Calcium

Calcium is the principal mineral in bones and teeth and is responsible for bone formation and structure throughout life. Calcium is also important in nerve and muscle activity.

The absorption and excretion of calcium in the body is controlled by hormones and Vitamin D. An inadequate supply of calcium in the body is closely related to an inadequate supply of Vitamin D. A deficiency of Vitamin D causes a weakening of bones, which can lead to a disease called rickets in children or osteomalacia in adults.

Recommended daily intakes (RDI) for calcium (mg/day)

 

Age (years)

Men

Up to 70 years

1000 mg/day

 

Over 70 years

1300 mg/day

Women

Up to 50 years

1000 mg/day

 

Over 50 years

1300 mg/day

When the most recent National Nutrition Survey was completed in New Zealand, the average daily intake of calcium was 766 mg and it was estimated that 80% of New Zealanders were consuming enough calcium.

Food sources of calcium

The amount of calcium present in foods varies greatly and people can find it hard to consume enough calcium to meet the Recommended Daily Intake (RDI) requirements. The best food sources of calcium are milk, cheese, yoghurt, dairy foods, nuts, fish with bones, broccoli and dried fruit. Although dairy foods are an excellent source of calcium, butter and cream are not good sources because of the high fat content of these foods.

Some foods contain components which bind to calcium making it unavailable for absorption in the body. People on high-fibre diets should include dairy sources in their eating plans, because fibre binds to calcium and decreases absorption. For people who are unable to consume dairy foods, owing to dietary restrictions, (e.g. lactose intolerance) calcium supplement tablets may be recommended by a medical professional.

Bread and calcium

Bread contributes 6% of the calcium in our diet. All breads supply calcium, although white bread is a better source of calcium as it does not contain the phytates present in wholegrain breads which can bind to calcium and decrease its availability. However, mixed-grain breads are now available with added calcium, for example, Molenberg Vital (contains soy, linseed and calcium) and Tip Top UP HiFibre and calcium.

Osteoporosis

At the age of 30, people reach their peak bone mass. Therefore it is important that enough calcium has been consumed in the diet before the age of 30 as this will provide the basis of bone health later in life. After the age of 40, some losses of calcium begin to occur and with time, bone mass slowly decreases. If severe losses of calcium occur the bones will become weak, brittle and easily broken. This condition is known as osteoporosis and is most common in post-menopausal women, but can also occur in young people and men.

It is essential that everyone, especially adolescents and older women, ensures that their diets provide a good calcium intake. In addition doing weight bearing exercise for 30 minutes a day (e.g. walking) and having sufficient Vitamin D levels in the body (best Vitamin D source is the sun) are ways of decreasing the risks of osteoporosis.

For more information on osteoporosis visit the website of Osteoporosis New Zealand www.bones.org.nz.

Research is currently underway to confirm calcium’s positive role in protecting against bowel and breast cancers.