Digestion is the process of extracting nutrients and other essential substances from the food and drink we consume. This is done by breaking down what is consumed into forms that can be used by the body. Meat, as explained by the National Digestive Diseases Information Clearinghouse, has large protein molecules that must be broken down into much smaller amino acid molecules before the body is able to put it to work building and repairing its tissues. The body can digest a variety of meats. However, the rate of digestion can be affected by a variety of factors, including health and method of meat preparation.
Digestion is a chemical process, as demonstrated by numerous formal experiments. According to an article from the Departments of Biochemistry and Medicine, University of Toronto, written by researcher Ernest J. Maltby in 1933, gastric diseases that affect the balance of digestive enzymes and chemicals present in the body can slow the rate of digestion of beef. Maltby's work also revealed that the ageing process can slow beef digestion, due to a measurable reduction in those enzymes as people age. Researchers at the French National Institute for Agricultural Research studying the bioavailability of beef proteins in 2006 found that the cut of beef and the amount of connective tissues present affect digestion, along with the means of preparation. Beef with a greater proportion of connective tissues digested better when minced or cooked for a longer period of time. Their experiments found that "grilled sirloin was that which exhibited the highest rate of digestion."
Pork does take longer to digest than beef, according to research published by the Laboratory of Physiological Chemistry at Jefferson Medical College in Philadelphia in 1919. However, like beef, cooking time and preparation style, such as mincing or grinding, can shorten digestion time. Researchers found that, for example, pork roast spends just over five hours in the stomach, while broiled pork sausage is there for an average of three hours and 15 minutes. Boiled pig's feet spent a mere 60 minutes in the stomach. Fortunately, according to research done by the University of Illinois Department of Animal Sciences and Division of Nutritional Sciences, "protein quality and metabolisable energy yield of pork" are not adversely affected by the length of cooking time, so cooking pork longer to make it more digestible is not going to reduce its nutritional value.
The rate of digestion for poultry is also affected by cooking times and the means of preparation. Like most meat, poultry is an important source of protein and iron. As the protein molecules in meat are very large, they must be broken down into smaller amino acid molecules for the body to be able to use it. A 1929 Time Magazine article noted that "a quarter-pound of meat stimulates almost twice as much gastric juices as does a quarter-pound of bread or other carbohydrates," giving meat an important role in helping to digest the other elements of a meal.
Fish is often touted for ease of digestion and the bioavailability of its nutrients, and with good reason. According to research done by the Department of Animal Sciences at the University of Illinois and the Department of Seafood Science and Technology at the University of Alaska, fish is a very digestible meat, one that is readily used by the body.