The Associations Between Dietary Anthocyanins, Cognitive Performance and Mood

<p dir="ltr">Flavonoids are a diverse class of dietary polyphenols comprising several subclasses, including flavonols, flavanones, flavan-3-ols, and anthocyanins. Anthocyanins are naturally occurring compounds responsible for the red, purple, and blue pigmentation in fruits and vegetables, and although they are typically consumed in relatively small quantities, they have distinct structural and biological properties that may influence neurocognitive processes. While other flavonoid subclasses have been extensively investigated in relation to cognitive outcomes, evidence specific to anthocyanins remains comparatively limited. Recent studies have advanced methods for assessing flavonoid intake, with emerging data suggesting potential neuroprotective effects of anthocyanins. To determine whether these associations can be translated into meaningful dietary strategies, further evidence is required to clarify their role in cognitive function and mood, particularly among populations at increased risk of age-related cognitive decline.</p><p dir="ltr">This thesis adopts a multi-method approach to address inconsistencies in the current clinical trials regarding anthocyanins and cognitive performance in adults. It also develops and validates a flavonoid-specific dietary assessment tool (FLAV-Q), explores associations between habitual anthocyanin consumption and cognitive outcomes, and assesses the feasibility of increasing anthocyanin intake through food-based interventions.</p><p dir="ltr">The thesis comprises four main components. First, a systematic review and meta-analysis of randomised controlled trials was conducted to evaluate the cognitive effects of anthocyanins. The review revealed suggestive benefits for cognitive and mood outcomes, but high study heterogeneity and methodological differences limited the ability to draw definitive conclusions.</p><p dir="ltr">Second, a shortened version of the Kent & Charlton Flavonoid Food Frequency Questionnaire (FLAV-Q) was developed and validated to rank flavonoid intake in the Australian population. While the tool demonstrated moderate to low validity for estimating absolute intake, it performed adequately in ranking individuals according to flavonoid intake and identifying key dietary sources, making it a practical tool for large-scale epidemiological studies but less so for clinical trials.</p><p dir="ltr">The third component involved a 24-week, multi-center randomised controlled trial with older adults (aged 60–85) experiencing self-reported memory complaints. Cross-sectional analysis of baseline data suggested a potential association between higher habitual anthocyanin intake and lower depressive symptoms, though no significant relationship with cognitive performance was observed. The subsequent trial which forms the fourth component included three arms: a diet intervention arm aiming to increase anthocyanin intake through dietary change, a supplement arm providing 250 mg/day of anthocyanins, and a control arm receiving a placebo. The diet intervention arm demonstrated that structured dietary counselling, combined with tailored educational materials (e.g., cookbook, shopping guide), successfully increased anthocyanin intake by an average of 114 mg/day. Although this fell short of the 250 mg/day target provided in the supplement arm, the results confirm the feasibility of food-based strategies to enhance anthocyanin intake in older adults.</p><p dir="ltr">This doctoral research makes several key contributions. It highlights the need for improved dietary assessment tools and calls for more rigorous studies to clarify the cognitive and mood-related effects of anthocyanins. It also addresses a critical gap in current dietary guidelines, which advocate fruit and vegetable intake but fail to recognize specific bioactive compounds like anthocyanins. The findings support the use of validated, flavonoid-focused dietary tools in future research and promote the integration of colourful, anthocyanin-rich foods into public health recommendations aimed at improving cognitive, mood and emotional well-being in ageing populations.</p>