Pandey A, et al. - In this study involving 112 older patients with heart failure with preserved ejection fraction (HFpEF) and 37 healthy age-matched controls, researchers analyzed the status of vitamin D and its association with exercise capacity. For this investigation, they measured plasma 25-hydroxyvitamin D (25[OH]D) concentrations and exercise capacity (peak oxygen consumption [VO₂] and 6-minute walk distance) among study participants. They found that 25(OH)D concentrations in those with HFpEF were significantly lower vs healthy control participants. They also found that > 90% of patients with HFpEF had 25(OH)D insufficiency and 30% were frankly deficient. Lower 25(OH)D levels were related to lower peak VO₂ and 6-minute walk distance in patients with HFpEF, indicating that 25(OH)D insufficiency could contribute to exercise intolerance in this patient population.