Vitamins - A general guide to vitamins A, B, C, D, E and K.
Vitamins are derived from food and are essential to keep the body healthy and the mind alert. Although they do not provide energy or make up our cells or organs, without them the body cannot carry out many of the chemical processes it needs.
A lack of certain vitamins can lead to fatigue, poor skin, teeth and bones and in some cases of severe deficiency, it can lead to serious illness.
Vitamins interact with other nutrients in processes such as metabolism, digestion and developing blood cells and some vitamins are said to slow down the ageing process, prevent cancerous cells attacking the body and strengthen the immune system.
There are 13 different vitamins that can be divided into two categories: water-soluble and fat-soluble.
Vitamins A, D, E and K are fat-soluble vitamins. Fat-soluble vitamins are absorbed from dietary fats in the intestine and are then stored in the liver until needed. This means that they do not have to be consumed every day.
Water-soluble vitamins on the other hand, need to be consumed from foods every day, as any excess vitamins are lost through urine and cannot be stored in the body.
Water-soluble vitamins play an important part in the break down, metabolism and digestion of protein, fats and carbohydrates and the subsequent release of energy into the body and without an adequate supply of these vitamins, these processes may not be properly completed.
Many vitamins are found in fruit and vegetables. Ideally, these food sources should be eaten raw, as vitamins can be lost or partially lost through the cooking process.
However, just as the right amount of vitamins is essential for good health, the intake of too many vitamins can also be harmful.
Below is a guide to each vitamin, which includes in which foods they can be found, their function in the body and how the body is affected by a deficiency of that vitamin.
Vitamin A (Retinol)
Function: Important for healthy bones, teeth, mucous membranes and skin. Aids vision, especially in the dark. Carotenoids, which are other forms of vitamin A are powerful antioxidants.
Sources: Retinol - meat, eggs, oily fish, liver, milk, cheese, kidney.
Carotenoids - carrots, sweet potatoes, apricots, cantaloupe melon, broccoli, spinach, pumpkin and all other green and orange fruits and vegetables.
Symptoms of deficiency: Poor night vision, eye problems, weakened immune system and more prone to infection.
Vitamin B1 (Thiamin)
Function: Protects the heart and the nervous system from the build-up of toxic substances and is needed to convert carbohydrates and fats into energy.
Sources: lean meats particularly pork, fortified bread and cereals, whole grains, dried beans, potatoes, spinach, nuts, peas, yeast.
Symptoms of deficiency: Tiredness and fatigue, muscle weakness, nerve damage, confusion, enlarged heart. More common in alcoholics.
Vitamin B2 (Riboflavin)
Function: Vital for growth, the production of red blood cells and releasing energy from food.
Sources: poultry, lean meat, eggs, milk, fish, yoghurt, yeast, soy beans, legumes, almonds, leafy green vegetables and fortified breads and cereals.
Symptoms of deficiency: Skin disorders, dry and cracked lips, bloodshot eyes and sore throat, although B2 deficiency is not common in the developed world.
Vitamin B3 (Niacin)
Function: Maintains a healthy skin and keeps the digestive system working well.
Sources: poultry, lean meat, peanuts, pulses, potatoes, milk, eggs, liver, heart, kidney, fortified breakfast cereals, broccoli, carrots, avocados, tomatoes, dates, sweet potatoes, whole grains, mushrooms.
Symptoms of deficiency: Skin disorders, fatigue, depression and diarrhoea.
Vitamin B5 (Pantothenic acid)
Function: It is needed for the metabolism and synthesis of all foods.
Sources: eggs, meat, liver, dried fruit, fish, whole grain cereals, pulses. B5 is found in all foods in small quantities.
Symptoms of deficiency: A deficiency in this case is extremely rare, however, symptoms may include tiredness and a loss of feeling in the toes.
Vitamin B6 (Pyridoxine)
Function: Required for the formation of red blood cells and various neurotransmitters and helps to maintain nerve function, a healthy immune system and healthy antibodies.
Sources: lean meat, eggs, chicken, liver, fish, beans, nuts, whole grains and cereals, bananas and avocados.
Symptoms of deficiency: skin disorders, mouth sores, confusion, depression and anaemia.
Vitamin B7 (Biotin)
Function: Essential in the metabolism and synthesis of essential fatty acids, carbohydrates and fats and the release of energy from these foods. Keeps hair, skin and nails healthy.
Sources: Biotin is found in almost all types of food. High amounts are present in liver, butter, yeast extracts, eggs, dairy produce and fortified cereals.
Symptoms of deficiency: Deficiency of biotin is rare but can occur if large amounts of raw egg whites are consumed. Symptoms include hair loss or brittle hair, skin rashes and fungal infection. This could lead to depression and muscular pain.
Vitamin B9 (Folic acid)
Function: Required for the production of red blood cells, DNA and proteins in the body. It is important for the growth and repair of cells and tissues and is especially important during pregnancy to prevent babies being born with spina bifida.
Sources: leafy green vegetables, citrus fruits, pulses, wheatgerm, fortified cereals, liver, pork, poultry, broccoli, yeast.
Symptoms of deficiency: anaemia, incorrect absorption of essential nutrients and neural tube defects in babies.
Function: Required for the metabolism process and to maintain the nervous system.
Sources: Eggs, shellfish, poultry, meat, dairy produce, liver, fortified cereals.
Symptoms of deficiency: Tiredness and fatigue, tingling and numbness in the hands and feet, loss of memory, anaemia and confusion.
Vitamin C (Ascorbic acid)
Function: Vitamin C is required daily and is necessary for a number of functions in the body. It is required for the formation of collagen, which helps to maintain skin, teeth, gums, tendons and ligaments.
Vitamin C aids to heal wounds quicker, strengthen the immune system and fight cancerous cells. It is required to form neurotransmitters such as dopamine in the brain and helps to reduce any damage to the body from toxic substances and chemicals.
Sources: Citrus fruits, melon, strawberries, blackcurrants, green peppers, tomatoes, broccoli, kiwi fruit, potatoes, dark green leafy vegetables, red peppers, squash, mango, papaya, cauliflower, pineapple, blueberries, raspberries and cranberries.
Symptoms of deficiency: Prone to infections, slower healing of wounds, dental and gum problems, fatigue, loss of appetite, dry skin, painful joints, anaemia and a slower metabolism.
Vitamin D is needed to absorb calcium and strengthen bones and teeth and can prevent the onset of osteoporosis. It is also known as the "sunshine" vitamin, as 15 minutes of exposure to the sunshine, three times a week will enable the body to manufacture all the vitamin D that it needs.
dairy produce, oily fish and fish oils, eggs, oysters
and fortified cereals.
Symptoms of deficiency:
Softening and weakening of the bones, insomnia, nervousness and muscle weakness.
Vitamin E (Tocopherol)
Function: Vitamin E is an important antioxidant that protects the cells and tissue from harmful substances and free radicals. As well as preventing cancer, it is also known to prevent cardiovascular and heart disease. Vitamin E is often added to skin creams, due to claims that it may delay the ageing process.
Sources: vegetable oils such as canola, palm, sunflower, olive and soybean. Also found in nuts, seeds, wheat germ, spinach, green leafy vegetables, asparagus and cereals.
Symptoms of deficiency: Deficiencies are not very common but may include some nerve damage.
Function: Essential for blood clotting, which is important if large amounts of blood is lost. It also helps to maintain strong bones and could prevent osteoporosis.
Sources: spinach, cauliflower, kale, green leafy vegetables, soya beans, spring onions and pistachio nuts.
Symptoms of deficiency: Deficiency is rare, as vitamin K is manufactured in the body. Signs of deficiency include easy bruising and bleeding.