Modulation of fat digestion using bioactive alginates

PhD ThesisObesity is a fast growing medical issue worldwide and is one of the leading causes of mortality. There is evidence to suggest that various forms of dietary fibre may be used in weight management and for their general health benefits. There is evidence to suggest that the addition of alginate to a food or beverage has the potential to alter the digestion process and potentially reduce the activity of digestive enzymes. Data from this laboratory have demonstrated that alginate possesses the ability to inhibit pancreatic lipase in-vitro. Pancreatic lipase is secreted in the small intestine and hydrolyses fat so that it can be absorbed in the digestive system. If the activity of pancreatic lipase can be reduced then the amount of fat absorbed will be reduced. A modified Periodic Acid Schiffs (PAS) assay is an effective, repeatable and simple method for quantifying alginate in solution. Furthermore with any potential weight loss treatment the release rate must be determined. The model gut system developed in this laboratory is able to digest the alginate enriched bread and the modified PAS assay system is able to quantify the release rate of the alginate, with between 12-20% released in the gastric phase and 80-88% released in the small intestinal phase. The data here also confirms that the bread is protecting the alginate during the cooking process, and that the alginate retains its inhibition properties despite the cooking and digestion process. The model gut is an effective model for digesting fat substrates and foods high in fat such as butter and olive oil. Alginate enriched bread has the ability to inhibit fat substrates glyceryl trioleate, trioctanoate, tributyrate, and foods butter and olive oil 62, 39 and 32, 95 and 78% respectively after 180 minutes in the model gut. Alginate enriched bread is able to modulate fat digestion in ileostomy subjects following ingestion. This was evident by a significant increase in fat content of the effluent fluid. There was an increase in fat content of 81g and 112g when subjects consumed alginate bread when compared with control bread at 240-270-300 minutes and when total fat was combined for all time points respectively. There was also an increase of 292g in wet effluent weight for alginate bread when compared with the control bread. In addition a significant relationship between the wet effluent weight and fat content of the effluent was reported. The alginate enriched bread had no problems with palatability or adverse side effects associated with fat digestion and suggest that alginate enriched bread may be a suitable method for the delivery of alginate into a normal diet. The data in this thesis suggests that alginate enriched products are able to attenuate the digestion of fat and therefore may be used in weight management and in the treatment of obesity, however further longitudinal clinical research is required in a healthy population before any health claims can be made