The gastrointestinal system extracts essential vitamins and
minerals from diverse plant and animal foods and breaks down the
carbohydrate, protein, and fat molecules to smaller subunits that can
be absorbed. It accomplishes these tasks by means of the various
digestive organs of the body and the enzymes. (See Digestive System.)
The diet must provide, sufficient nutrients and energy to synthesize
the rapidly renewing cells that line the gastrointestinal tract, the
enzymes that digest and transport nutrients across the intestinal
walls, and other hormones that control these processes. Digestive
function can be seriously disrupted by inadequate nutrition.
Diseases of the gastrointestinal tract will unavoidably have
profound effects on nutritional and metabolic processes. Loss of body
weight is often an indication of gastrointestinal disease and a diet
history may reveal obvious nutritional deficiencies associated with the
underlying disease, eating problems, and psychological problems.
Dietary fat, fiber, and alcohol are significant factors associated
with gastrointestinal diseases. Higher intakes of dietary fiber can
prevent or relieve symptoms of constipation and chronic diverticular
disease. Individuals with celiac disease should obtain information on
foods free of wheat gluten. Those with inflammatory bowel disease,
heart-burn, and ulcers should follow diets appropriate to their
conditions.
Diseases of the Mouth
Dental caries result from demineralization of the enamel surface of
the tooth by acids produced from sugars. Initially mineral disappears
from the sub-surface of the tooth and if this process is not addressed
a cavity will develop in which more bacterial growth can occur causing
further dissolution of enamel. Eventually the tooth may be lost.
The presence in the mouth of fermentable sugars is essential for the
development of dental caries. Within minutes of consumption sugars
cause the pH in dental plaque to fall below the critical pH for enamel
dissolution. This fall in pH will occur irrespective of the amount of
sugar consumed or whether it comes from fruit or chocolate. The normal
oral pH of 7.0 will only be restored about 30 minutes after the sugar
has finally been swallowed. Normally the pH will return sooner if the
item is consumed quickly rather than if eaten slowly over a long period
of time.
Acidic foods, such as citrus fruits and cola drinks, lower the mouth
pH and hence produce cariogenic conditions. Finishing a meal with an
alkaline food, such as cheese, milk, or peanuts can help to raise the
pH of the mouth.
Fluoride can increase enamel resistance by the formation of
fluorhydroxyapatite crystals in the tooth which are more resistant to
acid erosion. The maximum benefit from fluoride is obtained if it is
available during tooth formation. Once the tooth has emerged, further
protection can be obtained from topical or dietary fluoride.
Deficiency of certain vitamins may produce inflammation of the gums
and the teeth may become loose from the lack of cement which normally
holds them to the jaw. A lack of vitamin C causes scurvy, a weakening
of periodontal fibers and the teeth may become loose and fall out. The
gums become tender and bleed easily. Treatment is by vitamin therapy
and sources of vitamin C should be included in the diet regularly.
Deficiency of vitamin D causes defective calcification of the
dentine of the teeth and may increase susceptibility to dental caries.
Eruption of the teeth may be delayed in children with rickets. Vitamin
D therapy should be given and good sources of vitamin D taken in the
diet, together with exposure to sunlight where possible.
Disorders of the esophagus
The diaphragm has several openings through which the abdominal
viscera can enter the thorax. The opening for the esophagus, the
hiatus, is loosely attached to the esophagus. In middle age this
attachment weakens and in overweight people additional abdominal weight
puts extra strain on the hiatus which herniates. A low fiber diet which
results in constipation causes straining when the bowels are opened and
weakening of the hiatus. The major symptoms of hiatus hernia are those
of reflux and esophagitis and the sensation of food 'sticking'.
The refluxed contents of the stomach may contain partly digested
foods, acids and enzymes. It is possibly this combination which causes
mucosal damage and esophagitis. Symptoms develop if reflux becomes
frequent and the mucosa of the esophagus becomes sensitive to the
acidic reflux. Fatty foods, chocolate, coffee, alcohol, spicy foods and
citrus juices lower sphincter pressure and may induce reflux.
Cystic fibrosis
Cystic fibrosis (CF) is a generalized hereditary condition
characterized by chronic pulmonary disease, reduced secretion of water
and bicarbonate, pancreatic enzyme deficiency and abnormally high
concentrations of electrolytes in the sweat.
Progressive malnutrition and poor growth are common features of CF
and need to be addressed by diet therapy. It is important to provide
the CF patient with the optimum diet for the potential for growth to be
fulfilled and resistance to infection maximized.
Energy intake is generally increased by 50% more than the
Recommended Daily Requirement. In order to achieve an adequate energy
intake, effective use should be made of suitable energysupplements such
as glucose polymers and glucose drinks. Fat intake should be normal and
frequent snacks should be encouraged.
Deficiencies of vitamins A, D, E and K are well documented. Daily
supplementation of 8000 IU of vitamin A, 20 mg of vitamin D, and 200 mg
of vitamin E is currently advised. Deficiency of vitamin K has been
noted in patients with liver disease and in young infants with CF. A
supplementation is only necessary if deficiency has been demonstrated.
Lactose Intolerance
Lactose (milk sugar) is digested in the small intestine by the
enzyme lactase. An insufficiency of lactase, in the small intestine,
results in undigested lactose to pass into the large intestine where it
is fermented by bacteria with the production of lactic acid. This
accumulation of lactic acid is characterized by abdominal discomfort,
pain, and diarrhea, the condition known as lactose intolerance.
After the age of 5 the genetic absence of lactase occurs among
remarkably high proportions of Asians (95 percent), Africans (99
percent), American Indians (95 percent), and black Americans (75
percent), as well as among a significant proportion of healthy
Caucasians. The origin of racial lactose intolerance is not entirely
clear. It may be a genetic difference or it may be that the custom of
drinking milk, which is common among Caucasians, results in the
continued production of lactase. Many other races do not take much milk
after infancy, so the enzyme diminishes or disappears completely.
For practical purposes, no differentiation is usually made between
cows milk and goats or sheeps milk. For people who are milk intolerant
a wide range of soya based foods are available.
Nutrition Programs and Services
Food Labels:Evidence related to the role of dietary
factors in gastrointestinal disease suggests that food manufacturers
should include on package labels information about nutrient content of
the food, especially for fat and carbohydrate components (including
fiber).
Food Services:Evidence related to the role of dietary
factors in gastrointestinal diseases suggests that food services should
include provisions for adequate intake of high-fiber and low-fat foods.
Food Products:Evidence related to the role of dietary
factors in gastrointestinal diseases suggests that the public would be
benefit from additional products that are low in fat and calories and
high in fiber. [The Surgeon General's Report on Nutrition & Health, 1988]
