Download Nutritional diseases

Nutritional diseases
2014-2015
A healthy diet provides :
(1) sufficient energy, in the form of carbohydrates, fats, and proteins, for the body’s
daily metabolic needs
(2) essential (as well as nonessential) amino acids and fatty acids, used as building
blocks for synthesis of structural and functional proteins and lipids;
(3) vitamins and minerals, which function as coenzymes or hormones in vital
metabolic pathways or, as in the case of calcium and phosphate, as important
structural components.
In primary malnutrition, one or all of these components are missing from the diet.
By contrast, in secondary, malnutrition, the dietary intake of nutrients is adequate,
and malnutrition results from nutrient malabsorption, impaired utilization or storage,
excess losses, or increased requirements.
The causes of secondary malnutrition can be grouped into three general but
overlapping categories: GI diseases, chronic wasting diseases, and acute critical
illness.
Some common causes of dietary insufficiencies are listed here:
1. Poverty. Homeless people, elderly persons, and children of the poor often
suffer from protein-energy malnutrition (PEM) as well as trace nutrient
deficiencies.
2. Ignorance. Even the rich may fail to recognize that infants, adolescents, and
pregnant women have increased nutritional needs. Ignorance about the
nutritional content of various foods also contributes to malnutrition, e.g. iron
deficiency often develops in infants fed exclusively artificial milk diets; and
iodine often is lacking from food and water in regions removed from the
oceans, unless supplementation is provided.
3. Chronic alcoholism. Alcoholic persons may sometimes suffer from PEM but
are more frequently lacking in several vitamins, especially thiamine,
pyridoxine, folate,and vitamin A
4. Acute and chronic illnesses. The basal metabolic rate becomes accelerated
in many illnesses (in patients with extensive burns, it may double), resulting
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Nutritional diseases
2014-2015
in increased daily requirements for all nutrients. Failure to recognize these
nutritional needs may delay recovery. PEM is often present in patients with
metastatic cancers.
5. Self-imposed dietary restriction. Anorexia nervosa, bulimia, and less overt
eating disorders affect a large population of persons who are concerned about
body image or suffer from an unreasonable fear of cardiovascular disease
Protein-Energy Malnutrition
Protein-energy malnutrition (PEM) is characterized by inadequate dietary intake of
protein and calories (or malabsorption) with resultant muscle, fat, and weight loss,
lethargy, and generalized weakness.
A body-mass index less than 16 kg/m2 constitutes malnutrition; body mass index
(BMI) is defined as weight (kg)/height2 (m2), where normal (18.5-25) kg/m2. More
practically, a child whose weight falls to less than 80% of normal is considered to
be malnourished. Other helpful measures are fat stores, muscle mass, and circulating
levels of serum proteins (e.g., albumin and transferrin).
Marasmus and Kwashiorkor
Marasmus and kwashiorkor are two ends of the PEM spectrum but also have
substantial overlap:
Marasmus:
1. Weight loss of 60% or more compared to normal for sex and age
2. Growth retardation and loss of muscle mass
3. Protein and fat are mobilized from the somatic compartment of the body
(largely skeletal muscle and subcutaneous fat); this provides energy from
amino acids and triglycerides
4. Serum protein levels are largely maintained
5. Diminished leptin synthesis may drive increased pituitary-adrenal axis
production of glucocorticoids that induce lipolysis
6. Anemia and immune deficiency are common, with recurrent infections
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Nutritional diseases
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Kwashiokor:
1. Occurs when protein deprivation is relatively greater than overall calorie
reduction
2. Associated with protein loss from the visceral compartment of the body
(largely liver); there is relative sparing of muscle and adipose tissue
3. Resulting hypoalbuminemia causes generalized edema that may mask weight
loss
4. An enlarged fatty liver is due to inadequate lipoprotein synthesis and thus
hepatic accumulation of peripherally mobilized triglycerides
5. Apathy, listlessness, and anorexia occur
6. Small bowel mucosal atrophy (reversible) can lead to malabosrption
7. Immune deficiency is common, with secondary infections
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