title: Short-term vitamin A supplementation does not affect bone turnover in men.
abstract: Limited data in humans and animals indicate that excess vitamin A stimulates bone resorption and inhibits bone formation, effects that over time might lead to bone loss and fracture. Thus, it is possible that vitamin A supplementation is a currently unrecognized risk factor for the development of osteoporosis. To further evaluate this possibility, a prospective, randomized, single-blind study of vitamin A supplementation was conducted in 80 healthy men age 18-58 y. One half received 7576 microg (25,000 IU) of retinol palmitate daily with their evening meal; the others took a placebo. Blood was collected from fasting subjects and serum prepared at baseline and after 2, 4 and 6 wk of supplementation. Serum bone specific alkaline phosphatase (BSAP) and N-Telopeptide of type 1 collagen (NTx) were measured at all time points. Serum osteocalcin (Oc) was measured at baseline and after 6 wk of supplementation. BSAP, NTx and Oc did not differ between the supplemented and placebo-treated groups over the course of the study. In conclusion, short-term vitamin A supplementation at this dosage in healthy men does not alter serum markers of skeletal turnover. Thus, it is unlikely that short-term administration of vitamin A would contribute to the development of osteoporosis. Whether long-term vitamin A supplementation might have adverse skeletal effects remains to be determined.
authors.affiliation: Institute on Aging, University of Wisconsin-Madison, Madison, WI, USA. tnkawahara@facstaff.wisc.edu
authors.forename: Tisha N
authors.initials: TN
authors.lastname: Kawahara
authors.forename: Diane C
authors.initials: DC
authors.lastname: Krueger
authors.forename: Jean A
authors.initials: JA
authors.lastname: Engelke
authors.forename: Judy M
authors.initials: JM
authors.lastname: Harke
authors.forename: Neil C
authors.initials: NC
authors.lastname: Binkley
mesh_terms: D000293:Adolescent; D000328:Adult; D000469:Alkaline Phosphatase / Q000097:blood; D001862:Bone Resorption / Q000209:etiology; D001842:Bone and Bones / Q000187:drug effects / Q000378:metabolism*; D003094:Collagen / Q000097:blood; D024042:Collagen Type I; D019587:Dietary Supplements; D006801:Humans; D006986:Hypervitaminosis A / Q000150:complications* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D015675:Osteocalcin / Q000097:blood; D010024:Osteoporosis / Q000209:etiology*; D010455:Peptides / Q000097:blood; D010919:Placebos; D011446:Prospective Studies; D012307:Risk Factors; D016037:Single-Blind Method; D014801:Vitamin A / Q000008:administration & dosage* / Q000009:adverse effects
chemical_list: D024042:Collagen Type I; D010455:Peptides; D010919:Placebos; C052929:collagen type I trimeric cross-linked peptide; D015675:Osteocalcin; D014801:Vitamin A; D003094:Collagen; D000469:Alkaline Phosphatase