It is well accepted that dietary fibres, especially mixed linkage (1→3, 1→4)-β-Dglucans (β-glucan) from barley and oat, have beneficial effects on health and prevent modern lifestyle diseases. Even though recent research has shed some light on the mechanisms of action and structure-functionality relationship of β-glucans, the exact functional principle remain elusive. The overall aim of this project was to provide new knowledge into the relation between β-glucan and health at a molecular level.
For the first time two barley and one oat fractions of well-defined and structurally different β-glucans were compared in a human intervention study. The work first focussed on large-scale extraction and physico-chemical characterisation of barley and oat β-glucans. The second step was to investigate the in vitro health effects of barley and oat β-glucans in relation to their physico-chemical properties. Finally, health effects from barley and oat β-glucans were studied in vivo in humans using traditional biomarkers and plasma metabolomics.
Results from Papers I demonstrated that structural characteristics and viscous properties of barley and oat β-glucans dominate the functional traits over the presence of α-glucan impurities. Paper II identified a structurally unique barley high β-glucan variety with an extraordinary high amount of cellotriosyl units and showed that the oligomer block structure of barley and oat β-glucans influence their solubility. The main findings from Papers III and IV in vitro studies were that small molecule interaction with barley and oat β-glucans is influenced by degree of polymerisation and β-glucan fine structure whereas β-glucan solubility and aggregation are key elements for understanding their immune modulating capacity.
Results from the Paper V in vivo human study showed that consumption of 3.3 g/day extracted barley and oat β-glucan for 3 weeks does not significantly lower total and LDL cholesterol levels in young and healthy adults. However, an indicated potential effect of oat suggests the importance of solubility for β-glucan interference with the cholesterol metabolism. The findings from Paper VI confirmed the general absence of barley and oat β-glucan effect on blood metabolites but showed the existence of subject unique lipoprotein profiles depended on gender, BMI and diet.
In conclusion, the results show that barley and oat β-glucan fine structures are of great importance for their functionality. β-Glucan solubility and polymer aggregation in solution is dependent on the block structural pattern and differently structured β-glucans may exert various functional and bioactive properties in our body. It is important to account for these diverse effects in the future evaluation of β-glucan effectiveness in functional foods and health.