PRELIMS

Human Nutrients: Carbohydrates, Proteins, and Fats

Nutrients provide energy and materials for the biosynthesis and growth of the body.

0. Macronutrients vs Micronutrients

• Macronutrients: Required in large quantities; provide energy — Carbohydrates, Proteins, Fats (and water).
• Micronutrients: Required in trace quantities; do not provide energy but regulate metabolism — Vitamins and Minerals.
• Roughage (Dietary Fibre): Indigestible plant material (cellulose); adds bulk to food, aids peristalsis and prevents constipation, though it provides no nutritive value itself.

I. Carbohydrates: The Immediate Energy Source

Organic compounds with a C:H:O ratio of 1:2:1. Provide 50–75% of total energy.

• Energy: 1g Glucose = 4.2 kcal.
• Classification:
  1. Monosaccharides: Simple sugars (e.g., Glucose, Triose).
  2. Oligosaccharides: 2–10 monosaccharides (e.g., Maltose, Sucrose, Lactose).
  3. Polysaccharides: Long chains; insoluble (e.g., Starch, Glycogen, Cellulose, Chitin).
• Sources: Wheat, rice, maize, potato.

II. Proteins: The Building Blocks

Complex organic compounds made of 20 types of amino acids. Discovered by Berzelius. Make up ~15% of the human body.

• Essential Amino Acids: 10 acids must be obtained through food (12 synthesized by the body).
• Types: Simple (Albumin), Conjugated (Chromoprotein), Derived (Peptones).
• Functions: Cell formation, physical growth, and genetic character development.
• Deficiency Diseases (in Children):
  1. Kwashiorkor: Thin limbs and a protruding stomach.
  2. Marasmus: Muscles are loosened; general wasting.

III. Fats: Concentrated Energy

Esters of glycerol and fatty acids; insoluble in water.

• Energy: 1g Fat = 9.3 kcal.
• Forms: Solid at 20°C (Fat), Liquid at 20°C (Oil).
• Fatty Acids:
  1. Saturated: Coconut/Palm oil (Bad for heart in excess).
  2. Unsaturated: Fish oil and vegetable oils.
• Functions: Insulates body heat, tastes food, and protects internal organs.

IV. Daily Nutritional Requirements

• Light Worker: ~2000–2100 kcal
• 8-Hour Worker: ~2500–3000 kcal
• Hard Worker: ~3000–3600 kcal

UPSC Relevance

Nutrition science is critical for Public Health and Social Development.

• Energetics: Identifying Fats as having the highest energy density (9.3 kcal/g) compared to Carbohydrates (4.2 kcal/g).
• Public health: Linking protein deficiency to Kwashiorkor and Marasmus in the context of malnutrition.
• Dietary fats: Understanding the health benefits of Unsaturated fats over Saturated fats for heart health.