Fat Soluble Vitamins Definition and Examples

What are Fat-Soluble Vitamins? 

There are four vitamins in this group. They are vitamins A, D, E, and K. They dissolve in fat.

This article tells you:

  • the chemical names of each fat-soluble vitamin
  • why the body needs these vitamins
  • the foods which give us these vitamins
  • what happens if we do not have enough (a deficiency) of these vitamins • what happens to these vitamins when foods are processed and cooked.

Vitamin A (Retinol in animal food sources or beta carotene in plant food sources)

Function (its job in the body):

  • It helps the body grow and develop
  • It keeps the lining of the throat, the digestive system and the lungs moist and free from infection
  • It keeps the skin healthy
  • It makes a substance called visual purple, in the retina at the back of the eye so we can see well enough in dim light to stop us bumping into things
  • It is an antioxidant so it helps stop substances that get into the body from the air, water and elsewhere from damaging it.

Vitamin A is found in foods in two different forms:

  • as retinol in animal foods, e.g. milk, cheese, butter, oily fish (e.g. tuna, herrings, mackerel, sardines), liver and liver products e.g. pate
  • as beta carotene in plant foods, e.g. carrots, oranges, red peppers, saffron, dark green leafy vegetables, tomatoes, palm fruit, apricots, margarine (added by law, a process called fortification)

Beta carotene is changed to retinol in the body.

Deficiency (what happens if we do not have enough):

  • Children do not grow properly
  • It becomes difficult for the body to fight infection
  • The person will not be able to see in dim light – this is called night blindness
  • This will eventually lead to blindness – a condition known as keratomalacia (very common in poor countries)
  • Too much vitamin A is poisonous to the body. People should be careful when they take vitamin supplements and should only do so on the advice of their doctor. Vitamin A is not affected by most cooking processes.

Vitamin D (Cholecalciferol)

Function (its job in the body):

  • Vitamin D controls the amount of calcium that is absorbed from food in the body
  • It also helps us to develop strong bones and teeth by making sure that they take up plenty of minerals such as calcium and phosphorus. It is important that the bones reach their ‘peak bone mass’ during childhood, adolescence and early adulthood so that they are their strongest and will last a long time without becoming weak.

Sources (the food it is found in):

  • A few foods contain some vitamin D – liver, oily fish, butter, cheese, milk and eggs and it is added by law to margarine
  • Most of our vitamin D comes from exposure of the skin to sunlight. When the rays of the sun reach the skin, a chemical reaction takes place under the skin to form vitamin D, which is then stored in the liver.

Deficiency (what happens if we do not have enough):

  • A deficiency of vitamin D means that not enough calcium is absorbed from food, and the bones and teeth do not become strong enough
  • The weak bones bend under the weight of the body and become deformed. In children this disease is called rickets and if it happens in adults it is called osteomalacia (means ‘bad’ bones)
  • Osteomalacia is not the same as osteoporosis, which is a natural process where the bones become weaker as people get older.

Vitamin D is not affected by normal cooking processes.

Vitamin E (Tocopherol)

Function (its job in the body):

  • Vitamin E is an antioxidant so it helps stop substances that get into the body. from the air, water and elsewhere from damaging it
  • It is needed to make sure that the cell walls in the body stay healthy
  • It is thought to reduce the risk of people developing some types of cancers and heart disease.

Sources (the food it is found in):

  • vegetable oils
  • lettuce
  • grasses
  • peanuts
  • seeds
  • wheatgerm oil

A deficiency of vitamin E is rare.

Vitamin E is not affected by normal cooking processes.

Vitamin K

Function (its job in the body):

Vitamin K helps the blood to clot. This means that when we bleed following an injury, the blood will thicken and ‘clot’ at the place where the injury took place in order to allow it to be repaired and to stop us from losing too much blood.

Sources (the food it is found in):

  • Vitamin K is found in plant and animal foods especially leafy vegetables, cheese, liver, asparagus, coffee, bacon and green tea
  • It is also made by bacteria that live naturally in our intestines.

Deficiency (what happens if we do not have enough):

  • Deficiency is very rare in adults, but is sometimes seen in newborn babies
  • To prevent this, a dose of vitamin K is normally given to babies straight after birth, either by mouth or an injection.

Vitamin K is not affected by normal cooking processes.

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