Nutrition and Metabolism

Altered Nutrition

• It can be caused by inadequate or excessive digestion, absorption, transportation, or metabolism of nutrients.
• Undernutrition and overnutrition are two categories.

Causes of Altered Nutrition

• Genetic defects that impact metabolism or nutrient absorption
• Malformation or damage to the Gl mucosa
• Inadequate or excessive dietary intake
• Excessive nutrient losses such as vomiting, diarrhea, or laxative use
• Hypermetabolic states due to hyperthyroidism, cancer, burns, fever, or severe infection
• Malabsorptive syndromes.
• Ingestion of unsafe food and water

Genetic Defects

• Most often related to errors in amino acid and lipid metabolism
• Commonly a genetically-based defect in enzyme activity

Catabolic-Anabolic Steady State

• Blood concentrations of energy sources are equalized between the absorptive and postabsorptive states.
• Absorptive state: lasts four hours after each meal, nutrient absorption occurs, and anabolism exceeds catabolism.
• Postabsorptive state: Gl tract is empty, energy sources supplied by breakdown of reserves, catabolism exceeds anabolism, and blood glucose is maintained between meals.

Absorptive State Hormonal Control

• Primarily controlled by insulin.
• Insulin secretion stimulation by elevated blood levels of glucose and amino acids, intestinal hormone (glucose-dependent insulinotropic peptide (GIP)), and parasympathetic stimulation.

Diabetes Mellitus

• A group of disorders characterized by the inability to regulate glucose levels, leading to inadequate metabolism of protein, fats, and carbohydrates
• Pathophysiology is characterized by the destruction of pancreatic beta cells and/or impaired beta cell function, and/or peripheral resistance to insulin.
• Glucose is unavailable to most body cells, resulting in hyperglycemia.
• Cells, such as liver, muscle, and adipose cells, become deprived of glucose as an energy source.
• Body uses less efficient available sources, such as body fats and proteins, for energy.
• Clinical manifestations include weight loss, hunger, polyphagia, polyuria, polydipsia, circulatory failure, metabolic acidosis, CNS depression, and coma.

Postabsorptive State

• Regulation is complex, involving the sympathetic nervous system interacting with several hormones
• A reduced release of insulin as blood glucose levels drop triggers the postabsorptive state.
• Glucagon is a hyperglycemic hormone released due to declining blood glucose and rising amino acid levels.
• Glucagon promotes glycogenolysis and gluconeogenesis in the liver.
• Glucagon promotes lipolysis in adipose tissue which releases fatty acids and glycerol into blood
• Glucagon modulates glucose effects after a high-protein, low-carbohydrate meal

Undernutrition

• Lack of nutrient intake.
• Inadequate macronutrient and micronutrient consumption
• Common problems: protein, iron, and vitamins inadequately consumed or in great demand
• Can lead to weight loss, muscle wasting due to use of muscle mass and adipose energy stores
• Severe or prolonged illness can affect cardiac and respiratory muscle function.
• High risk for elderly in nursing homes due to poor appetite, alterations in taste, problems with swallowing, limited income, inadequate social support, and physical mobility limitations.
• Deficiencies in vitamins and minerals depend upon role of deficient substance

Protein-Energy Malnutrition

• Depletion of body's lean tissues can be triggered by starvation, or a combination of starvation and catabolic stress
• Has high prevalence among children in underdeveloped countries due to food deprivation

Marasmus

• Protein and energy deficiency: progressive loss of muscle/fat stores due to inadequate food intake, equally deficient in calories/protein

Kwashiorkor

• Protein deficiency: deficiency in protein despite high carbohydrate diets

Protein-Energy Malnutrition in Industrialized Societies

• Can occur due to trauma or illness.
• Includes Marasmus-like secondary protein-energy malnutrition from chronic illnesses and Kwashiorkor-like malnutrition from hypermetabolic acute illnesses.
• Marasmus-like is caused by chronic illnesses like chronic obstructive pulmonary disease, congestive heart failure, cancer, HIV infection
• Kwashiorkor-like is caused by hypermetabolic acute illnesses such as trauma, burns, sepsis

Marasmus Details

• Overall lack of nutrients leading to weight loss
• Wasting of muscle and subcutaneous tissue causes a resemblance to a living skeleton.
• Often occurs under age of two, where immune system is too weak to fight off mild viral infections.

Kwashiorkor Details

• Occurs even with sufficient calories if protein intake is low.
• A switch from protein-rich breast milk to protein-poor food can trigger the condition.
• Children's bellies swell with filtered fluid (ascites) due to a lack of plasma proteins.
• Decreased plasma proteins causes osmosis, which pulls water from blood into the peritoneal space.
• The immune system becomes depleted of antibodies and individuals are prone to infection.
• Individuals require increased calorie and protein intake.

Starvation

• Healthy humans can typically survive 50-70 days without food.
• Can be caused by hunger strikes, imprisonment, or psychological eating disorders like anorexia and bulimia.

Malabsorption

• Lack of movement of one or more nutrients across the gastrointestinal mucosa
• Types include a single nutrient deficiency, multiple nutrients at one segment and multiple nutrients deficiency along the entire intestinal mucosa length
• Fat and fat-soluble substances are almost always included in the malabsorption syndrome.
• Can be caused by processing/digestion problems, substance-moving problems, and lymphatic obstruction
• Difficultly breaking down food into its constituent building blocks, such as with pancreatitis with loss of digestive enzymes

Overnutrition

• Excessive consumption of nutrients.
• Includes excessive caloric intake leading to obesity and vitamin/mineral toxicity which depends upon the role of the vitamin or mineral.

General Manifestations of Altered Nutrition

• Cells and body tissues rely on adequate nutrition for functioning.
• Undernutrition: weight loss, muscle wasting, muscle weakness, dehydration, fatigue, vitamin deficiencies, etc...
• Malabsorption: rapid transit of nutrients, can result in greasy stool, diarrhea, bloating, etc...
• Overnutrition/Excessive nutrient intake: potential toxicity

Diagnostic and Treatment Strategies

• Diagnostic tests: Nutritional assessment, Body mass index, Basal metabolic rate, Laboratory evaluation, Blood tests, Urine tests, Stool samples, Biopsy, etc..
• Treatment: Dietary intervention, Medications, etc..