Introduction to Micronutrients and Water

Welcome! In our previous lessons, we looked at macronutrients like carbohydrates, proteins, and lipids, which our bodies need in large amounts for energy and growth. Now, we are moving on to micronutrients (vitamins and minerals) and water.

Even though we only need vitamins and minerals in tiny amounts, they are like the "spark plugs" of an engine—without them, our bodies cannot function properly. Let’s dive in and see how these nutrients keep us healthy and what happens if we don't get enough of them!

1. Fat-Soluble Vitamins (A, D, E, and K)

These vitamins are called "fat-soluble" because they dissolve in fats and oils. Our bodies can store them in the liver and fatty tissues for a long time. This means we don't necessarily need to eat them every single day, but we must be careful not to have too much (over-nutrition).

Vitamin A

  • Properties: Destroyed by high heat and prolonged exposure to air.
  • Functions: Essential for night vision, healthy skin, and maintaining the lining of the breathing and digestive tracts.
  • Sources: Retinol (from animal sources like liver, eggs, milk) and Beta-carotene (from yellow/orange vegetables like carrots and dark green leafy vegetables).
  • Deficiency:
    • Short-term: Night blindness (difficulty seeing in dim light).
    • Long-term: Total blindness and dry, scaly skin.

Vitamin D

  • Properties: Stable to heat and cooking.
  • Functions: Helps the body absorb calcium and phosphorus to build strong bones and teeth.
  • Sources: Sunlight (the body makes it through the skin), oily fish, and fortified margarine.
  • Deficiency:
    • In children: Rickets (soft, deformed bones like "bow-legs").
    • In adults: Osteomalacia (weak, painful bones that break easily).

Vitamin E

  • Functions: Acts as an antioxidant to protect body cells from damage and maintains healthy skin and eyes.
  • Sources: Vegetable oils, nuts, seeds, and wheat germ.
  • Deficiency: Very rare, but can lead to nerve and muscle damage.

Vitamin K

  • Functions: Essential for normal blood clotting (helping wounds heal so you don't bleed too much).
  • Sources: Green leafy vegetables and made by bacteria in our gut.
  • Deficiency: Excessive bleeding and slow wound healing.

Quick Review: Remember A, D, E, K. A simple way to remember them is: "All Dogs Eat Kibble." These are the ones stored in fat!

2. Water-Soluble Vitamins (B Complex and Vitamin C)

These vitamins dissolve in water and cannot be stored in the body for long. Any extra is flushed out in urine. Therefore, we need to eat foods containing these vitamins every day.

Vitamin B Complex

The B group vitamins usually work together to help the body release energy from food.

  • Thiamin (Vit. B1): Needed for energy release from carbohydrates. Deficiency: Beri-beri (weakness and nerve problems).
  • Riboflavin (Vit. B2): Needed for energy release and healthy skin. Deficiency: Sores at the corners of the mouth.
  • Niacin: Helps with metabolism and the nervous system. Deficiency: Pellagra (diarrhoea, dermatitis, dementia).
  • Vitamin B6: Involved in protein metabolism and red blood cell formation.
  • Folate: Essential for DNA synthesis and preventing neural tube defects in unborn babies. Deficiency: Anaemia.
  • Vitamin B12: Works with folate to make red blood cells and maintains the nervous system. Deficiency: Pernicious anaemia.

Vitamin C (Ascorbic Acid)

  • Properties: Very unstable! It is easily destroyed by heat, air, and dissolves into cooking water.
  • Functions: Helps with iron absorption, wound healing, and building collagen (connective tissue).
  • Sources: Citrus fruits (oranges, lemons), kiwi, and broccoli.
  • Deficiency:
    • Short-term: Swollen, bleeding gums and slow wound healing.
    • Long-term: Scurvy (severe weakness and loss of teeth).

3. Minerals: Calcium, Phosphorus, and Iron

Minerals are inorganic elements that help regulate body processes and build tissues.

Calcium and Phosphorus

These two minerals work together like "partners" to build our skeletal structure.

  • Functions: Building and maintaining bones and teeth. Calcium is also needed for blood clotting and muscle function.
  • Sources: Dairy products (milk, cheese), small fish with bones (sardines), and tofu.
  • Deficiency: Rickets in children and Osteoporosis (brittle bones) in older adults.

Iron

  • Functions: Forms haemoglobin in red blood cells, which carries oxygen around the body.
  • Sources: Red meat, liver, spinach, and fortified cereals.
  • Deficiency: Anaemia. Symptoms include feeling very tired, pale skin, and shortness of breath.

4. Nutrient Interrelationships (Crucial for Exams!)

In the HKDSE, you are often asked how nutrients affect each other. Some nutrients help each other (synergy), while others block each other (antagonism).

The "Good" Partnerships (Helpers):

  • Iron and Vitamin C: Vitamin C changes iron into a form that is easier for the body to absorb. (Example: Drinking orange juice with a steak.)
  • Calcium and Vitamin D: Vitamin D is required for the body to absorb calcium effectively. Without Vit D, your bones won't get the calcium they need.
  • Calcium and Phosphorus: These must be present in the correct ratio to form strong bone tissue.

The "Bad" Partnerships (Blockers):

  • Iron and Dietary Fibre: High amounts of fibre (phytates) can bind with iron and prevent it from being absorbed.
  • Calcium and Dietary Fibre: Similar to iron, too much fibre can interfere with calcium absorption.

5. Water

Water is the most important nutrient—you can survive for weeks without food, but only a few days without water!

Functions of Water

  • Transportation: Carries nutrients to cells and carries waste products away (in urine).
  • Temperature Regulation: Cools the body through sweating.
  • Lubrication: Keeps joints and eyes lubricated.
  • Chemical Reactions: Needed for digestion and metabolism.

Sources and Intake

  • Sources: Drinks (water, tea, milk) and solid foods (fruits like watermelon and vegetables like cucumber are mostly water).
  • Recommended Intake: Generally 6 to 8 glasses a day, but more is needed in hot weather or during heavy exercise.

Summary Checklist

  • Fat-soluble: A, D, E, K (Stored in the body).
  • Water-soluble: B complex and C (Need daily, destroyed by heat).
  • Iron: Needs Vitamin C for absorption; prevents anaemia.
  • Calcium: Needs Vitamin D for absorption; prevents osteoporosis.
  • Water: Essential for transport and temperature control.

Exam Tip: If a question asks why a vegetarian might feel tired, don't just say "lack of iron." Mention that they might not be getting enough Vitamin C to help absorb the iron from their vegetables, or they might be eating too much fibre that blocks iron absorption!