Balanced Diet (Edexcel IGCSE Biology: Double Science)

• A balanced diet consists of all of the food groups in the correct proportions
• The necessary key food groups are:
  • Carbohydrates
  • Proteins
  • Lipids
  • Dietary fibre
  • Vitamins
  • Minerals (mineral ions)
  • Water

Malnutrition

• Having an unbalanced diet can lead to malnutrition
• Malnutrition can cause a variety of different health problems in humans

Causes and effects of malnutrition table

• There are seven main food groups. These are:
  • Carbohydrates
    • Function: source of energy
    • Sources: bread, cereals, pasta, rice, potatoes
  • Protein
    • Function: growth and repair
    • Sources: meat, fish, eggs, pulses, nuts
  • Lipid (fats and oils)
    • Function: insulation and energy storage
    • Sources: butter, oil, nuts
  • Dietary fibre
    • Function: provides bulk (roughage) for the intestine to push food through it
    • Sources: vegetables, whole grains
  • Vitamins and minerals
    • Function: needed in small quantities to maintain health
    • Sources: fruits and vegetables, meats, dairy products
  • Water
    • Function: needed for chemical reactions to take place in the body
    • Sources: water, juice, milk, fruits and vegetables

• Some examples of vitamins and minerals include: 
  • Calcium is needed for strong teeth and bones and is involved in the clotting of blood
    • A deficiency can lead to osteoporosis later in life
    • It is found in milk, cheese, and eggs
  • Vitamin D helps the body to absorb calcium and is required for strong bones and teeth
    • It can be found in oily fish and dairy products, and is also made naturally by the body in sunlight
  • Vitamin C forms an essential part of collagen protein, which makes up the skin, hair, gums, and bones
    • A deficiency can cause scurvy. It is found in citrus fruits and some green vegetables
  • Vitamin A is needed to make the pigment in the retina for vision
    • It can be found in meat, liver, dairy, leafy green vegetables like spinach, and eggs
  • Iron is needed to make haemoglobin, the pigment in red blood cells that helps to carry oxygen
    • It can be found in red meat, liver, leafy green vegetables, and spinach

Sources and uses of vitamins and minerals in the human body diagram

Vitamins and minerals are necessary for a range of functions inside the human body

• The nutritional requirements for individuals will vary throughout their lifetime
• An individual will still require the same key food groups, but in different quantities depending on a number of factors such as age, height, sex, activity levels, pregnancy and breastfeeding
  • The amount of energy that young people need increases towards adulthood as this energy is needed for growth Children need a higher proportion of protein in their diet than adults as this is required for growth
    • Energy needs of adults decrease as they age
  • The more active, the more energy required for movement as muscles are contracting more and respiring faster
  • During pregnancy, energy requirements increase as energy is needed to support the growth of the developing fetus, as well as the larger mass that the mother needs to carry around. Extra calcium and iron are also needed in the diet to help build the bones, teeth, and blood of the fetus
  • For breastfeeding mothers, energy requirements increase and extra calcium is still needed to make high-quality breast milk
  • Male average energy requirements tend to exceed that of females due to them having a larger proportion of muscle compared to fat