title: The effect of diet on serum 25-hydroxyvitamin D concentrations in dogs.
abstract: BACKGROUND
  Vitamin D (vitD) deficiency is linked to many disease states including rickets and cancer, and vitD supplementation to improve response to cancer therapy has been explored. Supplementation may be most appropriate for dogs with suboptimal vitD concentrations. In dogs, the primary source of vitD is diet (predominantly via commercial dog food). Our goal was to determine how food source and supplements affect 25(OH)D concentrations, the storage form of vitD. Serum was collected from clinically healthy dogs, and pet owners were surveyed about food source and supplements. Serum 25(OH)D concentration was measured using a quantitative chemiluminescent assay (LIASON, DiaSorin, Stillwater, MN).
  
  
  RESULTS
  Dogs (n = 320) were tested for serum 25(OH)D concentrations (range 9.5-249.2 ng/mL). Dogs were fed commercial diets from forty different manufactures (n = 292); additionally some dogs were fed homemade diets (n = 18) or a combination of commercial and homemade diets (n = 10). Median serum 25(OH)D concentrations in dogs fed commercial foods ranged from 47.4 to 100.1 ng/mL with an overall median of 67.9 ng/ml (CV 29%). Analysis for differences among manufacturers was significant (P = 0.0006). Serum 25(OH)D concentrations amongst dogs fed homemade diets had the largest range (9.5-129 ng/mL) and the lowest value (9.5 ng/mL). Dogs receiving salmon oil as a supplement (n = 22) had significantly higher serum 25(OH)D (on average a 19.6 ng/mL increase) than those not receiving a supplement (P = 0.007).
  
  
  CONCLUSIONS
  Serum 25(OH)D concentrations in dogs vary widely which likely reflects varying dietary vitD content. Notable differences exist among manufacturers and brands and may reflect differences in proprietary formulations. Given the variability of measured serum 25(OH)D concentrations in dogs and the importance vitD appears to have on health status, dietary vitD content should be optimized.
authors.affiliation: Cummings School of Veterinary Medicine, Tufts University, 200 Westboro Road, North Grafton, MA, 01536, USA. Claire.Sharp@tufts.edu.
authors.forename: Claire R
authors.initials: CR
authors.lastname: Sharp
authors.affiliation: Veterinary Medical Teaching Hospital, University of Missouri, Columbia, MO, 65211, USA. seltkingk@missouri.edu.
authors.forename: Kim A
authors.initials: KA
authors.lastname: Selting
authors.affiliation: Veterinary Diagnostics Institute, Simi Valley, CA, 93063, USA. ringoldr@vdilab.com.
authors.forename: Randy
authors.initials: R
authors.lastname: Ringold
mesh_terms: D000818:Animals; D001947:Breeding; D004032:Diet; D019587:Dietary Supplements; D004285:Dogs / Q000097:blood*; D005260:Female; D008297:Male; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D