Nutrition in Humans

Diet and Energy Needs

• Diet: The food consumed by an animal daily, influenced by age, sex, and lifestyle. Balanced diets provide necessary nutrients.

• Energy Usage: Daily energy requirement varies; individuals become tired if they consume too little energy. Cumulative energy is stored as fat when overconsumed and utilized when underconsumed.

• Balanced Diet: Contains all essential nutrients in appropriate proportions: carbohydrates, proteins, fats, vitamins, minerals, and water, along with dietary fiber.

Nutrients

Carbohydrates

• Function: Main energy source.

• Types: Includes starch and sugar; staple foods rich in starch are potatoes, wheat, rice, and maize.

Fats and Oils

• Function: Energy storage and cellular membrane construction. Acts as insulation and provides protection to organs.

• Sources: Found in cooking oils, meat, dairy products, and oily fish.

Proteins

• Function: Essential for growth and tissue repair; includes enzymes and hormones.

• Sources: Meat, fish, dairy products, eggs, nuts, and legumes.

Vitamins and Minerals

Vitamins

• Definition: Organic compounds required in small amounts.

• Example:

  • Vitamin C (found in citrus fruits) aids collagen production; its deficiency leads to scurvy (gums bleeding).

  • Vitamin D (from sunlight or foods) aids calcium absorption; inadequacy results in rickets.

Minerals

• Definition: Inorganic substances needed in tiny quantities.

• Key Examples:

  • Iron: Vital for hemoglobin; sourced from red meat, beans; deficiency results in anemia.

  • Calcium: Important for bone health; sourced from dairy; deficiency results in brittle bones.

Importance of Water and Fiber

Water

• Makes up over 60% of the body; fundamental for physiological processes and nutrient transport.

Fiber

• Essential for digestive health; aids in peristalsis (the muscular movement in the digestive tract) and prevents constipation. Found in fruits, vegetables, and whole grains.

Human Digestive System

Anatomy

• Comprised of the alimentary canal (mouth, esophagus, stomach, intestines) and accessory organs (liver, pancreas).

Digestive Process

1. Ingestion: Taking in food.

2. Digestion: Physical (mechanical breakdown) and chemical breakdown (using enzymes).

3. Absorption: Nutrients move into the bloodstream through the intestinal walls.

4. Egestion: Unabsorbed materials are expelled from the body.

Roles of Digestive Organs

Mouth

• Begins digestion with mechanical breakdown by teeth and enzymatic action of saliva (amylase).

Stomach

• Stores food for mixing with gastric juices, initiating protein digestion via pepsin in a highly acidic environment.

Small Intestine

• Major site for nutrient absorption. Has folds called villi that increase surface area to maximize absorption.

• Enzymes like lipase, amylase, and proteases are secreted to aid nutrient breakdown.

Large Intestine

• Absorbs remaining water and stores waste until elimination.

Summary of Digestion

• Physical Digestion: Mechanical breakdown of food for easier enzymatic action.

• Chemical Digestion: Breakdown of macromolecules into absorbable units (glucose, amino acids, fatty acids) by specific enzymes.

• Absorption: Utilization of nutrients, facilitated by the extensive surface area provided by villi and microvilli in the small intestine.