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What are vitamins?

The term 'vitamin' is derived from 'vital amine'. They are a group of substances required in small amounts for growth and development but which cannot be manufactured by the body.

Without vitamins the human body would not survive. We all need vitamins in order to live a long and healthy life. Most of us get sufficient quantities of vitamins from our food, but it may be necessary for some people to take a vitamin supplement (eg pregnant women and the elderly).

How easy is it to get all the vitamins we need from our diet?

A varied diet is essential if we are to obtain the nutrients we need. However, this is not always easy: fruit and vegetables age (an apple in a bowl loses vitamins hour by hour) and deep frozen products may often contain more vitamins than vegetables stored for a long time at room temperature. Therefore, it is especially important to eat a wide variety of fresh foods.

Too little of just one vitamin may disturb the body's balance and cause health problems. But taking too many vitamins can also be dangerous. This is especially true of the fat-soluble vitamins A, D, E and K: it is harder to get rid of excess of these vitamins through urine - the most common way for us to eliminate body waste products.

Which vitamins do we know about?

New vitamins are discovered occasionally, but presently we know of the following vitamins: A, B1, B2, B3, B5, B6, B10, B11, B12, B13, B15, B17, C, D, E, F, G, H, K, L, M, P, T and U.

Where do vitamin supplements come from?

Most vitamin supplements have been extracted from natural foods. For instance, vitamin A comes from fish-liver oil. Vitamin B comes from yeast or liver. Vitamin C is often extracted from small berries in roses, and vitamin E is extracted from soy beans or maize. Vitamins may also be synthetically manufactured, but synthetic vitamins are not always as effective as their naturally-derived equivalent.

How should vitamins be stored?

It is important to keep vitamins in a dark, cool place, or they will 'go off', just like apples in a bowl. The best place to store vitamins is in the refrigerator - make sure there is a lid on the container. A few grains of rice in the container will prevent moisture getting into the tablets.

When should you take vitamin supplements?

The best time to take vitamins is during the day, after a meal. Never take vitamins on an empty stomach - they will quickly passed out in your urine. This is especially true for the B and C vitamins that dissolve in water. The fat-soluble vitamins A, D, E and K can be stored in the body for up to 24 hours and can sometimes be stored in the liver for even longer.

Are vitamins and minerals the same thing?

Vitamins and minerals are two completely different things: minerals help the vitamins work. The 10 most important minerals are: calcium, iodine, iron, magnesium, phosphorus, copper, manganese, chromium, selenium and zinc. There is a specific recommended daily allowance for each of these, as well as for each of the vitamins.

Recommended daily amounts (RDAs)

Throughout this factsheet, recommended daily amount refers to the European Union recommended daily amounts (EU/RDA) for nutritional labelling of food products. Nutritional requirements are often slightly different for young children and adolescents, and during pregnancy and breastfeeding. Ask your doctor or pharmacist if you are concerned about your own or your children's vitamin intake.

Vitamin A (retinol) properties

Good for:

• eyesight
• growth
• appetite and taste.

Signs of vitamin A deficiency:

• night-blindness.

Good sources of vitamin A:

• liver
• fish-liver oil
• carrots
• green leafy vegetables
• egg yolks
• enriched margarine
• milk products
• yellow fruits.

Recommended daily amount: 800 micrograms.

Poisoning: vitamin A is a fat-soluble vitamin and so it is stored for a long time in the human body, especially in pregnancy. An overdose may be dangerous.

Destroyed by: fatty acids.

Vitamin B1 (thiamine) properties

Good for:

• nervous system
• digestion
• muscles
• the heart
• alcohol-damaged nervous tissues.

Signs of vitamin B1 deficiency:

• tingling in fingers and toes
• confusion
• difficulties in maintaining balance
• loss of appetite
• exhaustion
• weakened powers of concentration.

Good sources of vitamin B1:

• liver
• yeast
• rice
• wholemeal products
• peanuts
• pork
• milk.

Recommended daily amount: 1.4mg.

Poisoning: no poisoning dangers as the vitamin dissolves in water, so excess is excreted in the urine.

Destroyed by: high temperatures, alcohol and coffee.

Vitamin B2 (riboflavin) properties

Good for:

• growth
• skin
• nails
• hair
• sensitive lips and tongue
• eyesight
• protein, fat and carbohydrate breakdown.

Signs of vitamin B2 deficiency:

• itching and irritation of the eyes
• itching mucous membranes
• itching lips and skin.

Good sources of vitamin B2:

• milk
• liver
• yeast
• cheese
• green leafy vegetables
• fish.

Recommended daily amount: 1.6mg.

Poisoning: no danger of poisoning as the vitamin dissolves in water, so excess is excreted in the urine.

Destroyed by: light (this is why milk-cartons are better than bottles) and alcohol.

Vitamin B6 (pyridoxine) properties

Good for:

• preventing skin conditions
• nerve problems
• helping the body absorb proteins and carbohydrates.

Signs of vitamin B6 deficiency: skin inflammation.

Good sources of vitamin B6:

• fish
• bananas
• chicken
• pork
• whole grains
• dried beans.

Recommended daily amount: 2mg. Women taking the contraceptive pill may need more.

Poisoning: may cause nerve problems in large doses, but current evidence is conflicting about the maximum safe dose. Discuss this with your pharmacist if you are concerned.

Destroyed by: the contraceptive pill, roasted or boiled food, alcohol and oestrogen (the female hormone).

Vitamin B12 (cobalamin) properties

Good for:

• making red blood cells
• the formation of the nerves.

Signs of vitamin B12 deficiency:

• tiredness due to anaemia
• abnormalities of nervous tissue function.

Good sources of vitamin B12:

• fish
• liver
• beef
• pork
• milk
• cheese.

Vitamin B12 deficiency can arise in strict vegans because our dietary sources of vitamin B12 are animal in origin. The other main cause of vitamin B12 deficiency is pernicious anaemia.

Recommended daily amount: 1 microgram.

Poisoning: no danger as the vitamin dissolves in water, so excess is excreted in the urine.

Destroyed by: water, sunlight, alcohol, oestrogen and sleeping pills.

Vitamin C (ascorbic acid) properties

Good for:

• the immune defence system
• protection from viruses and bacteria
• healing wounds
• reducing cholesterol content of the blood
• a natural laxative
• cell lifespan
• preventing scurvy.

Signs of vitamin C deficiency:

• tiredness
• bleeding gums
• slow-healing wounds.

Good sources of vitamin C:

• citrus fruits - especially kiwi fruit
• berries
• tomatoes
• cauliflower
• potatoes
• green leafy vegetables
• peppers.

Recommended daily amount: 60mg.

Poisoning: Large doses can cause diarrhoea and nausea. Some scientists have recently argued that 1 to 5g per day may influence your genes.

Destroyed by: boiling food, light, smoking and heat.

Vitamin D properties

Good for:

• strong bones and teeth.

Signs of vitamin D deficiency:

• unhealthy teeth
• osteomalacia (causes weakening of bones)
• rickets in children.

Good sources of vitamin D:

• cod-liver oil
• sardines
• herring
• salmon
• tuna
• milk and milk products
• sunlight (the action of sunlight on the skin allows our bodies to manufacture vitamin D).

Recommended daily amount: 5 micrograms.

Poisoning: this vitamin is fat-soluble so can accumulate in the body and overdoses are dangerous.

Destroyed by: mineral oil.

Vitamin E (tocopherol) properties

Good for:

• fighting poisons - vitamin E is a powerful 'anti-oxidant'.

Signs of vitamin E deficiency:

• weak muscles
• fertility problems.

Good sources of vitamin E:

• nuts
• soya beans
• vegetable oil
• broccoli
• sprouts
• spinach
• wholemeal products
• eggs.

Recommended daily dose: 10mg

Poisoning: there is a theoretical but slight risk of overdose, as vitamin E is fat soluble.

Destroyed by: heat, oxygen, frost, iron, chlorine and mineral oil.

Folic acid properties

Good for:

• production of red blood cells
• essential during the first three months of pregnancy to prevent birth defects such as spina bifida, cleft palate or cleft lip.

Signs of folic acid deficiency: anaemia, red tongue.

Good sources of folic acid:

• carrots
• yeast
• liver
• egg yolks
• melon
• apricots
• pumpkin
• avocado
• beans
• rye and whole wheat
• green leafy vegetables.

Recommended daily amount: 200 micrograms. Pregnant women and women planning a pregnancy should take a daily supplement of 400 micrograms, continued for the first 12 weeks of pregnancy.

Poisoning: no danger of poisoning as it dissolves in water, so excess is excreted in the urine.

Destroyed by: water, sunlight, oestrogen, heat.

Vitamins and minerals play an important role in a number of the body's metabolic pathways and are essential for the maintenance of good health and the prevention of a number of diseases.

Vitamins and minerals

There are two types of vitamins:

• water-soluble - vitamins C and B
• fat-soluble - vitamins A, D, E and K.

Water-soluble vitamins cannot be stored in the body and can be destroyed by overcooking.

Vitamins and minerals are found in a wide variety of foods and a balanced diet should provide you with the quantities you need. However, modern food processing has considerably reduced the vitamin and mineral content of many foods.

Vitamin A

This vitamin is essential for growth, healthy skin and hair, and is also a powerful antioxidant that plays a key role in the body's immune system. Vitamin A, also known as retinol, is found in the following animal products:

• butter
• cheese
• chicken
• eggs
• fish oils
• herring
• kidney
• liver
• liver pate
• mackerel
• milk
• trout.

Another source of vitamin A is a substance found in orange, yellow and green vegetables and fruits called beta-carotene. This is converted by the body into vitamin A and is also a powerful antioxidant. An adult needs about 600-700 micrograms of vitamin A daily.

Folic acid

Folic acid (folate) is an important compound that works closely in the body with vitamin B12, where it is involved with the metabolism of amino acids and the synthesis of proteins. Most importantly, it is needed for both the repair and production of RNA and DNA, making it vital to healthy cell replication. Folate is also linked to the production of healthy blood cells and deficiency of folate is one of the main causes of anaemia, particularly in people whose diet is generally poor.

Insufficient folate levels are associated with an increased risk of incomplete development of the spinal cord system (spina bifida) in a growing foetus and all pregnant women are now advised to take folate supplements in early pregnancy, and preferably before conception.

Folate occurs naturally in most foods but mainly in small amounts. Many food manufacturers now fortify white flour, cereals, bread, corn, rice and noodle products with folic acid. A serving of each enriched product will contribute about 10 per cent of the daily value for folic acid. Whole grain products are not enriched as they already contain natural folate.

Liver has the greatest concentration of folate, with lower levels found in beef, lamb and pork and a range of green vegetables and citrus fruits. The major sources of folate are found in the following foods:

• asparagus
• avocados
• beef
• broccoli
• citrus fruits
• collards
• curly kale
• dried beans
• dried peas
• lamb
• liver
• orange juice - fresh
• pork
• savoy cabbage
• spinach
• tomatoes
• turnip
• wheat germ (wholemeal bread and cereal)
• wholegrain products (pasta and brown rice).

If you need to increase or modify your intake of folate, the following practical tips will assist you in achieving your goals:

• eat folate-rich food as soon after purchase as possible.
• keep cooking time to a minimum.
• whenever possible lightly steam your vegetables.
• if you have been advised to take a folic acid supplement, follow the recommended dosage . In pregnancy a supplement of 400 micrograms per day is advised until at least the 12th week.

Adults are recommended to consume 200-500 micrograms of folate per day.

Table 1: Indication of the folate content of foods

Vitamin B Complex

The complex of B vitamins includes the following group of substances:

• B1 - thiamine
• B2 - riboflavin
• B3 - nicotinic acid
• B6 - pyridoxine
• B12 - cobalamin
• folate - folic acid.

These vitamins are available in a wide variety of foods and the body requires relatively small amounts of vitamins B1, B2 and B3.

Vitamins B12 and B6 play an important role in the body's metabolism of folic acid and are vital nutrients in a range of activities including cellular repair, digestion, the immune system and the production of energy.

Vitamin B12 is needed for fat and carbohydrate metabolism and is involved in folic acid metabolism. As a result, deficiency of either vitamin results in similar signs and symptoms, and anaemia will result. The correction of folic acid deficiency is done by giving folate supplements but in addition vitamin B12 and B6 are also given. This is because there may be unsuspected B12 deficiency along with the lack of folate, and the sudden availability of folate may use up the remaining B12, which is known to potentially be harmful to the nerves of the spinal cord.

The best dietary sources of the B vitamins, especially B12, are found in animal products and yeast extracts. Other sources include:

• asparagus
• bananas
• broccoli
• brown rice
• cheese
• dried apricots
• dried dates and figs
• eggs
• fish
• milk
• nuts
• potatoes
• poultry
• pulses
• red meat
• spinach
• wheat germ
• wholegrain cereals
• yeast extract (eg marmite)
• yoghurt.

Vegetarians who consume eggs and dairy produce will obtain sufficient B12, however, if neither is consumed attention must be paid to B12 intake, and if necessary it should be supplemented.

The British Vegan Society recommends the following sources of vitamin B12:

• yeast extracts (eg Marmite)
• margarine
• soya powder
• Plamil
• soya milk
• breakfast cereals
• Unisoy Gold Soya milk
• soya mince or chunks.

Vitamin B6 is one of the most essential and widely utilised enzymes in the body and is involved in roughly 100 enzymatic reactions including 60 involving amino acids, the building blocks of protein and essential fatty acids.

Deficiency has been found to bring about a wide variety of symptoms, the most common of which involve the skin and nervous system. Vitamin B6 plays an essential role in folate metabolism and supplementing folic acid without paying attention to vitamin B6 Llvels will not be effective.

A mild deficiency of vitamin B6 may cause problems such as dermatitis, sore tongue and sore cracks at the corner of the mouth.

The best sources of vitamin B6 are similar to those for Vitamin B12 and include the following foods:

• avocado
• brewers yeast
• eggs
• herring
• kidney
• liver
• pork
• poultry
• salmon
• sunflower seeds
• walnuts
• wheat germ.

To improve your diet's content of B vitamins follow these practical tips:

• try not to drink large quantities of tea, coffee or cola-based drinks as caffeine inhibits the absorption and increases the excretion of vitamins.
• alcohol is toxic towards these vitamins so moderate or remove alcohol from your diet.
• vitamins are affected by cooking so it's best to steam or poach your food to reduce the loss of nutrients.
• try to ensure that food is fresh and consumed as soon as possible.

Vitamin C

Also known as ascorbic acid, vitamin C is one of the most potent antioxidant vitamins. It is needed for healthy body tissue, is vital for growth, for wound repair and an efficient immune system. Fresh fruits and vegetables are the main source of vitamin C and absence of adequate dietary intake gives rise to scurvy, the scourge of long sea-voyages in centuries gone by but still a significant nutritional problem in many developing countries. In addition, it is linked to lowering of cholesterol levels, regulating blood pressure and the absorption of iron.

Vitamin C is a water-soluble vitamin and the body cannot store amounts in excess of its needs - the recommended daily intake is 60mg. People with higher than average requirements include smokers but surplus vitamin C in the diet is excreted in the urine. Too much vitamin C can result in sensitive and irritable stomachs and mouth ulcers.

Eating five portions of fruit and vegetables each day will easily meet the body's needs. Tips and advice to meet the daily requirement include:

• a bowl of strawberries contains 70-120mg of vitamin C.
• a kiwi fruit contains 50mg of vitamin C.
• a helping of steamed broccoli contains 50mg of vitamin C.
• a large orange contains 70mg of vitamin C.
• frozen or tinned fruit can be used as a source of vitamin C.
• keep the cooking time to a minimum to prevent the vitamin dissolving into the water. If possible eat the food raw or lightly steamed.

Vitamin D

This vitamin is also known as calciferol and together with calcium is essential for healthy bones and teeth.

The body manufactures vitamin D in the skin in the presence of sunlight. Hence it is important to expose the body to fresh air on a daily basis. Most people will obtain sufficient quantities of vitamin D through their everyday activities but foods rich in this vitamin are:

• butter
• cheese
• cod liver oil
• eggs
• liver
• margarine
• mackerel
• milk
• oily fish
• sardines
• tuna
• yoghurt.

Vitamin E

Vitamin E is important in cell maintenance and also plays an active role in the maintenance of a healthy cardiovascular and circulatory system. It is one of the body's main antioxidants.

The body needs a daily intake of around 3-4mg a day which can easily be obtained from eating the following fruit and vegetables rich in vitamin E:

• avocados
• blackberries
• brussels sprouts
• corn oil
• mackerel
• mangoes
• nuts
• olive oil
• tomatoes
• safflower oil
• salmon
• soft margarine
• spinach
• sunflower oil
• sweet potatoes
• watercress
• wheat germ
• wholegrain cereal.

Vitamin K

This vitamin is involved in the blood clotting process of the body and the maintenance of strong bones.

It is found in small quantities in most vegetables and wholegrain cereals, but the main source of this vitamin is from the intestinal tract and the stomach through the activity of 'healthy bacteria'. These bacteria are often also referred to as the 'gut flora'. Not only do we live in harmony with them but they in fact fulfil several important roles, including part of our defence against more harmful organisms.

Diets rich in fatty and sugary foods can adversely change the balance of the gut flora, as can the additives and pesticides that are often a part of modern food production.

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