Spinach is full of vitamins and minerals, containing numerous phytonutrients and at least fourteen different flavonoids. Various studies have shown that eating spinach can reduce cancer risk and also leads to the reduction of the cell division of cancer cells. Spinach is high in Vitamin C and A, both of which are natural antioxidants that protect your pet from free radicals. Spinach is high in Vitamin K and an excellent source of folate and magnesium.