Researchers study vitamin D metabolism in dogs with diabetes

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Dogs with diabetes exhibited alterations distinct from those seen in human type 1 diabetes, which is linked to hypovitaminosis D, in a study evaluating vitamin D metabolism in these canines. Results of this study, which was the first to use a standardized diet to investigate vitamin D metabolism in dogs with diabetes, were presented with a poster at the 2025 American College of Veterinary Internal Medicine (ACVIM) Forum in Louisville, Kentucky.

Hypovitaminosis D is linked to human insulin resistance as well as an increased risk of type 1 and type 2 diabetes. However, an association between hypovitaminosis D and diabetes in dogs is unclear, although there is a well-established role of hypovitaminosis D in canine autoimmune and inflammatory diseases, according to investigators.

The study’s objective was to assess whether dogs with diabetes exhibit alterations in serum vitamin D status, and to help set a standard diet for these affected canines, according to investigators. “The great finding was that, different from diabetes in humans, the serum vitamin D was not decreased; it was increased,” Camila S. Torelli, MS, the presenting author and a professor at UNIFACCAMP in Sao Paulo, Brazil, said in a dvm360 interview at the ACVIM Forum.

In fact, investigators found that dogs with diabetes had significantly higher mean serum 24,25(OH)₂D₃ concentrations than healthy canines (p = 0.007) in the study. Meanwhile, no significant differences were found in age or median serum calcidiol concentrations between groups (p = 0.09).

The study enrolled 27 dogs with diabetes and free from other diseases, and 19 healthy canines. According to investigators, the dogs with diabetes had a 60-day stabilization period. During this time, they received NPH insulin, and a diet formulated for canine diabetes.

Following the stabilization period, the dogs with diabetes were fed the same diet for 2 months, while healthy dogs in the study were fed the same diet for 60 days. Investigators analyzed serum 25-hydroxyvitamin D₃ (25(OH)D₃, calcidiol) and 24,25-dihydroxyvitamin D₃ (24,25(OH)₂D₃), and used Wilcoxon or t-tests to compare dogs with diabetes to healthy canines.

Investigators noted the findings align with human juvenile insulin-dependent diabetes, for which increased calcidiol and serum 24,25(OH)₂D₃ concentrations have also been observed. In the poster presentation, they wrote that these elevated serum concentrations found may be caused by mitochondrial stimulation of 24-hydroxylase by diabetes metabolites, a scenario that has been reported in insulin-dependent rats.

Torelli said these study results can lead to more studies on diabetes and metabolism as well as other perspectives for treatment and diagnosis. “Diabetes is definitely something that people are interested in learning more about. It's revealing to be something of big complexity, with diagnosis, treatment, with prognosis,” she concluded.

Reference

Pereira EF, Torelli C, Torres de Almeida Villar S, et al. Serum vitamin D metabolites in diabetic dogs. Presented at: American College of Veterinary Internal Medicine (ACVIM) Forum; June 18-21, 2025. Louisville, KY.