Age Factor in Food Digestion
The complex process of digestion/absorption can be optimally effective only when the gastrointestinal tract and accessory organs are totally developed and fully functioning. Not only must the muscular tube (alimentary canal) with its mucosal lining and endocrine cells be operating efficiently in conjunction with the nervous system, but the accessory organs (pancreas liver, and gallbladder) with their important digestive secretions also must be physiologically mature.
The feeding of infants is based primarily on the degree of maturation of the gastrointestinal tract and accessory organs. Good examples of the emphasis on gastrointestinal tract maturity are the care given to the fat in infant formula and the time and sequence of the introduction of various foods into the infant’s diet. Only those fats processing, an ease of absorption comparable to that in human milk are used in commercial formula, and the introduction of solid food, beginning with baby cereal usually occurs no earlier than 4 moths old.
The infant pancreas, although structurally mature at term, is unable for several months to produce enzymes sufficient for effective digestion. Pancreatic lipase, alpha-amylase, and the proteolytic enzymes are in too short supply to accommodate digestion of a mixed diet. Digestion of fat is a real concern because there is a deficiency of bile salts from the liver as well as low lipase release from the pancreas.
Solid foods cannot be handled efficiently by the infants’ gastrointestinal tract much before 4 to 6 months, not only because of the deficiency of pancreatic enzymes but also because of poorly coordinated gastric motility. Antral mixing during the very early months of the infant’s life is insufficient for the proper digestion of solid foods.
Particularly attention must be given to the introduction of unmodified cow’s milk and egg white into the infant’s diet. During early infancy intestinal mucosal permeability is greater than normal, and many large molecules, such as low molecular weight proteins, tend to be absorbed intact. Although this absorption has it positive side in that neonates are able to absorb immunoglobulins from their mother’s milk, the increased permeability may allow absorption of proteins such as lactalbumin and egg albumin. Usually by the age of about 2 years the gastrointestinal tract has reached maturity, and digestion/absorption normally becomes efficient, effective process.
Age Factor in Food Digestion
