Are commonly recommended dosages for vitamin D supplementation too low? Vitamin D status and effects of supplementation on serum 25-hydroxyvitamin D levels--an observational study during clinical practice conditions.
Vitamin D deficiency is associated with increased fracture risk. The observational study aimed to investigate vitamin D status and supplementation in ambulatory patients. Only 20% of patients had optimal serum 25-hydroxyvitamin D [25(OH)D] levels. Commonly recommended dosages were insufficient to achieve clinically relevant increase of 25(OH)D levels. Higher dosages were safe and effective under clinical practice conditions.


BACKGROUND
Vitamin D deficiency is associated with adverse health outcome. The study aimed to investigate vitamin D status and supplementation in ambulatory patients.


METHODS
Nine hundred seventy-five women and 188 men were evaluated for bone status from January 2008 to August 2008 within an observational study; 104 patients (n = 70 osteoporosis) received follow-up after 3 months. Dosage of vitamin D supplementation was documented and serum 25(OH)D and parathyroid hormone (PTH) determined.


RESULTS
In all patients (age, 60.4 ± 14.1 years), distribution of 25(OH)D was 56.3 ± 22.3 nmol/L (normal range, 52-182 nmol/L) and PTH 53.8 ± 67.5 ng/L (normal range, 11-43 ng/L). The proportion of patients with 25(OH)D < 25, 25 to <50, 50 to <75, ≥75 nmol/L was 7.5%, 33.3%, 38.9% and 20.2% in the total group and 20.1%, 38.5%, 30.8%, 10.6% at baseline in the follow-up group, respectively. After 3 months, 3.9% had still 25(OH)D < 25 nmol/L; only 12.5% achieved 25(OH)D ≥ 75 nmol/L. In osteoporosis patients, 25(OH)D increased more in those taking ≥1,500 (median, 3,000) IU vitamin D per day (33.1 ± 14.7 nmol/L) compared with ≤1,000 (median, 800) IU/day (10.6 ± 20.0 nmol/L) (p < 0.0008). PTH decreased more in patients taking ≥1,500 IU/day (-13.2 ± 15.2 ng/L) compared with ≤1,000 IU/day (-7.6 ± 19.2 ng/L; p = 0.29). 25(OH)D was negatively correlated to PTH (r = -0.49, p < 0.0001). An increase of 25(OH)D ≥ 75 nmol/L resulted in normalised PTH.


CONCLUSIONS
Supplementation with higher vitamin D dosages (2,000-3,000 IU/day) is required to achieve a relevant increase of 25(OH)D and normalisation of PTH.
Leidig-Bruckner
G
G
Gemeinschaftspraxis für Endokrinologie, Nuklearmedizin und Humangenetik, Brückenstr. 21, 69120, Heidelberg, Germany. thomas.bruckner@t-online.de
Roth
H J
HJ
Bruckner
T
T
Lorenz
A
A
Raue
F
F
Frank-Raue
K
K
D000368:Aged; D015519:Bone Density; D001842:Bone and Bones / Q000378:metabolism; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D005260:Female; D005272:Femur Neck / Q000503:physiopathology; D005500:Follow-Up Studies; D006801:Humans; D049950:Hyperparathyroidism, Primary / Q000097:blood / Q000150:complications; D008159:Lumbar Vertebrae / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D010024:Osteoporosis / Q000097:blood / Q000209:etiology; D010281:Parathyroid Hormone / Q000097:blood; D014807:Vitamin D / Q000008:administration & dosage* / Q000031:analogs & derivatives / Q000097:blood / Q000627:therapeutic use; D014808:Vitamin D Deficiency / Q000097:blood / Q000150:complications / Q000188:drug therapy*
D010281:Parathyroid Hormone; D014807:Vitamin D; C104450:25-hydroxyvitamin D