NHS Direct Wales - Encyclopaedia : Vitamins and minerals

Vitamins and minerals are essential nutrients that your body needs in small amounts to work properly.

Most people should be able to get all the nutrients they need by eating a varied and balanced diet. If you choose to take vitamin and mineral supplements, be aware that taking too much or taking them for too long can cause harmful effects.

The pages in this section contain all the advice and information that adults need about the vitamins, minerals and trace elements that are essential for health, including:

what they do
how much you need
what happens if you have too much
safety advice about supplements

What are vitamins?

There are two types of vitamins: fat-soluble and water-soluble.

Fat-soluble vitamins

Fat-soluble vitamins are found mainly in fatty foods such as animal fats including butter and lard, vegetable oils, dairy foods, liver and oily fish.

While your body needs these vitamins every day to work properly, you do not need to eat foods containing them every day.

This is because, if your body does not need these vitamins immediately, it stores them in your liver and fatty tissues for future use. These stores can build up so they are there when you need them. However, if you have much more than you need, fat-soluble vitamins can be harmful.

Fat-soluble vitamins are:

Water-soluble vitamins

Water-soluble vitamins are not stored in the body, so you need to have them more frequently.

If you have more than you need, your body gets rid of the extra vitamins when you urinate. Because the body does not store water-soluble vitamins, these vitamins are generally not harmful.

Water-soluble vitamins are found in fruit, vegetables and grains. Unlike fat-soluble vitamins, they can be destroyed by heat or by being exposed to the air. They can also be lost in water used for cooking.

This means that by cooking foods, especially boiling them, we lose many of these vitamins. The best way to keep as much of the water-soluble vitamins as possible is to steam or grill these foods, rather than boil them.

Water-soluble vitamins are vitamin C, the B vitamins and folic acid.

What are minerals?

Minerals are necessary for three main reasons:

building strong bones and teeth
controlling body fluids inside and outside cells
turning the food you eat into energy

You need minerals in the form they are found in food.

Minerals are found in varying amounts in foods such as meat, cereals including cereal products such as bread, fish, milk and dairy foods, vegetables, fruit (especially dried fruit) and nuts.

Essential minerals include calcium and iron.

What are trace elements?

Trace elements are also essential nutrients that your body needs to work properly, but in much smaller amounts than vitamins and minerals.

Trace elements are found in small amounts in a variety of foods such as meat, fish, cereals, milk and dairy foods, vegetables and nuts.

Examples of trace elements are fluoride and iodine.

This section has information on:

vitamin B6
vitamin B12
niacin (vitamin B3)
pantothenic acid
riboflavin (vitamin B2)
thiamin (vitamin B1)
folic acid (one of the B-group vitamins)

Vitamin B6

Vitamin B6 is also known as pyridoxine. It has several important functions, including:

allowing the body to use and store energy from protein and carbohydrates in food
helping form haemoglobin, the substance that carries oxygen around the body

Good sources of vitamin B6

Vitamin B6 is found in a wide variety of foods such as:

pork
chicken
turkey
cod
bread
whole cereals, such as oatmeal, wheat germ and rice
eggs
vegetables
soya beans
peanuts
milk
potatoes
some fortified breakfast cereals

How much vitamin B6 do I need?

The amount of vitamin B6 you need is about:

1.4mg a day for men
1.2mg a day for women

You should be able to get all the vitamin B6 you need from your daily diet. You need it in your diet every day because it cannot be stored in the body.

What happens if I take too much vitamin B6?

Taking more than 200mg a day of vitamin B6, or taking large amounts for a long time, can lead to a loss of feeling in the arms and legs, known as peripheral neuropathy.

Generally, the symptoms are reversible, so once you stop taking supplements, the symptoms usually stop.

However, in a few cases when people have taken large amounts of vitamin B6, especially for more than a few months, the effect has been irreversible.

Taking doses of 10-200mg a day for short periods may not cause any harm. However, there is not enough evidence to say for how long these doses could be taken safely.

What does the Department of Health advise?

You should be able to get the vitamin B6 you need by eating a varied and balanced diet. If you take vitamin B6 supplements, do not take too much because this could be harmful.

Do not take more than 10mg of vitamin B6 a day in supplements. However, continue taking a higher dose if advised to by a doctor.

Vitamin B12

Vitamin B12 has several important functions and is involved in:

making red blood cells and keeping the nervous system healthy
releasing energy from the food we eat
processing folic acid

A lack of vitamin B12 could lead to vitamin B12 deficiency anaemia.

Good sources of vitamin B12

These include:

meat
salmon
cod
milk
cheese
eggs
yeast extract
some fortified breakfast cereals

How much vitamin B12 do I need?

Adults need approximately 0.0015mg a day of vitamin B12.

If you eat meat, fish or dairy foods, you should be able to get enough vitamin B12 from your diet.

However, because vitamin B12 is not found in foods such as fruit, vegetables and grains, vegans may not get enough of this vitamin.

What happens if I take too much vitamin B12?

There is not enough evidence to show what the effects may be of taking high doses of vitamin B12 supplements each day.

What does the Department of Health advise?

You should be able to get all the vitamin B12 you need by eating a varied and balanced diet. If you take vitamin B12 supplements, do not take too much because this could be harmful.

Taking 2mg or less a day of vitamin B12 in supplements is unlikely to cause any harm.

Niacin (vitamin B3)

Niacin is also known as vitamin B3. It has several important functions, including:

helping produce energy from the foods we eat
helping keep the nervous and digestive systems healthy

Good sources of niacin

Good sources of niacin include:

meat
fish
wheat flour
maize flour
eggs
milk

How much niacin do I need?

The amount of niacin you need is about:

17mg a day for men
13mg a day for women

You should be able to get all the niacin you need from your daily diet.

There are two forms of niacin - nicotinic acid and nicotinamide - both of which are found in food. Niacin cannot be stored in the body, so you need it in your diet every day.

What happens if I take too much niacin?

Taking high doses of nicotinic acid supplements can cause skin flushes. Taking high doses for a long time could lead to liver damage.

There is not enough evidence to know what the effects might be of taking high daily doses of nicotinamide supplements.

What does the Department of Health advise?

You should be able to get the amount of niacin you need by eating a varied and balanced diet. If you take niacin supplements, do not take too much because this might be harmful.

Taking 17mg or less of nicotinic acid supplements a day or 500mg or less of nicotinamide supplements a day is unlikely to cause any harm.

Pantothenic acid

Pantothenic acid has several functions, such as helping release energy from the food we eat.

Good sources of pantothenic acid

Pantothenic acid is found in virtually all meat and vegetable foods. Good sources include:

chicken
beef
potatoes
porridge
tomatoes
kidney
eggs
broccoli
wholegrains, such as brown rice and wholemeal bread

Breakfast cereals are also a good source if they have been fortified with pantothenic acid.

How much pantothenic acid do I need?

You should be able to get all the pantothenic acid you need from your daily diet.

Pantothenic acid cannot be stored in the body, so you need it in your diet every day.

What happens if I take too much pantothenic acid?

There is not enough evidence to know what the effects might be of taking high daily doses of pantothenic acid supplements.

What does the Department of Health advise?

You should be able to get all the pantothenic acid you need by eating a varied and balanced diet. If you take supplements, do not take too much because this might be harmful.

Taking 200mg or less a day of pantothenic acid in supplements is unlikely to cause any harm.

Riboflavin (vitamin B2)

Riboflavin is also known as vitamin B2. Its functions include:

keeping skin, eyes and the nervous system healthy
producing steroids and red blood cells

Good sources of riboflavin

Good sources of riboflavin include:

milk
eggs
fortified breakfast cereals
rice
mushrooms

UV light can destroy riboflavin, so ideally these foods should be kept out of direct sunlight.

How much riboflavin do I need?

The amount of riboflavin you need is about:

1.3mg a day for men
1.1mg a day for women

Riboflavin cannot be stored in the body, so you need it in your diet every day.

You should be able to get all the riboflavin you need from your daily diet.

What happens if I take too much riboflavin?

There is not enough evidence to know what the effects might be of taking high doses of riboflavin supplements each day.

What does the Department of Health advise?

You should be able to get all the riboflavin you need by eating a varied and balanced diet. If you take supplements, do not take too much because this might be harmful.

Taking 40mg or less a day of riboflavin supplements is unlikely to cause any harm.

Thiamin (vitamin B1)

Thiamin is also known as vitamin B1. It has several important functions, including:

working with other B-group vitamins to help break down and release energy from food
keeping nerves and muscle tissue healthy

Good sources of thiamin

Thiamin is found in most types of food. Good sources include:

pork
vegetables
milk
cheese
peas
fresh and dried fruit
eggs
wholegrain breads
some fortified breakfast cereals

How much thiamin do I need?

The amount of thiamin you need is:

1mg a day for men
0.8mg a day for women

You should be able to get all the thiamin you need from your daily diet.

Thiamin cannot be stored in the body, so you need it in your diet every day.

What happens if I take too much thiamin?

There is not enough evidence to know what the effects might be of taking high doses of thiamin supplements each day.

What does the Department of Health advise?

You should be able to get all the thiamin you need by eating a varied and balanced diet. If you take supplements, do not take too much because this might be harmful.

Taking 100mg or less a day of thiamin supplements is unlikely to cause any harm.

Folic acid

Folic acid, known as folate in its natural form, is one of the B-group vitamins.

Folate has several important functions. For example, it:

works together with vitamin B12 to form healthy red blood cells
helps reduce the risk of central nervous system defects such as spina bifida in unborn babies

A lack of folate could lead to folate deficiency anaemia.

Good sources of folate

Folate is found in small amounts in many foods. Good sources include:

broccoli
brussels sprouts
asparagus
peas
chickpeas
brown rice
fortified breakfast cereals

How much folate do I need?

Adults need 0.2mg of folate a day.

Folate cannot be stored in the body, so you need it in your diet every day.

Most people should be able to get the amount they need by eating a varied and balanced diet.

However, if you are pregnant or thinking of having a baby, take a daily 0.4mg (400 microgram) of folic acid supplement from the time you stop using contraception until the 12th week of pregnancy. This is to help prevent birth defects of the central nervous system, such as spina bifida, in your baby.

Women who have had a pregnancy affected by a neural tube defect need to take 5mg of folic acid each day until the 12th week of pregnancy. This is available on prescription from your GP. Women with diabetes and those taking anti-epileptic medicines should speak to their GP for advice.

What happens if I take too much folic acid?

If you do not get enough vitamin B12, taking doses of folic acid higher than 1mg can disguise the effects of this.

An early symptom of vitamin B12 deficiency is anaemia. However, taking large amounts of folic acid treats the anaemia without treating the B12 deficiency. If a vitamin B12 deficiency is not noticed, it can eventually damage the nervous system.

This is particularly a concern for older people because it becomes more difficult to absorb vitamin B12 as you get older.

What does the Department of Health advise?

The Department of Health recommends that folic acid supplements are taken by women who are pregnant or thinking of having a baby (see 'How much folate do I need?', above).

Women who are not pregnant or planning for a baby should be able to get all the folate they need by eating a varied and balanced diet.

If you are taking folic acid supplements, it is important not to take too much because this could be harmful.

Taking 1mg (1,000 micrograms) or less a day of folic acid supplements is unlikely to cause any harm.

Vitamin C is also know as ascorbic acid. It has several important functions. For example, it:

helps protect cells and keeps them healthy
is necessary for the maintenance of healthy connective tissue, which gives support and structure for other tissue and organs

A lack of vitamin C can lead to scurvy.

Good sources of vitamin C

Vitamin C is found in a wide variety of fruit and vegetables. Good sources include:

peppers
broccoli
brussels sprouts
sweet potatoes
oranges
kiwi fruit

How much vitamin C do I need?

Adults need 40mg of vitamin C a day.

Vitamin C cannot be stored in the body, so you need it in your diet every day.

You should be able to get all the vitamin C you need from your daily diet.

What happens if I take too much vitamin C?

Taking large amounts of vitamin C can cause:

stomach pain
diarrhoea
flatulence

These symptoms should disappear once you stop taking vitamin C supplements.

What does the Department of Health advise?

You should be able to get all the vitamin C you need by eating a varied and balanced diet. If you take vitamin C supplements, do not take too much because this could be harmful.

Taking 1,000mg or less a day of vitamin C supplements is unlikely to cause any harm.

Vitamin D has several important functions. For example, it helps regulate the amount of calcium and phosphate in the body. These substances are needed to keep bones and teeth healthy.

If you do not get enough vitamin D, you might be more at risk of some of the harmful effects of too much vitamin A. Ask your GP for more information.

A lack of vitamin D can also lead to rickets.

Good sources of vitamin D

Most of our vitamin D comes from sunlight on our skin. The vitamin forms under the skin in reaction to sunlight. The best source is summer sunlight. However, if you are out in the sun, take care not to turn red or get burnt.

Vitamin D is also found in a small number of foods. Good food sources are:

oily fish, such as salmon and sardines
eggs
fortified fat spreads
fortified breakfast cereals
powdered milk

How much vitamin D do I need?

You do not need vitamin D in your diet every day. This is because any of the vitamin your body does not need immediately is stored for future use.

Most people should be able to get all the vitamin D they need by eating a healthy balanced diet and by getting some sun.

However, the Department of Health recommends that the following people take daily vitamin D supplements:

all children aged six months to five years old
all pregnant and breastfeeding women
all people aged 65 and over
people who are not exposed to much sun, such as people who cover up their skin for cultural reasons or those who are housebound or confined indoors for long periods
people with darker skins such as people of African-Caribbean and South Asian origin

What happens if I take too much vitamin D?

Taking high doses of vitamin D for long periods of time could weaken your bones.

What does the Department of Health advise?

Most people should be able to get the vitamin D they need by eating a varied and balanced diet and by getting some sun. If you take vitamin D supplements, do not take too much.

Taking 25 micrograms (0.025mg) or less a day of vitamin D supplements is unlikely to cause any harm.

The Department of Health recommends that certain people should take vitamin D supplements (see above).

Vitamin E has several important functions. For example, it helps protect cell membranes.

Good sources of vitamin E

Vitamin E is found in a wide variety of foods. The richest sources are plant oils such as soya, corn and olive oil.

Other good sources include:

nuts and seeds
wheat germ, found in cereals and cereal products

How much vitamin E do I need?

The amount of vitamin E you need is:

4mg a day for men
3mg a day for women

You should be able to get all the vitamin E you need from your daily diet.

Any vitamin E that your body does not need immediately is stored for future use, so you do not need it in your diet every day.

What happens if I take too much vitamin E?

There is not enough evidence to know what the effects might be of taking high doses of vitamin E supplements each day.

What does the Department of Health advise?

You should be able to get the amount of vitamin E you need by eating a varied and balanced diet. If you take vitamin E supplements, do not to take too much.

Taking 540mg or less a day of vitamin E supplements is unlikely to cause any harm.

Vitamin K has several important functions. For example, it is needed for blood clotting, which means it helps wounds heal properly.

There is increasing evidence that vitamin K is also needed to help build strong bones.

Good sources of vitamin K

Vitamin K is found in:

green leafy vegetables, such as broccoli and spinach
vegetable oils
cereals

Small amounts can also be found in meat and dairy foods.

As well as getting vitamin K from food, we also get it from our own bodies as it is produced by bacteria in the bowel.

How much vitamin K do I need?

Adults need approximately 0.001mg a day of vitamin K for each kilogram of their body weight.

For example, someone who weighs 65kg would need 0.065mg a day of vitamin K, while a person who weighs 75kg would need 0.075mg a day.

You should be able to get all the vitamin K you need by eating a varied and balanced diet.

Any vitamin K that your body does not need immediately is stored in the liver for future use, so you do not need it in your diet every day.

What happens if I take too much vitamin K?

There is not enough evidence to know what the effects might be of taking high doses of vitamin K supplements each day.

What does the Department of Health advise?

You should be able to get all the vitamin K you need by eating a varied and balanced diet. If you take vitamin K supplements, do not take too much because this might be harmful.

Taking 1mg or less of vitamin K supplements a day is unlikely to cause any harm.

Calcium has several important functions, including:

helping build strong bones and teeth
regulating muscle contractions, including heartbeat
ensuring blood clots normally

It is thought that calcium may help lower high blood pressure and protect against colon and breast cancer, although more evidence is needed to confirm this.

A lack of calcium could lead to a condition called rickets.

Good sources of calcium

Good sources of calcium include:

milk, cheese and other dairy foods
green leafy vegetables, such as broccoli, cabbage and okra, but not spinach
soya beans
tofu
soya drinks with added calcium
nuts
bread and anything made with fortified flour
fish where you eat the bones, such as sardines and pilchards

How much calcium do I need?

Adults need 700mg of calcium a day.

You should be able to get all the calcium you need from your daily diet.

What happens if I take too much calcium?

Taking high doses of calcium could lead to stomach pain and diarrhoea.

What does the Department of Health advise?

You should be able to get all the calcium you need by eating a varied and balanced diet. If you take calcium supplements, do not take too much.

Taking 1,500mg or less a day of calcium supplements is unlikely to cause any harm.

Iodine helps make the thyroid hormones. These hormones help keep cells and the metabolic rate healthy.

Good sources of iodine

Iodine is a trace element found in seawater, rocks and some types of soil. Good food sources include sea fish and shellfish.

Iodine can also be found in plant foods such as cereals and grains, but the levels vary depending on the amount of iodine in the soil where the plants are grown.

In the UK, iodine can also be found in cows' milk.

How much iodine do I need?

Adults need 0.14mg of iodine a day.

You should be able to get all the iodine you need by eating a varied and balanced diet.

What happens if I take too much iodine?

Taking high doses of iodine for long periods of time could change the way your thyroid gland works. This can lead to a wide range of different symptoms, such as weight gain.

What does the Department of Health advise?

You should be able to get all the iodine you need by eating a varied and balanced diet. If you take iodine supplements, do not take too much because this could be harmful.

Taking 0.5mg or less a day of iodine supplements is unlikely to cause any harm.