| Summary: | Cardiovascular diseases (CVD) remain one of the leading causes of death in the world. Despite the decreasing incidence of CVD in Western countries, due to the aging population, the prevalence is still increasing. High blood pressure (BP) is the most important modifiable risk factor for CVD, due to its high mortality rate. The impact of diet on CVD and its risk factors is well described. Epidemiological studies have demonstrated an inverse association between high milk consumption and lower BP. Milk is a complex, nutrient-dense food containing an array of essential nutrients. It is, however, of great scientific interest to determine which constituent is responsible for this beneficial effect. Milk proteins have been shown to exert angiotensin-converting enzyme inhibitory (ACEi) effect, which is a key enzyme in BP regulation. After an extensive literature search, a meta-analysis was performed to examine the impact of the casein-derived lactotripeptides on BP. This study demonstrated hypotensive effects in humans, specifically in Japanese individuals. A clear gap in the current scientific knowledge was well-designed randomised controlled trials to examine the effects of intact milk proteins on BP and other novel and classic risk markers for CVD. The findings from my randomised, controlled, double-blind, chronic intervention study showed that whey protein consumption (2 x 28 gld) for 8 weeks reduced 24-h ambulatory BP, peripheral and central BP assessed by applanation tonometry as well as improved endothelial function (flow-mediated dilation› FMD) compared to control (2 x 27 gld maltodextrin) in 38 hypertensive participants. Whey protein also reduced fasted total cholesterol (TC) and triacylglycerol (TAG) compared with control, while Ca-caseinate (2 x 28 glday) improved endothelial function (FMD) and lowered fasted TC compared with control. Both whey protein and Ca-caseinate decreased adhesion molecules compared to control (sICAM-l was decreased by whey protein and VCAM-l by Ca-caseinate). These changes were achieved without significant changes in body weight or habitual diet of the participants. The acute study also demonstrated beneficial effects of dairy proteins after two high-fat meal challenges in 27 mildly hypertensive adults: whey protein (28 glmeal) decreased BP between the two test meals compared with Ca-caseinate (28 glmeal) and control (27 glmeal), and also improved arterial stiffness (augmentation index) and maintained endothelial function (FMD) over the 8-h postprandial period. Furthermore, although whey protein increased insulin response to a similar magnitude to the carbohydrate-based control, lower postprandial glycaemia was maintained by whey protein. Furthermore, Ca-caseinate lowered postprandial TAG response compared with whey protein. The purported molecular mechanisms underlying the impacts of dairy proteins on the cardiovascular system still remain unclear. The in vitro ACEi experiment presented in this thesis confirmed the hypotensive effects of whey protein over Ca-caseinate and control, however serum samples failed to confirm this ACEi activity. In summary, milk proteins, particularly whey protein, had important fasted and postprandial benefits to the cardiovascular system compared with control, however concomitant consumption of dairy proteins may be of further benefit due to their different kinetics in the gastrointestinal system. Future research should address the impacts of milk proteins in type 2 diabetic patients with impaired glucose metabolism .
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