The average adult’s weight is made up of about two per cent calcium. Most of this is found in the skeleton and teeth – the rest is stored in the tissues or blood. Calcium is vital for healthy teeth and bones. It also plays a crucial role in other systems of the body, such as the health and functioning of nerves and muscle tissue.
Good sources of calcium include dairy foods like milk, yoghurt and cheese, and calcium-fortified products, such as soymilk or rice drink and breakfast cereals. People at different life stages need different amounts of calcium – young children, teenagers and older women all have greater than average requirements.
According to the most recent Australian Nutrition Survey data published in 1995, about 90 per cent of women and 70 per cent of children do not achieve the recommended dietary intake (RDI) for calcium. Data from the National Nutrition Survey 2011-12 will be released later in 2014.
It is much better to get calcium from foods than from calcium supplements. Be guided by your doctor about whether you need additional supplements. Too much calcium (2,000 mg or more) from supplements may cause other health problems.
Role of calcium in the body
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
Australians receive most of their 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 disease of both men and women in which bones become fragile and brittle later in life).
Too little calcium can weaken bones
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, 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
The recommended dietary intake of calcium is different for people of different ages and life stages, including:
People with special calcium needs
It is particularly important that people from certain groups meet their calcium needs. These groups include:
- Babies – formula-fed babies are estimated to need more than babies that are breastfed, because the calcium in infant formula may not be absorbed as efficiently as that found in breastmilk.
- Young children – skeletal tissue is constantly growing, so young children have high calcium requirements.
- Pre-teens and teenagers – puberty prompts a growth spurt. This group also needs more calcium to build peak bone mass. If the skeleton is strengthened with enough calcium during these years, diseases like osteoporosis in the later years are thought to be less likely.
- Early 20s to mid-life – sufficient dietary calcium is required to maintain bone mass, although the amount of calcium required is less than during growth stages of life.
- Pregnant women – a developing baby needs a lot of calcium. However there is no need for women to take additional dietary calcium during pregnancy because pregnant women absorb calcium from food more efficiently.
- Breastfeeding women – there is no increased requirement for calcium during breastfeeding, except for breastfeeding adolescents.
- Elderly people – as we age, the skeleton loses calcium. Women lose more calcium from their bones in the five to 10 years around the age of menopause. However, both men and women lose bone mass as they grow older and need to make sure they get enough calcium in their diet to offset these losses. While a diet high in calcium cannot reverse age-related bone loss, it can slow down the process.
- Caucasian (white) people – have larger frame sizes and generally have higher intakes of animal foods, caffeine and salt. It is thought they may need more calcium than non-Caucasian people who often have smaller frame sizes.
Good sources of calcium
Good dietary sources of calcium include:
- milk and milk products – milk, yoghurt, cheese and buttermilk. One cup of milk, a 200 g tub of yoghurt or 200 ml of calcium-fortified soymilk provides around 300 mg calcium. Calcium-fortified milks can provide larger amounts of calcium in a smaller volume of milk – ranging from 280 mg to 400 mg per 200 ml milk.
- leafy green vegetables – broccoli, collards (cabbage family), bok choy, Chinese cabbage and spinach. One cup of cooked spinach contains 100 mg, although only five per cent of this may be absorbed. This is due to the high concentration of oxalate, a compound in spinach that reduces calcium absorption. By contrast, one cup of cooked broccoli contains about 45 mg of calcium, but the absorption from broccoli is much higher at around 50–60 per cent.
- soy and tofu – tofu (depending on type) or tempeh and calcium fortified soy drinks
- fish – sardines and salmon (with bones). Half a cup of canned salmon contains 402 mg of calcium
- nuts and seeds – brazil nuts, almonds and sesame seed paste (tahini). Fifteen almonds contain about 40 mg of calcium.
- calcium-fortified foods – including breakfast cereals, fruit juices and bread. One cup of calcium-fortified breakfast cereal (40 g) contains up to 200 mg of calcium. ½ cup of calcium-fortified orange juice (100 ml) contains up to 80 mg of calcium, and two slices of bread (30 g) provides 200 mg of calcium.
It is much better to get calcium from foods (which also provide other nutrients) than from calcium supplements. If you have difficulty eating enough foods rich in calcium, you might need to consider a calcium supplement, especially if you are at risk of developing osteoporosis. It’s a good idea to discuss this with your doctor or other registered healthcare professional.
If you do take calcium supplements, make sure you don’t take more than the amount recommended on the bottle. Too much calcium may cause gastrointestinal upsets, such as bloating and constipation.
Calcium supplements and heart disease risk
A report published in 2010, and widely reported in the media, found a possible link between calcium supplements and an increased risk of heart disease – particularly in older women. The levels of calcium intake of participants in the trials reviewed were up to 2,400 mg a day, achieved by taking supplements. (The RDI is between 1,000 and 1,300 mg per day for adults depending on age.)
Calcium intake at levels of 2,000 mg or more through supplementation may be of concern. This area requires further research, but currently associations such as Osteoporosis Australia and the British Heart Foundation recommend continuing calcium supplementation if recommended by your doctor, and suggest that you discuss any concerns you may have with your registered healthcare professional.
Lifestyle can affect bone strength
Some of the factors that can reduce calcium in your bones and lower bone density (weaken 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
- very low body weight
- very high intakes of fibre (more than 50 g per day, from wheat bran)
- low levels of physical activity
- low levels of vitamin D – people who are housebound or cover their bodies completely when they are outside are at increased risk
Where to get help
- Your doctor
- Dietitians Association of Australia Tel. 1800 812 942
- Nutrition Australia
Things to remember
- The average adult’s weight is made up of about two per cent calcium.
- Good sources of calcium include dairy foods like milk, yoghurt and cheese, calcium fortified foods (such as soy products) and, to a lesser degree, some leafy green vegetables.
- If you don’t have enough calcium in your diet, you may be at increased risk of developing osteoporosis.
This page has been produced in consultation with and approved by:
Deakin University - School of Exercise and Nutrition Sciences
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