Papaya extracts and papaya-associated phytochemicals possess anti-inflammatory and immunomodulatory properties. Papaya contains a wide range of bioactive secondary metabolites (eg alkaloids, phenolics, flavonoids, carotenoids, tannins, saponins) and proteolytic enzymes (papain and chymopapain).
Both marigold and papaya are also rich in lutein, a type carotenoid. The importance of carotenoids in promoting health in people and dogs is well documented.
However, a study on 56 young beagles receiving a dietary lutein supplement, showed a significantly enhanced cell-mediated and humoral immune response in dogs. The study also showed that dietary lutein may enhance the antibody response of dogs given routine vaccinations.