title: Vitamin D Supplementation and Hemoglobin Levels in Hypertensive Patients: A Randomized Controlled Trial.
abstract: Epidemiological evidence suggests that circulating 25-hydroxyvitamin D (25OHD) levels are inversely associated with hemoglobin (Hb) levels and anemia risk. We evaluated whether vitamin D supplementation improves Hb levels and reduces anemia risk in hypertensive patients. Two hundred patients with 25OHD levels <75 nmol/L who attended the Styrian Vitamin D Hypertension Trial were included, of whom 188 completed the trial. Patients randomly received 2800 IU vitamin D3 daily or a matching placebo for eight weeks. Initially, the prevalence of anemic status (Hb levels <12.5 g/dL) and deficient 25OHD levels (<30 nmol/L) was 6.5% and 7.5%, respectively. All anemic patients had 25OHD levels >50 nmol/L. The mean (95% confidence interval) vitamin D effect on Hb levels was 0.04 (-0.14 to 0.22) g/dL (P = 0.661). Moreover, vitamin D treatment did not influence anemic status significantly (P > 0.999). Likewise, vitamin D had no significant effect on Hb levels in the subgroups of anemic patients or in patients with initial 25OHD levels <30 nmol/L. In conclusion, a daily vitamin D supplement of 2800 IU for eight weeks did not improve Hb levels or anemic status in hypertensive patients. Future trials should focus on anemic patients with deficient 25OHD levels (e.g., <30 nmol/L). This trial is registered with clinicaltrials.gov [NCT02136771].
authors.affiliation: Clinic for Thoracic and Cardiovascular Surgery, Heart and Diabetes Center NRW, Ruhr University Bochum, Georgstraße 11, 32545 Bad Oeynhausen, Germany.
authors.forename: Jana B
authors.initials: JB
authors.lastname: Ernst
authors.affiliation: Department of Cardiology, Medical University of Graz, Auenbruggerplatz 15, 8036 Graz, Austria; Specialist Clinic for Rehabilitation Bad Aussee, Braungasse 354, 8990 Bad Aussee, Austria; Department of Cardiology, Charité University, Campus Virchow, Augustenburger Platz 1, 13353 Berlin, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Tomaschitz
authors.affiliation: Department of Internal Medicine, Division of Endocrinology and Metabolism, Medical University of Graz, Auenbruggerplatz 15, 8036 Graz, Austria; Swiss Cardiovascular Center Bern, Department of Cardiology, Bern University Hospital, 3007 Bern, Switzerland.
authors.forename: Martin R
authors.initials: MR
authors.lastname: Grübler
authors.affiliation: Department of Internal Medicine, Division of Endocrinology and Metabolism, Medical University of Graz, Auenbruggerplatz 15, 8036 Graz, Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Gaksch
authors.affiliation: Department of Internal Medicine, Division of Endocrinology and Metabolism, Medical University of Graz, Auenbruggerplatz 15, 8036 Graz, Austria.
authors.forename: Katharina
authors.initials: K
authors.lastname: Kienreich
authors.affiliation: Department of Cardiology, Medical University of Graz, Auenbruggerplatz 15, 8036 Graz, Austria.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Verheyen
authors.affiliation: Medical Clinic V (Nephrology, Hypertensiology, Endocrinology, Diabetology, Rheumatology) Mannheim Medical Faculty, University of Heidelberg, Theodor-Kutzer-Ufer 1-3, 68167 Mannheim, Germany; Clinical Institute of Medical and Chemical Laboratory Diagnostics, Medical University of Graz, Auenbruggerplatz 15, 8036 Graz, Austria; Synlab Academy, Synlab Laboratory Services GmbH, P5, 7, 68161 Mannheim, Germany.
authors.forename: Winfried
authors.initials: W
authors.lastname: März
authors.affiliation: Department of Internal Medicine, Division of Endocrinology and Metabolism, Medical University of Graz, Auenbruggerplatz 15, 8036 Graz, Austria; Department of Epidemiology and Biostatistics, EMGO Institute for Health and Care Research, VU University Medical Center, Van der Boechorststraat 7, 1081 BT Amsterdam, Netherlands.
authors.forename: Stefan
authors.initials: S
authors.lastname: Pilz
authors.affiliation: Clinic for Thoracic and Cardiovascular Surgery, Heart and Diabetes Center NRW, Ruhr University Bochum, Georgstraße 11, 32545 Bad Oeynhausen, Germany.
authors.forename: Armin
authors.initials: A
authors.lastname: Zittermann