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Title: Whole-grains : prebiotic potential and effects on immune function, inflammation and glucose metabolism
Author: Ampatzogloll, Antonis
Awarding Body: University of Reading
Current Institution: University of Reading
Date of Award: 2013
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Consumption of whole-grains (WGs) is associated with a wide range of health benefits, but clinical data regarding effects of wG consumption on blood lipids, glucose metabolism, inflammation and immune function is either conflicting or limited. There is also a lack of information on how cereal type and processing may influence the prebiotic potential and health effects of WGs. The work described in this thesis combined a human intervention study of WO and an ill vitro investigation of the effect of processing and cereal type on fermentation properties of WOs. Habitual 10w consumers of wG (< 24 g/d) participated in a randomised crossover study with a diet high in WG (> 80 g/d) or low in WG (< 16 g/d), with intervention periods of 6 weeks, separated by a 4-week washout. Adherence to the dietary regimes was achieved by specific dietary advice and provision of a range of food products and verified with food diaries and plasma alkylresorcinols (ARs). In the ill vitro studies, cereal samples and functions were fermented in anaerobic pH-controlled faecal batch cultures and bacterial concentrations and diversity and short chain fatty acid concentrations were analysed. On the WG intervention, consumption increased on average to 168 g/d (P < 0.(01), accompanied by a significant increase in ARs (P < 0.001) and fibre intake (P < 0.001), without any effect on intake of energy or macronutrients. However, there were no effects on body composition, blood pressure, blood lipids, gut microbiology, immune system or markers of inflammation or glucose metabolism. Nevertheless, during the WO period, there were trends for higher 24 h faecal weight and lower body weight and BMI, and trends for alterations in some immune, inflammatory and metabolic markers. In the ill vitro fermentation studies, all samples and fractions altered bacterial diversity, but maize and unprocessed flour were the most bifidogenic of the cereal samples and processing conditions, while refined samples resulted in greater increases in lactobacilli. Of the cereal fractions, fructan exhibited the greatest bifidogenic effect, while β-glucan resulted in the greatest increase in propionic acid. This study demonstrates that a significant increase in WG consumption in habitual low-consumers had little effect on parameters of gut, immune and metabolic health. Cereals differ significantly in their ill vitro prebiotic potential, and this is influenced by the degree and type of processing, which may underlie the lack of effect in the intervention stud y..
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available