Compositions and methods are disclosed for treating anxiety or stress in an animal, for reducing elevated levels of 4-EPS in an animal with elevated 4-EPS levels, for preventing elevated levels of 4-EPS in an animal and for promoting growth of beneficial microbes in an animal's microbiome and inhibiting growth of non-beneficial microbes. The methods comprise administering to the animal an effective amount of soy protein and vitamin C. Compositions are disclosed which comprise amounts of soy protein and vitamin C effective for use in the methods.