Human Nutrition Notes

Introduction to Human Nutrition
Humans require various nutrients to survive, and a balanced diet is essential for obtaining these nutrients. A balanced diet consists of all food groups in the correct proportions.

Essential Nutrients

1. Carbohydrates

   • Function: Provide energy for cellular respiration.

   • Sources: Rice, pasta, potatoes.

2. Fats and Oils

   • Function: Serve as long-term energy stores and provide insulation(protection).

   • Sources: Cheese, fatty meats, butter.

3. Proteins

   • Function: Vital for growth and repair of tissues.

   • Sources: Fish, meat, eggs.

4. Vitamins

   • Vitamin C:

     • Function: Maintains healthy skin and gums.

     • Deficiency: Causes scurvy, leading to poor wound healing and excessive bleeding.

     • Sources: Citrus fruits (oranges, lemons).

   • Vitamin D:

     • Function: Helps absorb calcium for strong bones and teeth.

     • Deficiency: Leads to rickets, causing weak bones.

     • Sources: Dairy products, fish oil, eggs.

5. Minerals

   • Calcium:

     • Function: Essential for strong bones and teeth; aids in blood clotting.

     • Sources: Milk, cheese, eggs.

   • Iron:

     • Function: Necessary for hemoglobin in red blood cells, which carries oxygen.

     • Sources: Red meat, spinach.

6. Fiber (Roughage)

   • Function: Aids in moving food through the digestive system.

   • Sources: Vegetables, fruits, whole grains.

7. Water

   • Function: Required for chemical reactions in cells.

   • Sources: Plain water, beverages, and food.

The Digestive System

The digestive system breaks down food into smaller molecules for nutrient absorption. It consists of several organs:

• Mouth

• Esophagus

• Stomach

• Small Intestine (includes duodenum and ileum)

• Large Intestine (includes colon, rectum, anus)

Associated Organs:

• Salivary glands

• Pancreas

• Liver

• Gall bladder

Functions of the Digestive System

1. Ingestion:

   • Taking food and drink into the body.

2. Digestion:

   • Breakdown of food into smaller, absorbable molecules.

   • Types of Digestion:

     • Physical Digestion: Mechanical breakdown (e.g., chewing).

     • Chemical Digestion: Enzymatic breakdown of food molecules.

3. Absorption:

   • Movement of nutrients from the intestines into the bloodstream.

4. Assimilation:

   • Uptake and use of nutrients by cells.

5. Ejection:

   • Removal of undigested food as feces.

Physical and Chemical Digestion

• Physical Digestion:

  • Involves breaking food into smaller pieces without changing its chemical structure.

  • Processes:

    • Chewing in the mouth.

    • Stomach mixing food with digestive juices.

• Chemical Digestion:

  • Breakdown of large molecules into smaller, soluble molecules through enzymes.

  • Key Enzymes:

    • Amylase: Breaks down starch into sugars (acts in the mouth and duodenum).

    • Protease: Breaks down proteins into amino acids (active in the stomach and small intestine).

    • Lipase: Breaks down fats into fatty acids and glycerol (acts in the duodenum).

Role of Enzymes in Digestion

• Amylase:

  • Converts starch to maltose, then maltose to glucose.

• Protease (Pepsin & Trypsin):

  • Pepsin works in the stomach; trypsin works in the small intestine, both breaking down proteins into amino acids.

• Lipase:

  • Converts fats into fatty acids and glycerol.

Role of Hydrochloric Acid and Bile

• Hydrochloric Acid:

  • Found in gastric juice; kills harmful microorganisms and provides an acidic environment for enzyme activity.

• Bile:

  • Produced by the liver, stored in the gall bladder, and released into the duodenum.

  • Functions:

    • Emulsifies fats, breaking them down into smaller droplets for easier digestion.

    • Neutralizes stomach acid to create a suitable pH for enzymes in the small intestine.

Absorption in the Small Intestine

• Structure of the Ileum:

  • Highly folded surface with millions of villi and microvilli, increasing surface area for absorption.

• Villi Functions:

  • Contain capillaries that absorb glucose and amino acids, transporting them into the bloodstream.

  • Lacteals absorb fatty acids and glycerol, transporting them into the lymphatic system.

Conclusion

Understanding human nutrition is vital for maintaining health and well-being. A balanced diet, rich in essential nutrients, supports bodily functions and promotes overall health. The digestive system plays a crucial role in breaking down food and absorbing nutrients, aided by enzymes and digestive juices.

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