Ch 37: Nutrition

Ch 37: Nutrition

Introduction to Nutrition

Nutrition is the study of nutrients and how they are used by the body for growth, development, activity, reproduction, lactation, health maintenance, and recovery from illness or injury. Essential nutrients must be obtained from the diet because the body cannot synthesize them in sufficient amounts.

• Macronutrients: Supply energy and build tissue (carbohydrates, fats, proteins).

• Micronutrients: Regulate and control body processes (vitamins, minerals).

Six Classes of Nutrients

• Energy-supplying nutrients: Carbohydrates, proteins, lipids (fats).

• Regulatory nutrients: Vitamins, minerals, water.

Energy Balance

Energy Intake and Expenditure

Energy is derived from food and measured in kilocalories (kcal). Only carbohydrates, proteins, and fats provide calories. The balance between energy intake and expenditure determines body weight stability.

• Total daily energy expenditure: Calories used for physical activity, metabolism, and digestion.

• Total daily energy intake: Sum of calories from all foods consumed.

• Weight change: Occurs when intake and expenditure are not equal.

Basal Metabolic Rate (BMR)

BMR is the energy required to fuel involuntary activities of the body at rest after 12 hours. It is influenced by several factors:

• Increases with: Growth, infection, fever, emotional tension, extreme temperatures, elevated hormones.

• Decreases with: Aging, prolonged fasting, sleep.

• Sex differences: Males generally have higher BMR due to greater muscle mass.

Body Mass Index (BMI) and Body Fat Distribution

Body Mass Index (BMI)

BMI is a screening tool to estimate body fat and assess risk for diseases related to overweight and obesity.

• Formula:

$BMI = \frac{\text{weight (kg)}}{\text{height (m)}^2}$

• Interpretation: Higher BMI is associated with increased risk for heart disease, type 2 diabetes, hypertension, and certain cancers.

• Limitations: May be inaccurate for athletes, elderly, and children/teens (different criteria for youth).

Body Fat Distribution

The location of body fat is an important indicator of disease risk. Central (abdominal) obesity is particularly concerning.

• Waist circumference: Risk increases with ≥40 inches (men) or ≥35 inches (women).

• Waist-to-hip ratio (WHR): Used to identify central obesity.

Macronutrients

Carbohydrates

Carbohydrates are organic compounds (carbon, hydrogen, oxygen) that serve as the main energy source for the body.

• Types: Simple (sugars) and complex (starches).

• Sources: Plant-based foods; lactose is the only animal-derived carbohydrate.

• Digestion: Easily and quickly digested; 90% ingested is absorbed.

• Function: Supply energy, especially for the nervous system.

• Recommended intake: 45%–60% of total calories for adults.

• Metabolism: Converted to glucose, transported to the liver, and used or stored as needed.

Proteins

Proteins are vital for the formation of all body structures and are made from 22 amino acids.

• Complete proteins: Contain all essential amino acids (e.g., animal proteins, soy, quinoa).

• Incomplete proteins: Lack one or more essential amino acids (most plant proteins).

• Vegetarian diets: Can combine plant proteins to achieve completeness.

• Digestion: Broken down by pancreatic enzymes; amino acids absorbed and used for new protein synthesis or energy.

• Protein turnover: Constant cycle of breakdown (catabolism) and synthesis (anabolism).

• Recommended Dietary Allowance (RDA): 0.8 g/kg body weight; 10%–35% of total calorie intake.

Example: Red meat is a complete protein source.

Fats (Lipids)

Fats are insoluble in water and blood, composed of carbon, hydrogen, and oxygen. They are the most concentrated energy source in the diet.

• Types: Saturated (raise cholesterol; mostly animal fats) and unsaturated (lower cholesterol; mostly plant fats).

• Triglycerides: Make up 95% of dietary lipids.

• Digestion: Occurs mainly in the small intestine; bile emulsifies fats for enzyme action.

• Absorption: Fats enter lymphatic circulation and are transported to the liver.

• Recommended intake: Saturated fats <10% of daily calories; trans fats as low as possible.

Example: Trans fats are produced when manufacturers partially hydrogenate liquid oils. Trans fats raise serum cholesterol and are found in some processed foods.

Micronutrients

Vitamins

Vitamins are organic compounds required in small amounts for metabolism. They do not provide energy but are essential for the metabolism of carbohydrates, proteins, and fats.

• Water-soluble: Vitamin C, B-complex (not stored in the body).

• Fat-soluble: Vitamins A, D, E, K (stored in body fat).

• Sources: Fresh foods are richer in vitamins than processed foods.

• Absorption: Through the intestinal wall into the bloodstream.

Example: Vitamin A is essential for vision in dim light, skin and mucous membrane health, and immune function.

Minerals

Minerals are inorganic elements found in all body fluids and tissues. They provide structure and help regulate body processes.

• Macrominerals: Calcium, phosphorus, sulfur, sodium, chloride, potassium, magnesium.

• Microminerals (trace elements): Iron, zinc, manganese, chromium, copper, molybdenum, selenium, fluoride, iodine.

• Sources: Present in the ash remaining after digestion.

Water

Water is vital for life, making up 50%–60% of adult body weight. It is the medium for all chemical reactions and is not stored in the body.

• Distribution: Two-thirds intracellular (ICF), one-third extracellular (ECF, including plasma and interstitial fluid).

• Functions: Solvent, aids in digestion, absorption, circulation, and excretion.

Example: Water is more vital to life than food because it is necessary for all chemical reactions and is not stored in the body.

Dietary Guidelines and Assessment

Dietary Guidelines and Tools

• Dietary Guidelines for Americans: Evidence-based recommendations for healthy eating.

• Dietary Reference Intakes (DRIs): Nutrient reference values.

• Recommended Dietary Allowance (RDA): Average daily intake sufficient for most healthy individuals.

• MyPlate: Visual guide for balanced meals.

• Food labeling: Provides nutritional information for consumers.

Factors Affecting Nutrition

• Physiological/Physical: Age, health status, medications.

• Social determinants: Economic stability, healthcare access, education, neighborhood environment.

• Cultural/Religious: Food beliefs, traditions, and aversions.

Developmental Considerations

• Growth periods: Infancy, adolescence, pregnancy, and lactation increase nutritional needs.

• Activity: Increases energy and nutrient requirements.

• Aging: Decreased BMR and caloric needs in adulthood.

Other Influencing Factors

• Sex assigned at birth

• State of health

• Alcohol use disorder

• Medications

• Megadoses of nutrient supplements

Food Choices

• Social determinants of health

• Religion

• Meaning and cultural significance of food

Food Intake

• Decreased intake: Anorexia (lack of appetite)

• Increased intake: Obesity (BMI ≥30)

Nutritional Assessment and Interventions

Components of Nutritional Assessment

• History taking: Dietary, medical, socioeconomic data.

• Physical assessment: Anthropometric and clinical data.

• Biochemical data: Protein status, vitamin, mineral, and trace element levels.

Dietary Data Collection Methods

• 24-hour recall

• Food diaries/calorie counts

• Food frequency records

• Diet history

Nursing Interventions for Nutrition

• Teaching nutritional information

• Monitoring nutritional status

• Stimulating appetite

• Assisting with eating

• Providing oral nutrition

• Providing long-term nutritional support

Therapeutic and Modified Diets

Types of Diets

• Therapeutic diets: Consistent carbohydrate, fat or sodium restricted, high or low fiber, renal.

• Modified consistency diets: Clear liquid, pureed, mechanically altered.

Nutritional Support

Short-Term Nutritional Support

• Nasogastric (NG) or nasointestinal tube feeding

• Confirming tube placement: Radiographic exam, aspirate pH, tube length/marking, CO2 monitoring

Long-Term Nutritional Support

• Enterostomal tube: Gastrostomy or jejunostomy

• Percutaneous endoscopic gastrostomy (PEG) or surgically placed tube

• Preferred for patients unable to eat for extended periods (e.g., comatose)

Enteral Feeding

• Feeding schedules, formulas, and pumps

• Monitor for tolerance and complications (e.g., gastric residual volume)

• Promote safety and comfort

• Provide education

Parenteral Nutrition (PN)

• Contains amino acids, carbohydrates, and lipids

• Highly concentrated, hypertonic solution

• Administered intravenously via central venous access

• Monitor for complications

Complications of Total Parenteral Nutrition (TPN)

• Insertion problems

• Infection and sepsis

• Metabolic alterations

• Fluid, electrolyte, and acid–base imbalances

• Phlebitis

• Hyperlipidemia

• Liver and gallbladder disease

Key Tables

Classification of Nutrients

Nutrient Class	Examples	Main Function
Macronutrients	Carbohydrates, Proteins, Fats	Energy supply, tissue building
Micronutrients	Vitamins, Minerals	Regulate body processes
Water	Water	Solvent, medium for reactions

Types of Fats

Type	Source	Effect on Cholesterol
Saturated	Animal fats	Raises cholesterol
Unsaturated	Vegetable fats	Lowers cholesterol
Trans fat	Partially hydrogenated oils	Raises cholesterol

Macrominerals vs. Microminerals

Type	Examples
Macrominerals	Calcium, Phosphorus, Sulfur, Sodium, Chloride, Potassium, Magnesium
Microminerals	Iron, Zinc, Manganese, Chromium, Copper, Molybdenum, Selenium, Fluoride, Iodine

Additional info: Some explanations and examples have been expanded for clarity and completeness based on standard academic knowledge in nutrition and personal health.