Based on laboratory analyses of both vegan and meat-based pet foods, some studies have suggested pet food samples of either type to be nutritionally sound, while others have demonstrated nutritional flaws. However, a more systematic evaluation of the nutritional soundness of vegan and meat-based pet foods has been lacking. Consequently, this study sought to more comprehensively review relevant published studies to date. Overall, 54 suitable studies were located and assessed. In total, 81.5% of the studies (n = 44) found nutritional inadequacies in the pet foods they examined. These nutritional inadequacies spanned multiple pet food types—both vegan and meat-based, and both dog and cat food. The nutritional inadequacies concerned multiple nutrients. There was no increased overall tendency for vegan diets to suffer from these problems.
It is also important to remember that the most important thing for pet welfare is not diet, but health outcomes. These have been studied in a sizeable body of studies, and are normally positive when modern, commercial vegan diets are fed. Pets, like people, have bodily reserves that allow them to compensate for temporary nutritional deficiencies. This may be one reason why health outcomes are normally good.