Diet

Quick revise

All organisms require food to survive. It provides energy and the raw materials for growth. We take our food in ready-made as complicated organic molecules.  These food molecules can be placed into seven main groups. A balanced diet needs the correct amounts of each of these types of food molecules.

A Balanced Diet

A balanced diet is the correct amount of each food, not simply ‘enough’ food

Carbohydrates -  starch and sugars,supply Glucose or store of energy

  • Simple carbs -Found in sweets, jam, cakes. You shouldn’t eat too much of these.
  • Complex carbs - Found in bread, pasta, rice, potatoes, cereal. These should make up the main part of your meal.

Fats  - fatty acids and glycerol rich store of energy. Provide energy and keeps us warm.

  • Saturated fats - Found mainly in animal products
  • Monosaturated fats -Found in many foods, like olive oil
  • Polyunsaturated fats - Found in some margarines and oils, and oily fish

Proteins - long chains of amino acids growth and repair

  • Helps body grow and repair itself.
  • Found in foods such as meat, fish, eggs, milk and soya beans

Minerals  -different elements. Builds healthy bones and teeth and help in various chemical reactions e.g.

  • Calcium –needed for strong bones and teeth, and muscle contraction. Found in green veg, milk, cheese and some fish.
  • Iron – handy for haemoglobin in red blood cells. Found in liver, beans and green veg
  • Iodine – needed for thyroid hormones. Found in sea food.

Vitamins  - Help bones, skin and teeth grow. Needed for the body’s chemical reactions.

  • Fat-Soluble Vitamins - Can be stored in the body
    • Vitamin A –useful for night vision and growth. Found in vegetables, eggs and liver.
    • Vitamin D –strengthens bones. Made by the skin in sunshine, and found in milk, fish, liver and eggs.
  • Water-Soluble Vitamins - Can’t store, so need to be eaten regularly.
    •  Vitamin C –good for skin, connective tissue and gums. Found in fruit and veg, particularly citrus fruits. Prevents scurvy

Fibre -Needed to keep your digestive system working properly

  • Lots of fibre in fruit and veg
  • cellulose prevents constipation

Water - all chemical reactions take place in water

  • Water is needed in lots of chemical reactions in the body. It’s lost in your breath, sweat, urine and faeces.
  • If you don’t drink enough to replace what your body uses or loses, you will suffer from dehydration, and won’t perform as well.
  • If you drink too much, your kidneys will produce more urine to get rid of the excess.

The exact amount of each substance that is needed in a balanced diet will vary.  It depends on

  • how old the person is,
  • whether they are male or female
  • how active they are.

For example, teenagers need a high-protein diet to provide the raw materials for growth. You can estimate the recommended daily average (RDA) protein intake for a person using the formula:

  • RDA in g = 0.75 × body mass in kg
  • There are differences between the sexes because of the time of the growth spurt and due to periods in girls.

The amount and type of protein is important. Proteins from animals are called first class proteins because they contain more variety of amino acids compared with plant proteins. Some people’s diet may be influenced by other factors than just their daily requirements. Some people may be vegetarians or vegans and some religions require certain diets to be followed. Some people may have to avoid certain foods to prevent them becoming ill.

Correct Food for Exercise

Different sports place different demands on the body, so athletes need to eat specific foods.

  • Weightlifters / sprinters need muscle power, so need lots of protein for muscle growth
  • Gymnasts need to be strong, but also light, so need a good balance of carbs, proteins and fat
  • Marathon runners need endurance, so need lots of carbs for energy

This video looks at a balanced diet for a sportman

Eating around Exercise / Activity

Different sports place different demands on the body, so athletes need to eat specific foods.

  • Weightlifters / sprinters need muscle power, so need lots of protein for muscle growth
  • Gymnasts need to be strong, but also light, so need a good balance of carbs, proteins and fat
  • Marathon runners need endurance, so need lots of carbs for energy

 

Register for Free

Get full free access to thousands of GCSE and A-Level revision resources.

Create a revision timetable to organise your study time.

Sign Up Now