Vitamin D supplementation and forearm vascular function in postmenopausal females

Introduction: Vitamin D deficiency (VDD) affects 24-40% of people in Western countries and poses a significant public health concern. Vitamin D plays a role in vascular regulation, and VDD is associated with cardiovascular diseases (CVD). Notably, females are at higher risk of CVD after menopause and vascular dysfunction is an early predictor of CVD. Forearm blood flow (FBF) and vascular conductance (FVC) can serve as indicators of vascular health; however, whether Vitamin D supplementation influences FBF and FVC in postmenopausal females – potentially contributing to CVD risk in this population – is unclear. Purpose: To test the hypothesis that females who take Vitamin D supplements (Yes-D) have higher FBF and FVC compared to those who do not take Vitamin D supplements (No-D). Methods: Participants were postmenopausal females, ages 50-70 yrs; exclusion criteria: history of CVD, use of medications determined to alter BP or autonomic function, and body mass index (BMI) of 35kg/m2. Participants completed two study visits. Visit 1: written informed consent and a medical questionnaire to report nutritional supplements taken and age at final menstrual period (age of menopause completion). Visit 2: height and weight were measured to calculate BMI; blood was drawn to measure levels of 25-hydroxyvitamin D3 [25(OH)D3] and total 25-hydroxyvitamin D [25(OH)D]; finger plethysmography was used to measure blood pressure (BP) continuously and two-min of venous occlusion plethysmography was conducted to measure FBF and quantify FVC (calculated as 100 * FBF/mean arterial pressure). Results: Forty-one postmenopausal females (23 Yes-D, 18 No-D) completed all study procedures. Groups were not different in age (Yes-D vs. No-D; mean±SD: 56±9 yrs vs. 58±8 yrs), BMI (25±4 vs. 26±5 kg/m2) or age at menopause completion (45±9 vs. 46±4 yrs, p>0.05 for all). The Yes-D group had higher levels of [25(OH)D3] and total [25(OH)D] compared to the No-D group (47.1±20.0 vs. 36.5±9.4 ng/mL, p=0.033 and 52.3±19.7 vs. 41.3±9.7 ng/mL, p=0.027, respectively). Baseline systolic BP (122±13 vs. 127±13 mmHg, p=0.214), diastolic BP (79±10 vs. 83±10 mmHg, p=0.160) and HR (60±9 vs. 65±12 beats/min, p=0.116) were similar between groups (p>0.05 for all). Forearm blood flow and FVC were higher in the Yes-D group than the No-D group (1.5±0.9 vs. 0.9±0.6 ml/100 ml tissue/min, p=0.01 and 1.3±1.2 vs. 0.8±0.7ml/100 ml tissue/min/mmHg, p=0.004, respectively). These differences persisted after covarying for age, BMI and age of menopause completion. Conclusion: Postmenopausal females who took a Vitamin D supplement exhibited greater levels of [25(OH)D], FBF and FVC compared to females not taking a Vitamin D supplement. These findings suggest that Vitamin D supplementation may positively influence vascular function in postmenopausal females. Funding: F32HL160012 (EJL), T32AG029796 (EJL), NIH 1 K01 AG064038-01A1 (MKR), [NIH CTSA UM1TR004405] This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.