Age Factor in Food Digestion

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

How Gastrointestinal Tract Function?

How Gastrointestinal Tract Function?
An examination of the various mechanisms in the gastrointestinal tract that allow to be ingested, digested, absorbed, and then its residue to be excreted reveals the complexity of the digestion/absorption process. Normal digestion and absorption of nutrients is dependent not only on a healthy alimentary canal but also on an exquisite integration of the digestive system with the nervous system, endocrine system, and circulatory system. An excellent example of this integration of systems is the finely controlled emptying of chyme from the stomach into the small intestine.

The many factors influencing digestion and absorption, including the dispersion and mixing of ingested food, the quantity and composition of gastrointestinal secretions, status of the enterocytes, expanse of intestinal absorptive area and the transit time of intestinal contents must be coordinated so that nourishment of the body can occur while homeostasis of body fluids is maintained. Much of the coordination required is provided by regulatory peptides, some of which are provided by the nervous system as well as by the endocrine cells of the gastrointestinal tract.
How Gastrointestinal Tract Function?

The Importance of Adequate Fiber Intake

The Importance of Adequate Fiber Intake
The importance of adequate intake of fiber to the improvement of health is demonstrated by some of the physiologic effects exerted by its various components. Particularly noteworthy are the hypoglycemic and hypolipidemic effect of soluble fiber. Slowing the absorption rate of carbohydrate can be very helpful to the diabetic in regulating blood glucose levels and lowering serum cholesterol levels presently appears to have significant benefit in the prevention of atherosclerosis.

Wheat 

Adequate fiber intake has been implicated in control of various gastrointestinal disorders, including diverticular disease, gallstones, irritable-bowel syndrome, inflammatory bowel disease, and constipation. It was suggested that fiber, especially wheat bran, is effective in the treatment of constipation; but evidence for the effectiveness of fiber in control of the other diseases seems equivocal. Nevertheless, populations with high fiber intakes have a lower incidence of these gastrointestinal disorders.

A generous fiber intake appears to be beneficial to some individual in their efforts at weight control. The bulk provided by fiber may have some satiety value, so that high fiber foods possibly reduce the hunger pangs associated with caloric restriction while simultaneously somewhat reducing nutrient utilization. The anti-toxic effect of fiber is a physiologic role often overlooked. Results of studies on experimental animals, particularly growing rats, have shows the protective effects of selected fiber supplements against a variety of toxic agents.
The Importance of Adequate Fiber Intake

Physiologic Roles of Dietary Fiber

Physiologic Roles of Dietary Fiber
Certain physical properties of fiber such as particle size influence its effect in the gastrointestinal tract. Important characteristics of dietary fiber in relation to its physiologic role include hydration, capacity, adsorptive attraction for organic molecules, cation exchange capacity and fermentability. Fiber exerts its effect throughout the gastrointestinal tract beginning in the mouth. Fiber components that cannot be solubilized (lignin, cellulose and most of the hemicellulose) require increased chewing, thereby stimulating, saliva secretion and serving somewhat as a tooth cleanser.

Often dietary fiber is classified as soluble or insoluble in order to more easily explain its physiological functions. This classification is imprecise, however, because determination of soluble fiber is very difficult and the amount resulting from fiber analysis is influenced by the method used.

The food providing dietary fiber can have a decisive influence in the gastrointestinal tract responses elicited because sources of fiber vary in the relative amount of the different fiber components. For example wheat bran, is primarily hemicellulose, while most fruits, and vegetables contain almost equal quantities of cellulose and pectin. Dietary fiber composition of plant depends on the plant species, the part of the plant consumed (leaf, root, stem) and its maturity. For example lignin is found relatively small amounts in edible plants; its content is highest in fruits with edible seeds, such as strawberries, and in mature root vegetables, such as carrots.
Physiologic Roles of Dietary Fiber