Abstract
Cardiovascular disease (CVD) is the leading cause of mortality and morbidity in the UK and other Westernised countries. High dietary intakes of whole grains have been associated with a reduced risk of CVD and other associated morbidities including obesity and type II diabetes. The evidence, however, is predominantly observational, with very few randomised controlled dietary intervention studies, and thus can not be used to suggest a causative role for whole grains. The aim of this research, therefore, was to investigate the effects of whole grains and their components and metabolites on markers of endothelial dysfunction and cardiovascular risk both in vivo and in vitro using a variety of approaches. It was hypothesised that an increase in whole grains and their constituents would reduce CVD risk as reflected in the markers investigated. The Pilot Whole grain Intervention Study in England (Pilot WISE) trial was a randomised controlled parallel dietary intervention which investigated the effects of 48g whole grain per day on CVD risk markers and circulating metabolite profiles of men and women (aged 48.4 +/- 11.7 years, BMI 28.8 +/- 3.1kg/m2) over eight weeks. The Fibre and Inulin Trial in Male Adults (FITMA) trial, a randomised controlled cross over designed dietary intervention trial researched the impacts on such CVD risk markers and metabolite profiles of 15g/day wheat fibre or inulin in high risk men (aged 39.8 +/- 3.0 years, BMI 30.2 +/- 1.0kg/m2, n= 10) over 28 days. The effects of a range of physiologically relevant concentrations of the fermentation products of whole grains, the short chain fatty acids (SCFA), on cellular models of the vascular endothelium were also investigated to explore the potential mechanisms behind the proposed risk reduction. Dietary interventions of whole intact and whole milled grains, wheat fibre or inulin did not significantly impact on circulating levels of inflammatory or haemostatic markers, lipid profiles or markers of insulin sensitivity. Circulating levels of three species of lysophosphatidylcholines, however, were significantly altered by the wheat fibre and inulin in the metabolic profile analyses. Treatment of endothelial cells with SCFA did not significantly alter levels of secreted inflammatory or haemostatic mediators or of cellular adhesion molecules. In conclusion, no beneficial effects were observed as a consequence of the diets high in whole grains or their components and, as such, these data can not be used to support the dietary health messages associated with high whole grain intakes. Future work could benefit from involving higher numbers of participants or those with a higher CVD risk profile at baseline.