Cocoa flavanols alleviate early diastolic dysfunction by decreasing left atrial volume in a randomized double blinded trial in healthy older individuals

<i>Aims</i>: Left atrial (LA) enlargement marks impaired cardiac filling and predicts future cardiovascular events. Dietary flavanols have been shown to reduce cardiovascular mortality, despite uncertain underlying mechanisms. In this study, we hypothesized that flavanol intake reduces LA volume in older individuals without cardiovascular diseases. <i>Methods</i>: In a substudy of the randomized, double-blinded Healthy Aging Through Dietary Intervention trial (NCT05782309), we investigated the effects of cocoa flavanols on cardiac volumetry and diastolic function in healthy older individuals. LA and left-ventricular (LV) volumes as well as strain rates were measured by high-resolution cardiac magnetic resonance imaging before and after flavanol intake. <i>Results</i>: Sixty-three participants (59% male) aged ≥ 55 years received either 500 mg cocoa flavanols (containing 80 mg (-)-epicatechin) originating from cocoa extract (<i>n</i> = 30) or a control (<i>n</i> = 33) twice daily for 30 days. Flavanol intake counteracted subclinical cardiac dysfunction, evidenced by a 12.6 ± 3.5% reduction in maximal LA volume (<i>p</i> = 0.0063) and LA volume index (<i>p</i> = 0.0067) and ∼4.4 ± 1.9% reduction in LV end-diastolic volume (LVEDV) (<i>p</i> = 0.049) and LVEDV index (<i>p</i> = 0.041). Flavanol intake did not influence strain, strain rate, and systolic function parameters, while the systolic blood pressure decreased by 7 mmHg [∼4.7 ± 1.9% (<i>p</i> = 0.04)]. Blood pressure dynamics, gender or age of participants in the intervention group were not associated with LA volumetric changes. <i>Conclusion</i>: We provide evidence that cocoa flavanol intake mitigates early changes of diastolic dysfunction by reversing left atrial and left ventricular remodeling, thus providing novel insights into the mechanisms behind the beneficial cardiovascular effect of flavanol intake. The clinical trial registry number is NCT05782309 (https://clinicaltrials.gov).