Effects of Vitamin D on Cardiovascular Health in Black Women

The goal of this clinical trial is to understand the effects of oral vitamin D3 supplementation on various cardiovascular risk factors in generally healthy, young adult black women who are vitamin D deficient or insufficient at baseline.The main questions it aims to answer are:Does 8 weeks of vitamin D3 supplementation (5,000 IU per day) improve 24 hour blood pressure metrics in generally healthy, young adult black women who are vitamin D deficient or insufficient at baseline?Does 8 weeks of vitamin D3 supplementation (5,000 IU per day) improve objectively estimated sleep duration and regularity in generally healthy, young adult black women who are vitamin D deficient or insufficient at baseline?Does 8 weeks of vitamin D3 supplementation (5,000 IU per day) improve various measures of blood vessel structure and function in generally healthy, young adult black women who are vitamin D deficient or insufficient at baseline?All participants will undergo baseline testing, which includes 2 continuous weeks of objective sleep monitoring using a sleep watch, one 24-hour period of ambulatory blood pressure monitoring, and one blood vessel function testing visit. Following baseline testing, participants will be randomized to take either 5,000 IU of vitamin D3 or a placebo pill daily for 8 continuous weeks. Participants will undergo 2-weeks of sleep monitoring again during weeks 3-4 of the supplementation period and during weeks 7-8 of the supplementation period. Additionally, 24-hour blood pressure monitoring will be performed during week 4 and week 8, and blood vessel function testing will take place at the end of week 4 and again at the end of week 8.Researchers will compare the vitamin D3 and placebo groups to see if there is any effect of vitamin D3 supplementation on 24-hour blood pressure, sleep duration and regularity, and blood vessel structure and function following 4 and 8 weeks of supplementation.

Inclusion Criteria:FemaleSelf-identified race is black18-40 years oldSerum 25-hydroxyvitamin D concentration between 8-29.9 ng/mlExclusion Criteria:Currently taking vitamin D supplements or multivitamins that contain vitamin DUnwilling or unable to give consentUnwilling or unable to undergo a venous blood drawDiagnosed with any chronic diseases or conditions including cardiometabolic diseases, cardiorespiratory diseases, chronic mental or psychological illness, musculoskeletal diseases/conditions, autoimmune diseases, cancer, gastrointestinal/malabsorption disorders, hyper-/hypocalcemia, hyper-/hypoparathyroidism, hyper-/hypothyroidismTaking medication that may influence blood pressure or blood vessel functionDiagnosed with a sleep disorder (e.g., insomnia, restless leg syndrome, sleep apnea), or are at high risk for a sleep disorder according to the ISI (score >14) or STOP-bang (score ≥3) questionnairesCurrently taking medications or supplements that affect sleep (e.g., Ambien, sedatives, melatonin, etc.)Currently working night-shift workResting blood pressure >130 or >80 mmHgBMI >30 kg/m2Currently pregnant, breast feeding, peri-menopausal, or post-menopausalCurrently use tobacco (≥1 cigarette in the last month)Had COVID-19 in the past 60 daysReceived the COVID-19 vaccine or booster within in the past 14 days