While earning a Ph.D. in nutritional sciences, I took multiple graduate-level classes that covered the biological functionality of vitamin D. It is a finicky vitamin that can cause both deficiencies and toxicities. While some animals can generate sufficient quantities with exposure to sunlight, most of our pets require dietary supplementation for normal metabolism and bone development. While the collective knowledge of vitamin D requirements in various animal species has been refined over time, nutrition education often overlooks an important aspect of meeting these requirements: nutrient delivery.
As a fat-soluble vitamin, vitamin D has the potential to cause both a nutrient deficiency and nutrient toxicity. The classic essential nutrient trapezoid (see Figure 1) best illustrates this concept. When vitamin D levels fall below an animal’s requirement, the animal is considered deficient. In pets, these symptoms can include bone abnormalities, poor growth and heart disease. Increasing levels of the essential nutrient will linearly improve these symptoms up to the animal’s requirement.
