Canine and feline nutritional requirements reflect evolutionary experience extending hundreds of thousands of years into the past. Until recently, dogs and cats always ate a diet based upon real, raw foods. Scientists are learning more every day about the values of phytochemicals, enzymes, antioxidants, bioflavonoids and essential fatty acids, especially the Omega-3s. Recent research, for example, is focusing on the cancer fighting properties of phytochemicals. There are tens of thousands of phytochemicals, which occur naturally in vegetables and fruits.