combustible energy, protein, fat, TDF, and NDF were measured in composite samples of food and feces, and urine was analyzed for combustible energy and nitrogen. ME and apparent digestibility coefficients were calculated. Overall, increasing fiber intake decreased fat and protein digestibility. As a consequence of these interactions, the ME content of the diets decreased as fiber intake increased, and TDF and NDF had similar effects on the ME value. A published empirical formula accurately predicted the ME content of diets using either TDF or NDF. These data are beneficial for regulatory agencies, food manufacturers and research scientists that are interested in predicting ME content of meals.

Technical Abstract: Food labeling regulations implemented by the United States Food and Drug Administration emphasize nutrient composition and energy content of foods. Dietary energy and digestibility of complex foods can be affected by the content and type of dietary fiber. The metabolizable energy value and apparent digestibility of dietary fiber in human diets is difficult to assess. Fiber can affect the digestibility of fat and protein and subsequently, the metabolizable energy (ME) value of the diet. This study was conducted to measure the ME content of nine diets with different fat and fiber contents. Diets contained one level of fat (18%, 34% or 47% of energy) and one level of total dietary fiber (3%, 4%, or 7% of diet dry matter) and were consumed for 2 wk. Subjects (n=17) consumed three diets (14 d for each diet) containing different levels of fiber and one level of fat. Food consumption was measured and all urine and feces were collected during a 5 d period. Combustible energy, protein, fat, total dietary fibe (TDF), and neutral detergent fiber (NDF) were measured in composite samples of food and feces, and urine was analyzed for combustible energy and nitrogen. Metabolizable energy and apparent digestibility coefficients were calculated. Overall, increasing fiber intake decreased fat and protein digestibility. As a consequence of these interactions, the ME content of the diets decreased as fiber intake increased, and TDF and NDF had similar effects on metabolizable energy availability. A published empirical formula was used to predict the ME content of diets using RDF or NDF. Both types of fiber adequately predicted ME content of these diets.

Last Modified: 4/23/2014