CAIE IGCSE Food and Nutrition (0648) Theory Notes

Food and Nutrition (0648) - Theory Notes

1. Nutritional Terms

1.1 Definitions
  • Diet: The food a person normally eats.
  • Reasons for dieting:
    • Restricting oneself to small amounts or special kinds of food for weight loss.
    • For medicinal reasons.
  • Balanced diet: A diet providing the right amount of nutrients for the needs of an individual.
  • Metabolism: A set of chemical reactions inside the body, controlled by enzymes.
  • Malnutrition: Incorrect or unbalanced intake of nutrients.
  • Undernutrition: Insufficient total intake of nutrients.
  • Overnutrition/Hyperalimentation: A form of malnutrition in which the intake of nutrients is oversupplied.
  • Deficiency diseases: Diseases caused by the lack of specific elements in the diet, usually vitamins or minerals.
  • Nutrition: The process of providing or obtaining the food necessary for health and growth.

2. Nutritive Value of Foods

2.1 Proteins
  • High Biological Value (HBV): Contains all essential amino acids.
    • Sources: Milk, meat, fish, eggs, cheese.
  • Functions:
    • Growth (hair, nails, skin)
    • Body maintenance
    • Repair
  • Symptoms of deficiency:
    • Kwashiorkor: Diarrhoea, fatigue, and an enlarged belly.
    • Marasmus: Growth failure, sunken eyes, an “old man’s” face.
  • Low Biological Value (LBV): Lacks some essential amino acids.
    • Sources: Cereals, pulses, nuts, and some vegetables.
2.2 Carbohydrates
  • Sources: Milk, yogurt, bread, rice, beans, cereals.
  • Classification:
    • Monosaccharides: Cannot be hydrolyzed to simpler carbohydrates (e.g., fructose, glucose, galactose).
    • Disaccharides: Consist of two monosaccharides (e.g., sucrose, maltose, lactose).
    • Polysaccharides: Many glucose molecules joined together (e.g., starch, cellulose, glycogen, dextrin).
  • Functions:
    • Provide energy.
    • Aid in fat metabolism.
    • Help build body mass.
    • Prevent constipation.
  • Chemistry: Composed of oxygen, carbon, and hydrogen.
  • Deficiency: Leads to conditions such as Marasmus, characterized by loss of stamina.
  • Symptoms of Marasmus:
    • Growth failure.
    • Loss of hair.
    • Shrunken body appearance.
    • Ribs sticking out.
    • Skin hang loose.
    • Sunken eyes.
    • “Old man’s” face.
2.3 Fats
  • Sources:
    • Visible fat: Easily detected in food (e.g., butter, cooking oils, fat on meat).
    • Invisible fat: Difficult to detect in food (e.g., lean meat, egg yolk, oily fish, nuts, seeds, fruits, fried foods, sweets).
  • Types:
    • Fats: Solid and saturated.
    • Oils: Liquid and unsaturated.
  • Functions:
    • Provides energy.
    • Stores energy for later use.
    • Protects vital organs.
    • Provides insulation.
    • Adds texture and flavor to foods.
  • Chemistry: Comprised of oxygen, carbon, and hydrogen.
  • Deficiency:
    • Leads to growth failure, eczema of skin, among other issues.
  • Excess consumption: May result in obesity, coronary heart disease (CHD), cancer, high blood pressure, and stress.
2.4 Vitamins
  • Vitamin A:
    • Deficiency: Causes night blindness and skin defects.
    • Sources: Vegetables and fruits, milk, liver, and meats.
    • Functions: Keeps skin and mucus membranes healthy, promotes growth, prevents night blindness.
  • Vitamin B:
    • Deficiency: Results in beri-beri and anaemia.
    • Sources: Eggs, fish, yeast, broccoli, lean meat.
    • Functions: Releases energy from carbohydrates; promotes a healthy nervous system and skin; aids absorption.
  • Vitamin C:
    • Deficiency: Results in scurvy (bleeding gums).
    • Sources: Citrus fruits, berries, and vegetables.
    • Functions: Improves the immune system, aids in wound healing, aids absorption of iron.
  • Vitamin D:
    • Deficiency: Causes rickets (soft bones and dental decay).
    • Sources: Eggs, fish, yeast.
    • Functions: Ensures strong bones and teeth, maintains heart actions, maintains a healthy nervous system.
  • Vitamin E:
    • Deficiency: May lead to sterility.
    • Sources: Cereals and nuts, green vegetables, wheatgerm.
    • Functions: Maintains the reproductive system, aids in fighting diseases.
  • Vitamin K:
    • Deficiency: Leads to prolonged bleeding.
    • Sources: Cabbage, spinach, soybeans, cauliflower.
    • Functions: Essential for blood clotting, aids in maintaining strong bones.
  • B-Group Vitamins:
    • Thiamine (B1):
    • Functions: Supports circulation, blood formation, and brain function.
    • Sources: Organ meats, yeast, peas, beans.
    • Riboflavin (B2):
    • Functions: Important for blood formation and production of antibodies.
    • Sources: Meat, poultry, fish, nuts, liver.
    • Nicotinic acid (B3):
    • Functions: Aids circulation, contributes to healthy skin, supports the nervous system.
    • Sources: Meat, nuts, potatoes.
    • Cobalamin (B12):
    • Functions: Prevents anaemia, promotes cellular longevity, aids digestion.
    • Sources: Lamb, beef, eggs, poultry, liver.
2.6 Minerals
  • Calcium:
    • Deficiency: Leads to osteomalacia and rickets.
    • Functions: Essential for bones and teeth growth, nerve conduction, and muscle contractions.
    • Sources: Yoghurt, milk, cheese, tofu.
  • Iron:
    • Deficiency: Can result in anaemia.
    • Functions: Important for haemoglobin production, helps in micro-nutrient transport.
    • Sources: Liver, soya beans, apricots, leafy vegetables.
  • Phosphorus:
    • Deficiency: May cause anorexia.
    • Functions: Important for metabolism and bone development, contributes to muscle contraction.
    • Sources: Fish, milk, meats, nuts, and poultry.
  • Potassium:
    • Deficiency: Causes hypokalaemia.
    • Functions: Aids nerve impulses and fluid balance, maintains normal heart function.
    • Sources: Potatoes, beans, fruits, vegetables, squash.
  • Sodium:
    • Deficiency: Associated with high blood pressure.
    • Functions: Important for nerve impulse conduction and muscle contraction, regulates fluid balance.
    • Sources: Salt, canned food, meat, fish.
  • Fluoride:
    • Deficiency: Contributes to tooth decay.
    • Functions: Important for the development of bones and teeth, helps teeth resist decay.
    • Sources: Tea, seafood, drinking water.
  • Chloride:
    • Deficiency: Causes an imbalance in blood pH.
    • Functions: Activates salivary amylase, contributes to gastric acidity, regulates osmotic pressure.
    • Sources: Eggs, meat, salt, seaweed, cheese, celery, olives.
  • Iodide:
    • Deficiency: Can cause goitre.
    • Functions: Necessary for hormone production and maintaining metabolic rate.
    • Sources: Yoghurt, milk, eggs, seaweed.
2.7 Water
  • Functions of water:
    • Forms saliva.
    • Regulates body temperature.
    • Flushes body waste (mainly in urine).
    • Prevents constipation.
    • Moistens oxygen for breathing.
    • Helps convert food to energy.
    • Protects body organs and tissues.
    • Lubricates joints.
    • Aids cell growth.
    • Facilitates blood flow.
    • Keeps mucus membranes moist.
    • Helps dissolve minerals and nutrients.
2.8 Non-Starch Polysaccharide (NSP)/ Dietary Fibre
  • Sources and functions of NSP/dietary fibre:
    • Source: Cellulose and pectin.
    • Functions: Cannot be digested, aids in the removal of water from the body via peristalsis, absorbs water.

3. Digestion and Absorption

3.1 Digestion Stages
  • Physical breakdown:
    • Teeth: Rip, tear, and grind food into smaller pieces; however, protein and fat do not break down here.
    • Salivary glands: Produce saliva and amylase to moisten food for easy swallowing.
    • Tongue: Pushes food down the oesophagus.
    • Carbohydrate: Salivary amylase converts starch to maltose.
  • Chemical breakdown:
    • Peristalsis: Moves food around and helps break it down.
    • Chyme: Term referring to broken-down food, which mixes with gastric juices in the stomach.
    • Carbohydrate breakdown: Salivary amylase continues to convert starch to maltose.
3.2 Enzymes in Digestion
  • Amylase: Breaks starch into maltose.
  • Erepsin: Digests peptones into amino acids (found in intestinal juices).
  • Invertase: Breaks sucrose into glucose and fructose.
  • Lactase: Breaks lactose into glucose and galactose.
  • Lipase: Breaks down fats (found in pancreatic juices/intestines).
  • Maltase: Breaks maltose into glucose.
  • Pepsin: Breaks proteins into peptides, then into peptones, subsequently into polypeptides.
  • Renin: Clots milk.
  • Trypsinogen: Breaks proteins into peptones.
3.3 Role of Bile in Fat Emulsification
  • Liver: Produces bile, which emulsifies fats by breaking them down into small droplets.
  • Function of bile: Increases surface area for digestion by lipase.
3.4 Absorption of Nutrients
  • Small intestine:
    • Note: Alcohol is the only substance that can be absorbed in the stomach.
    • Villi: Tiny, finger-like projections surrounded by single cells that allow nutrients to move through and reach the lacteal.
    • Lacteal: Connected to the lymphatic system, surrounded by blood capillaries.
    • Absorption: Monosaccharides, amino acids, water-soluble vitamins, and minerals are absorbed into blood capillaries.
    • Glucose: Used for immediate energy or converted to glycogen, which is stored in the liver and muscles.
    • Glycerol and fatty acids: Absorbed into the lacteal and converted to soluble fats in the liver.
  • Large intestine:
    • Food residues and liquid waste pass through, where water is absorbed, transforming residues into solid feces.
    • Non-starch polysaccharide (NSP) aids in all actions here.

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