Can dogs eat a fully vegetarian diet? Experts are still on the fence as to whether they can or not. Cailin Heinz, a board-certified veterinary nutritionist at the Cummings School of Veterinary Medicine at Tufts University, states, ?From a biological perspective, dogs lack most of the metabolic adaption to a strict diet of animal flesh? and [they] can easily utilize vitamin A and D from plant sources, just as people do. We also have evidence that they also evolved from wolves by eating more plant material.? That being said, dogs can go on a full vegetarian or vegan diet if it?s done with care.