grasses occasionally, usually as an emetic. Cats cannot synthesize some essential nutrients required for survival, including the amino acids taurine and arginine, so these nutrients must be sourced from fresh meat in the natural diet. Cats lack the specific physiology to extract nutrients efficiently from plant-based materials, and require a high protein diet, which is why high-energy meats from freshly killed prey are optimal foods. Packaging and labeling In the United States, cat foods labeled as "complete and balanced" must meet standards established by the Association of American Feed Control Officials (AAFCO) either by meeting a nutrient profile or by passing a feeding trial. Cat Food Nutrient Profiles were established in 1992 and updated in 2014 by the AAFCO's Feline Nutrition Expert Subcommittee. The updated profiles replaced the previous recommendations set by the National Research Council (NRC). Certain manufacturers label their products with terms such as premium, ultra premium, natural and holistic. Such terms currently have no legal definitions. However, "While most of the food supplied comes from within the US, the FDA ensures that standards are met within our borders even when components come from countries with less stringent levels of safety or label integrity." Gastrointestinal health The gastrointestinal tract (GIT) is the source of nutrient absorption, making it integral to overall health. Research shows fiber, prebiotics, probiotics, antioxidants and fatty acids are important in maintaining gastrointestinal health. To achieve optimal cellular health (especially in the gut) and to maintain a healthy microbiome, proper nutrition is necessary (nutrition is multifactorial and complex). Cats with gastrointestinal diseases must consume an easily digestible diet with the appropriate nutrients provided by easily digestible ingredients and in the correct ratio which is recommended to be fed in small portions frequently throughout the day, so as not to overwhelm the digestive system. It is also important for fat to be digestible because too much undigested fat that reaches the end of the digestive tract (colon) has the possibility of being fermented and can worsen the symptoms of GIT disease and induce other reactions like diarrhea. It has also been suggested that cats should eat diets tailored to the section of the GIT that is diseased. When certain nutrients like fructooligosaccharides (FOS) are included in the diet, the microbiome and fatty acid content are often changed for the better. An example is less branched-chain fatty acids (BCFAs; which are more difficult and take more time