Maitake mushroom (Grifola frondosa) is used in pet supplements primarily for its potential immune-modulating and anti-cancer properties. The scientific basis for its use in pets is limited but growing, with most evidence extrapolated from laboratory and rodent studies, as well as small-scale clinical trials in dogs. Maitake contains polysaccharides, particularly beta-glucans, which are believed to stimulate the immune system by activating macrophages, natural killer cells, and T-cells. In veterinary settings, maitake is often included in supplements aimed at supporting dogs or cats undergoing cancer treatment or those with compromised immune systems.

Several preclinical studies have shown that maitake extracts can inhibit tumor growth and enhance immune activity in rodents. A few pilot studies in dogs, such as those with hemangiosarcoma, have suggested possible survival benefits or improved quality of life when maitake extracts are used as adjunct therapy, but these studies are small and not definitive. Overall, while there is scientific rationale and some early evidence supporting the immune-enhancing and anti-cancer effects of maitake in pets, robust clinical trials in companion animals are lacking. The evidence is therefore rated as 2 out of 5—suggestive but not conclusive. Veterinarians may recommend maitake as part of an integrative approach, but more research is needed to confirm efficacy and safety in pets.