The efficacy of dry beans (Phaseolus vulgaris L.) for improving vascular function: exploring seed coat colour as an indicator of functionality
Consuming pulses over several weeks improves vascular function and decreases cardiovascular disease risk; however, it is unknown whether pulses can positively modulate postprandial vascular responses, a delimiting factor in projecting vascular health. Bioactive compounds within pulses are the suggested effectors; thus, dry beans (Phaseolus vulgaris L.) were investigated due to their contrasting seed coat colours, indicative of distinct phytochemical profiles. A randomized crossover study investigated the effects of beans with different seed coat colours (white, tan, red, and black) on postprandial vascular and metabolic responses in healthy adults. Darker-coloured beans induced positive postprandial vascular responses, as evidenced by blood vessel relaxation within six hours of consumption. Additionally, the different beans elicited distinct responses for various vascular and metabolic parameters depending on seed coat colour. Thus, bioactive compounds unique to each bean type are likely responsible for the different biological effects. To investigate potential vasorelaxation mechanisms, serum samples were analyzed by untargetted metabolomics to identify novel endogenous metabolites that changed following consumption of the different bean types. Darker-coloured beans altered 47 metabolites within six hours that were unchanged by lighter-coloured beans. Circulating acylcarnitines were tentatively identified as compounds of interest because they are linked to improved blood flow, but absolute identities were not confirmed. The chronic effects of navy and black beans on vascular structure and function were investigated in spontaneously hypertensive rats, a model of essential hypertension. Black beans, but not navy beans, improved vascular compliance of mesenteric resistance arteries, but this was reversed when bean consumption ceased for 4 weeks. These findings indicate that regular consumption of black beans was required to retain the positive effects on the vasculature. In summary, darker-coloured beans improved vascular function in healthy individuals and hypertensive animals. The findings indicate that bean seed coat colour may be a visual marker for the vascular effects of beans. Although a mechanism of action was not elucidated, darker-coloured beans modulated the endogenous metabolome and this provides opportunity for further exploration of mechanism. Overall, this research provides evidence for including darker-coloured beans regularly in the diet as a strategy to maintain blood vessel health.
Beans, Black beans, Red kidney beans, Pinto beans, Navy beans, Vasorelaxation, Hypertension, Arterial stiffness, Metabolomics