Dietary components play a crucial role in the health of companion animals, especially those exposed to elevated levels of toxins and free radicals. Investigation into animals' hepatic antioxidant and metabolite conjugation systems, and the metabolic processes that influence them, provides some understanding regarding the relationship of diet to disease prevention and treatment. A review of current literature and research publications suggests nutritional supplementation can be an effective treatment for animals suffering from increased oxidative stress and toxicity. The results of recent in vivo assessments, clinical trials, and observational studies show oral supplementation with vitamin E, selenium, glutathione, and taurine to be beneficial for both maintaining natural antioxidant systems and protecting against a number of degenerative diseases associated with free radical damage and toxin exposure. In many instances, it has been observed that the introduction of specific nutrients positively influences the health status, symptomatic presentation, and life span of animals whose natural detoxification systems are compromised.