Ch_18-_Nutrition__Metabolism__2024_

Nutrition & Metabolism Overview

• Chapter 18 discuss the role of nutrients and metabolism in the human body.

Introduction to Nutrients

• Nutrients: Chemicals from the environment needed for survival.

  • Supply energy for metabolic processes.

  • Serve as building blocks for bodily molecules.

• Types of Nutrients:

  • Macronutrients: Required in large quantities (e.g., carbohydrates).

  • Micronutrients: Required in small amounts (e.g., vitamins).

• Essential Nutrients: Cannot be synthesized enough by the body; must be obtained from food sources.

Carbohydrates (18.1)

• Definition: Organic compounds made up of carbon, hydrogen, and oxygen (CH2O)n.

• Categories:

  • Complex Carbohydrates (Polysaccharides): Many sugars, e.g., starch from plants, glycogen from meats.

  • Simple Carbohydrates:

    • Disaccharides (double sugars): E.g., milk sugar, cane sugar.

    • Monosaccharides (single sugars): E.g., glucose, fructose from honey and fruit.

• Energy Storage:

  • Glycogenesis: Excess glucose stored as glycogen in liver and muscle cells.

  • Lipogenesis: Excess glucose converted to fat when glycogen stores are full.

  • Respiration Process: Glucose is broken down into CO2, H2O, and energy.

Lipids (18.2)

• Definition: Organic compounds including fats, oils, phospholipids, and cholesterol.

• Energy Content: Fats provide more than double the energy per gram compared to carbohydrates and proteins.

• Lipid Types:

  • Saturated Fats: Found in animal products; contain only single bonds between carbon atoms; linked to heart disease.

  • Unsaturated Fats: Found in plant oils, nuts; contain one or more double bonds.

• Cholesterol: Present in liver and egg yolk, not found in plant sources.

• Essential Fatty Acids: Cannot be produced by the body; must be included in the diet.

Proteins (18.3)

• Components: Made of amino acids; 21 total amino acids used in protein formation.

• Functions:

  • Structural and hormonal roles.

• Energy Source: Proteins can serve as energy after being broken down into amino acids; process involves deamination.

• Sources: Meats, fish, dairy, nuts, legumes.

• Amino Acids:

  • Essential Amino Acids: Cannot be synthesized; must be obtained from food.

  • Non-Essential Amino Acids: Can be synthesized by the body.

• Protein Quality:

  • Complete Proteins: Contain all essential amino acids; mostly from animal sources.

  • Incomplete Proteins: Lack one or more essential amino acids; commonly found in plants.

Energy Expenditures (18.4)

• Definition: Carbs, fats, and proteins provide energy for metabolic processes.

• Caloric Content:

  • A calorie measures potential energy in food; capital "C" indicates nutritional Calories (1,000 heat calories).

• Basal Metabolic Rate (BMR):

  • Energy used by the body at rest after overnight fasting.

  • Influenced by gender, body size, temperature, and thyroid hormone levels.

• Energy Requirements: Needed for BMR, muscular activity, growth, and body temperature maintenance.

• Energy Balance:

  • Positive Energy Balance: Caloric intake exceeds output, leading to weight gain.

  • Negative Energy Balance: Caloric expenditure exceeds intake, leading to weight loss.

• Body Mass Index (BMI): Tool to assess weight relative to height, classifying individuals as underweight, normal, or obese.

Vitamins (18.6)

• Definition: Organic compounds necessary in small amounts for metabolism; cannot be synthesized in adequate amounts by the body.

• Types:

  • Fat-Soluble: A, D, E, K; stored in tissues; risks of overdose.

  • Water-Soluble: B vitamins and C; excess usually excreted.

• Vitamin Misconceptions:

  • Higher amounts of vitamins do not guarantee better health.

  • Many individuals benefit from supplements (especially pregnant women).

Minerals (18.7)

• Definition: Inorganic elements required for metabolic functions; sourced from soil via plants.

• Major Minerals: Include calcium, phosphorus, potassium, sodium, etc.; essential for various bodily functions like muscle contraction and nerve impulses.

• Trace Elements: Minor components needed in very small amounts (e.g., iron, zinc).

Healthy Eating (18.8)

• Adequate Diet: Ensures energy needs, essential fatty acids, amino acids, and vitamins/minerals are met.

• Dietary Guidelines: Use RDA and concepts like MyPlate for balanced nutrition.

• Malnutrition Types:

  • Undernutrition: Deficiency of essential nutrients.

  • Overnutrition: Excess nutrient intake.

• Nutritional Disorders: Include obesity and related diseases, influenced by dietary habits and genetics.

Life-Span Changes (18.9)

• Metabolic Needs: BMR fluctuates through life, increasing during childhood, peaking in adolescence, and declining in adulthood.

• Social and Economic Factors: Diet often reflects medical conditions and socio-economic status.