In the first of the studies, vets are assessing dogs that have had surgery to repair damage to their knee ligaments.
Edinburgh University's Royal (Dick) School of Veterinary Studies aims to improve health outcomes for pets receiving veterinary care.
The team will explore whether dogs can also produce vitamin D in their skin after exposure to the sun.
Previous studies have shown that animals with lower levels of vitamin D in their blood often show signs of increased inflammation.
The team will examine whether inflammation linked to reduced intake can hamper dogs' recovery from surgery.
Blood samples will be taken before and after surgery to allow the team to measure their levels and any symptoms of inflammation.
They will then monitor the dogs to see whether having higher levels of vitamin D before surgery have a positive effect on their recovery.
If a link is found, researchers will test if supplements can help to lower inflammation and improve the chances of better recovery from surgery.
In a separate study, vets will investigate how dogs acquire vitamin D in the first place, taking blood samples to examine whether levels fluctuate with the changing seasons.
The findings will help to determine whether dogs are getting enough vitamin D in their diet throughout the year.
Dr Richard Mellanby, Edinburgh University's head of veterinary clinical research and companion animal sciences, said: "Vitamin D plays a vital role in bone health and there is growing evidence that it has other health benefits for people and animals.
"Our research aims to understand whether dogs' vitamin D levels fluctuate throughout the year, which is important for making sure we're feeding our pets the right diet.
"We're also interested in how vitamin D affects recovery after surgery and whether having less vitamin D is a cause or consequence of inflammation.
"Untangling this complex relationship will help us to devise new approaches to improve the welfare of animals after surgery."
Pet dogs are being used in a research project to look at the effects of vitamin D on their health.