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Nutrition

Subject: Biology
Topic: 6
Cambridge Code: 0610 / 0970 / 5090

Nutrient Classes​

Nutrition - Taking in and using food for growth, energy, repair

Macronutrients​

Carbohydrates - Energy source

  • Simple sugars (glucose)
  • Complex (starch, cellulose)
  • ~17 kJ per gram

Proteins - Growth, repair, structure

  • Amino acid sources
  • ~17 kJ per gram
  • Essential amino acids (9)

Lipids (Fats) - Energy, structure, insulation

  • ~39 kJ per gram
  • Saturated vs unsaturated

Water - Transport medium, cooling, reactions

  • 60-70% body mass
  • Dissolves nutrients

Micronutrients​

Minerals - Specific functions Vitamins - Enzyme co-factors

Energy Requirements​

Daily energy requirement=Basal metabolic rate+Activity level\text{Daily energy requirement} = \text{Basal metabolic rate} + \text{Activity level}

Basal Metabolic Rate (BMR)​

Energy needed at rest for:

  • Breathing
  • Heartbeat
  • Kidney function
  • Body temperature maintenance

Factors Affecting Requirements​

  • Age: Growing children need more
  • Sex: Males typically need more
  • Activity level: Athletes need more
  • Climate: Cold climates need more
  • Health: Illness increases need

Minerals and Vitamins​

Minerals​

Calcium: Bone structure, muscle contraction

  • Sources: Milk, cheese, green vegetables
  • Deficiency: Weak bones, rickets

Iron: Hemoglobin (oxygen transport)

  • Sources: Red meat, spinach, beans
  • Deficiency: Anemia

Iodine: Thyroid hormone production

  • Sources: Iodized salt, sea fish
  • Deficiency: Goiter, growth problems

Phosphorus: Bone structure, ATP

  • Sources: Meat, fish, nuts
  • Deficiency: Weak bones

Vitamins​

Vitamin A: Vision, skin, immunity

  • Sources: Carrots, sweet potato, liver
  • Deficiency: Night blindness

Vitamin C: Collagen synthesis, immunity

  • Sources: Citrus, berries, peppers
  • Deficiency: Scurvy (poor wound healing)

Vitamin D: Calcium absorption

  • Sources: Sunlight, fatty fish, eggs
  • Deficiency: Rickets (weak bones)

Vitamin B complex: Energy metabolism

  • Sources: Whole grains, meat, legumes
  • Deficiency: Various (beriberi, pellagra)

Balanced Diet​

Balanced diet - Contains correct proportions of nutrients

Food Groups​

  • Carbohydrates - 45-65% of energy
  • Proteins - 10-35% of energy
  • Fats - 20-35% of energy
  • Minerals and vitamins - Small amounts
  • Fiber - 25-30 grams per day
  • Water - 1.5-2 liters per day

Dietary Guidelines​

  • Variety of foods
  • Appropriate portion sizes
  • Limit added sugars (less than 25g for women, less than 36g for men)
  • Limit salt (less than 5g per day)
  • Limit saturated fat (less than 10% of energy)

Malnutrition​

Malnutrition - Insufficient or excessive nutrients

Undernutrition​

Protein-Energy Malnutrition (PEM):

  • Insufficient calories and protein
  • Results: Kwashiorkor, marasmus

Kwashiorkor: Protein deficiency

  • Signs: Swollen abdomen, hair color change
  • Cause: Inadequate protein with calories

Marasmus: Energy deficiency

  • Signs: Wasting, weak muscles
  • Cause: Insufficient food overall

Overnutrition​

Obesity: Excessive energy intake

  • BMI > 30
  • Risks: Diabetes, heart disease
  • Causes: Excess calories, sedentary lifestyle

Micronutrient Deficiencies​

Scurvy: Vitamin C deficiency Rickets: Vitamin D/Calcium deficiency Anemia: Iron deficiency Goiter: Iodine deficiency

Special Dietary Needs​

Vegetarian/Vegan:

  • All proteins needed
  • B12 supplementation for vegans
  • Iron from plant sources (legumes, fortified)

Diabetes:

  • Control carbohydrate intake
  • Low glycemic index foods
  • Limited simple sugars

Celiac:

  • Avoid gluten (wheat, barley, rye)
  • Gluten-free alternatives

Food Preservation​

Methods preserve nutrients, prevent spoilage:

  • Freezing - Stops bacterial growth
  • Canning - Heat kills bacteria
  • Drying - Removes water
  • Salting - Osmotic dehydration
  • Smoking - Antimicrobial compounds
  • Pasteurization - Heat treatment

Key Points​

  1. Macronutrients: carbohydrate, protein, lipid
  2. Micronutrients: minerals, vitamins
  3. Balanced diet has all nutrients
  4. Minerals and vitamins prevent deficiency
  5. Energy requirements vary by person
  6. Malnutrition: under or over nutrition

Practice Questions​

  1. List essential minerals and functions
  2. Describe vitamin deficiency effects
  3. Calculate daily energy requirements
  4. Design balanced meal plans
  5. Compare kwashiorkor and marasmus
  6. Explain special dietary needs

Revision Tips​

  • Learn mineral and vitamin functions/sources
  • Know deficiency symptoms
  • Understand balanced diet composition
  • Practice energy calculations
  • Know malnutrition types
  • Understand special dietary requirements