A vitamin D insufficiency is associated with a range of disease states.
In recent years, researchers have uncovered new findings about vitamin D in dogs and cats. Diseases such as congestive heart failure, neoplasia, renal disease, infectious illnesses, IBD, and feline oral resorptive lesions (FORL) are all associated with low stores of vitamin D in these animals.
Vitamin D primarily regulates the absorption of calcium and phosphorus from the bowel, and in concert with calcitonin and PTH, regulates calcium homeostasis. Vitamin D also has an anti-inflammatory effect in the tissues where it is active.
Chronic inflammation underlies many chronic conditions, including neoplasia and immune-mediated disease. It is apparent that serum vitamin D levels high enough to prevent the development of rickets are still insufficient for maintaining cellular health and dampening inflammatory processes.
Normal ranges of serum vitamin D3
In a landmark study involving 282 German shepherds and golden retrievers, Selting et al (2014) established optimal ranges for vitamin D in dogs. Following protocols used in human studies, 25(OH)D3 was measured along with four other biomarkers: canine C-reactive protein (cCRP), intact parathyroid hormone (iPTH), calcium and phosphorus. The study examined the inverse relationship between 25(OH)D3 and iPTH, as well as the anti-inflammatory effects of vitamin D by measuring cCRP.
This study established that vitamin D sufficiency is obtained when blood levels reach 100 to 120 ng/mL and helped further define deficiency, insufficiency and sufficiency.
Insufficient vitamin D may be a risk factor for neoplasia
• Wakshlag et al (2011) found that Labrador retrievers with cutaneous mast cell tumors had significantly lower serum concentrations of 25(OH)D than unaffected controls (42 ng/ mL versus 48 ng/mL).
• Husbands (2013) reported that median serum 25(OH)D concentrations were significantly lower in dogs with cancer versus dogs without. He evaluated 335 dogs with cancer and found a median 25(OH)D concentration of 62.6 ng/mL as compared to 67.4 ng/mL in the control group. Additionally, it was reported that cancer types associated with significantly lower 25(OH)D levels were: carcinoma, histiocytic sarcoma, hemangiosarcoma, lymphoma and sarcoma.
• Selting et al (2014) measured the serum concentrations of 25(OH)D in 62 dogs presenting with hemoabdomen due to neoplasia, and compared them to 282 healthy dogs without neoplasia. The relative risk of splenic neoplasia was found to be inversely proportionate to 25(OH)D concentrations.
Based on the evidence that vitamin D insufficiency creates a greater risk for chronic disease, vitamin D testing and supplementation should become part of annual wellness programs and testing protocols. By sampling patients for vitamin D status at the same time each year, when heartworm and other preventative tests such as vaccine titers are performed, clinicians can identify dogs and cats at higher risk, and through oral supplementation and retesting, establish long-term vitamin D sufficiency, and with it a reduced risk of developing chronic disease.