Learning Outcomes

• Role of Nutrition in Disease

  • Understand the role of nutrition in disease prevention and management.

  • Recognize specific nutrition-related diseases (scurvy, rickets, etc.).

• Macronutrients Overview

  • Familiarize with basic structural features and roles of:

    • Carbohydrates

    • Fats

    • Proteins

• Digestion and Absorption

  • Explain carbohydrate, fat, and protein digestion and absorption processes.

• Glycemic Index (GI)

  • Define GI and its effects on blood glucose levels.

• Amino Acids

  • Recognize essential amino acids.

Nutrition and Dietary Related Diseases

• Historical Insight

  • Single nutrient treatments contributed to understanding nutrition's role in health.

  • Example diseases:

    • Scurvy: Vitamin C deficiency

    • Beri Beri: Thiamin deficiency

    • Goitre: Iodine deficiency

    • Anaemia: Iron deficiency

    • Rickets: Vitamin D deficiency

Nutrient Classification

• Macronutrients vs Micronutrients

  • Macronutrients (required in larger amounts):

    • Carbohydrates

    • Fats

    • Proteins

  • Micronutrients (required in smaller amounts):

    • Minerals (e.g., Calcium, Phosphorus)

    • Vitamins (water-soluble & fat-soluble)

Carbohydrates

• Types of Carbohydrates

  • Monosaccharides:

    • Simple sugars (4-6 carbons) like glucose, fructose, galactose.

  • Disaccharides:

    • Two monosaccharides (e.g., sucrose, lactose, maltose).

  • Oligosaccharides:

    • Fewer than 10 units; non-absorbed, fermented in the colon.

  • Polysaccharides:

    • More than 10 monosaccharides (e.g., starches, cellulose).

    • Starch Types:

      • Amylose: straight chains linked by α-1,4-glycosidic bonds.

      • Amylopectin: branched chains with α-1,6-glycosidic bonds.

Carbohydrate Digestion and Absorption

• Process:

  • Monosaccharides: Absorbed in the small intestine (SI) without digestion.

  • Disaccharides: Enzymatically broken down to monosaccharides in SI.

  • Starch:

    • Salivary amylase acts in mouth.

    • Pancreatic amylase further breaks down starch in the duodenum.

  • Transport Mechanism:

    • Glucose and galactose absorbed via SGLT1 and transported into blood.

Glycemic Effects and Index of Carbohydrates

• Glycemic Index (GI):

  • Measures blood glucose increase post-carb intake.

  • Foods categorized by GI:

    • High (>85): e.g., white bread, potatoes.

    • Moderate (60-85): e.g., pasta, porridge.

    • Low (<60): e.g., apples, beans.

Non Glycaemic Effects of Carbohydrates

• Health Benefits:

  • Non-starch polysaccharides promote chewing, increasing saliva flow.

  • Soluble fiber nourishes gut microbiota, aiding colon health.

  • Insoluble fiber increases stool mass and promotes bowel regularity.

Fats (Lipids)

• Essential Roles:

  • Provide energy, insulation, and structural components.

  • Types:

    • Triacylglycerols: Three fatty acids and glycerol.

    • Phospholipids: Two fatty acids, glycerol, phosphate.

    • Sterols: Ring-structured lipids (e.g., cholesterol).

Structure of Fats

• Fatty Acids:

  • Saturated, monounsaturated, polyunsaturated types.

  • Saturated: No double bonds; solid at room temperature.

  • Monounsaturated: One double bond (e.g., olive oil).

  • Polyunsaturated: At least two double bonds (e.g., omega-3s).

• Trans Fatty Acids:

  • Linked with negative health implications; found in processed foods.

Fat Digestion and Absorption

• Process:

  1. Stomach breaks down large fat particles.

  2. Bile emulsifies fats in the duodenum.

  3. Pancreatic lipase breaks down fats into fatty acids and glycerol.

  4. Fatty acids absorbed in the small intestine.

Fat Transport

• Lipoproteins:

  • Transport fats in blood:

    • Chylomicrons: Carry dietary fats.

    • VLDLs, LDLs, HDLs: Transport resynthesized TAGs and cholesterol, respectively.

Fat Storage

• Adipose Tissue:

  • Fat stored as a single droplet in white adipose cells.

  • Brown adipose tissue involved in thermogenesis.

Proteins

• Functions and Structure:

  • Building blocks of life, enzymes, and hormones.

  • Composed of amino acids linked by peptide bonds.

• Essential Amino Acids:

  • Nine amino acids cannot be synthesized by the body; need to be obtained from diet.

Protein Digestion and Absorption

• Process:

  1. Starts in the mouth (chewing) and continues in the stomach (pepsin action).

  2. Continues in the duodenum (trypsin and chymotrypsin activity).

  3. Absorption mainly occurs via active transport mechanisms or passive diffusion.

Functions of Proteins

• Synthesis and Turnover:

  • Energy-demanding process; constant turnover between synthesis and breakdown.

• Amino Acid Derivatives:

  • Various amino acids have specific functions (e.g., neurotransmitter synthesis).