Blueberries have been proven to help control dogs' sugar levels and cardiovascular health. The fiber, magnesium, and vitamin K all improve heart function as well as lower stroke risk. They are extra-helpful for animals who engage in a great deal of exercise, as they help with cell repair. Studies with sled dogs have shown the antioxidant properties help them fight free radicals as well as resist normal wear and tear. The anti-cancer properties are also undisputed and part of a healthy diet for active dogs. Blueberries have been shown to help older dogs improve cognitive function, evidenced by heightened ability to perform tasks and learn new commands.