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Chapter 12 : Resistant Starch as a Prebiotic
Category: Clinical Microbiology
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Optimizing the large-bowel microbiota in terms of function and products has the potential to improve public and personal health. Prebiotics and probiotics have attracted considerable attention for their potential in this regard. This is despite the fact that there is abundant evidence that the composition of the gut microbiota and its metabolic activities are responsive to changes in diet. There are also technical difficulties of incorporating probiotic microorganisms into foods and maintaining their shelf stability. Recognition of these two obstacles has prompted interest in the concept of prebiotics, which recognizes that dietary factors, especially macronutrients, are prime determinants of the community structure and fermentation profile of the large bowel ecosystem. An understanding of the biology of dietary starches, their digestion in the upper gut, and their interaction with the microbiota of the large bowel is essential in ascertaining the full prebiotic potential of resistant starch (RS). The classification of RS into groups RS1 through RS5 and the widely diverse types that are consumed in foods show that it is very difficult to link consumption directly to prebiotic action. One of the obstacles to progress is the lack of an internationally accepted and validated analytical method for RS in human foods. The methodological limitations of culture techniques for enumerating bacteria are well documented. Quantitative molecular techniques (such as fluorescence in situ hybridization), being more specific, sensitive, and precise, allow more subtle changes in the microbiota to be detected.
Scanning electron micrographs of starch particles in commercially processed foods. (a) Commercial muesli containing multiple whole-grain cereals and other starch sources; (b) starch from commercial four-bean mix (canned). Bar, 10 µm.
Potential substrates for the colonic microbiota of adults on a Western dieta
Nutritional classification of RS