Dietary anthocyanins and cardiovascular risk factors: the influence of tart Montmorency cherries on health indices in middle-aged adults

Anthocyanins, the subclass of polyphenol flavonoids responsible for the red-blue-purple pigmentation of fruit and vegetables, have gained much research focus recently due to their propensity to preserve or even improve vascular function. There is some evidence that higher-intake of foods rich in these compounds can positively impact risk factors associated with (CVD) cardiovascular disease such as blood pressure, endothelial function and arterial stiffness; albeit ambiguity remains as to whether this translates to a reduced risk of CVD. One of the most studied anthocyanin-rich foods in recent years has been tart Montmorency cherries (Prunus Cerasus, cv Montmorency; MC), particularly in exercise and to a lesser extent in health paradigms. Indeed, cherries can contribute to a considerable dietary intake of anthocyanins, but they are also a rich source of other polyphenols, which might confer health benefits due to the synergistic and additive properties on antioxidant or anti-inflammatory actions. Certainly, there is some promising evidence from in vitro and animal models that MC can influence pathways that might improve cardiovascular and metabolic health. Moreover, accumulating evidence has shown that acute postprandial exposure to MC, potentially due to its anthocyanin content, effects vascular and metabolic function in humans. Despite this there is a paucity of original research relating to the longer-term influence on cardiovascular function, and health in general. Moreover, existing studies are difficult to interpret due to limitations and the paradoxical findings, highlighting the need for well-designed clinical trials investigating MC on cardiovascular risk factors. Taken all together, the overarching aim of this thesis, was to further investigate the potential role of dietary anthocyanins in cardiovascular health. The reliability of a test battery of cardiovascular risk factors was also assessed, leading to three experimental studies (Chapter 3-5). Firstly, a systematic literature review evaluated the current evidence for the association between dietary anthocyanin intake and risk of CVD. In the largest and most comprehensive meta-analysis of existing prospective cohort studies, it was found that a higher intake of anthocyanins reduced risk of both coronary heart disease (CHD) and CVD mortality. These data further support the notion that exposure to anthocyanins could have a putative role in cardiovascular health, but clinical trials are still needed to verify these findings. Nonetheless, as a prelude to a randomised controlled trial, Chapter 4 investigated the repeatability of a battery of vascular function test measures. The repeatability of blood pressure, arterial stiffness and macro-vascular endothelial function was found to be adequate and this was used to inform the final study. Chapter 5 reports the influence of anthocyanin-rich MC on physiological or cognitive function in middle-aged adults. This randomised, double-blind, placebo-controlled trial had several strengths such that it was successfully blinded, relatively large sample size, longer-term supplementation period and well controlled compared to other studies of a similar nature. However, the results suggested no influence of MC juice on vascular function, metabolic health, cognitive function, or exercise capacity after three months in middle-aged adults. There was an effect on mental fatigue and alertness visual analogue scales (VAS) during the cognitive function test battery, suggesting an anti-fatiguing effect of MC. Moreover, Chapter 6 outlines important limitations and future research directions, that will help strengthen the evidence base regarding the intake of anthocyanin-rich foods and CVD. Collectively, these studies have contributed to knowledge on longer-term exposure to dietary anthocyanins and how they can impact on indices associated with health outcomes in humans