Calcium

The average adult's weight is made up of about two per cent calcium. The bulk of this mineral is found in the skeleton and teeth; the rest is stored in the tissues or blood. Calcium is vital for healthy teeth and bones and also plays a crucial role in human body, such as the health and functioning of nerves and muscle tissue.

Good sources of calcium include dairy foods and leafy green vegetables, although calcium from milk and milk products is more easily absorbed and present in greater amounts. People at different life stages need different amounts of calcium – young children, teenagers and older women all have greater than average requirements.

Calcium plays a role in:

Strengthening bones and teeth

Regulating muscle functioning, such as contraction and relaxation

Regulating heart functioning

Blood clotting

Transmission of nervous system messages

Enzyme function.

Calcium and dairy food : We receive most of the calcium from dairy foods. If milk is removed from the diet, it can lead to an inadequate intake of calcium. This is of particular concern for children and adolescents, who have high calcium needs. Calcium deficiency may lead to disorders like osteoporosis (a degenerative disease characterised by bone loss that occurs in men and women later in life).

Blood calcium takes priority : If the body notices that not enough calcium is circulating in the blood, it will use hormones to reduce the amount put out by the kidneys in the urine. If not enough calcium is absorbed through the gastrointestinal tract then calcium will be taken from the bones. If your dietary intake of calcium is constantly low, your body will eventually remove so much calcium from the skeleton that your bones will become weak and brittle.

Calcium needs vary throughout life: Average calcium requirements through different life stages include:

Young children – skeletal tissue is constantly growing, so young children have high calcium needs. Babies need 300mg per day if breast fed and 500mg per day if bottle fed, while children (up to the age of 11 years) need around 700–900mg per day.

Pre-teens and teenagers – puberty prompts a growth spurt. This group needs more calcium, between 1,000 and 1,200mg per day. Peak bone mass years – from puberty to around the mid-20s, the skeleton increases its bone mass. If the skeleton is fortified with enough calcium during these years, diseases like osteoporosis in the later years are less likely.

During mid-life women and men need around 800mg per day. Pregnant women – although a developing baby needs a lot of calcium, which is taken from the mother's bones, most women rapidly replace this bone loss once the baby has stopped breastfeeding. The mother should make sure she has enough calcium in her diet during pregnancy, as this may protect her bone mass while also meeting the needs of the foetus.

Breastfeeding women – a breastfeeding mother needs enough calcium for her needs and her baby's needs, which is around 1,200mg per day.

Elderly people – as we age, the skeleton loses calcium. Women lose the most calcium from their bones in the five years around the age of menopause. However, both men and women lose bone mass as they grow older and should increase the amount of calcium in their diet (1,000mg per day). While a diet high in calcium cannot reverse age-related bone loss, it can slow down the process.

Good dietary sources of calcium include:

Milk and milk products – milk, yoghurt, cheese and buttermilk. One cup of milk or a 200g tub of yoghurt provides around 300mg calcium.

Leafy green vegetables – broccoli, collards, bok choy, Chinese cabbage and spinach. One cup of cooked spinach contains 100mg. One cup of cooked broccoli contains about 45mg.

Soya and calcium fortified soya drinks.

Fish – sardines and salmon (with bones).

Nuts and seeds almonds and sesame seed paste

Lifestyle factors can reduce calcium in your bones include:

High salt diet

More than six drinks per day of caffeine-containing drinks – for example coffee, cola and tea (although tea has less caffeine)

Excessive alcohol intake

Excessive intake of phosphate-containing foods that do not contain calcium, for example soft drinks

Very low body weight

Low levels of physical activity

Low levels of vitamin D – this may be an issue for people who are housebound or for women who cover their bodies completely when they are outside, as they do not get enough sunlight on their skin.

Things to remember

The average adult's weight is made up of about two per cent calcium.

Good sources of calcium include dairy foods, fortified food products such as some breakfast cereals, soy products and, to a lesser degree, leafy green vegetables. Calcium from milk and milk products may be absorbed more readily.

If you don't have enough calcium in your diet, you may get osteoporosis.