When we think of calcium, what springs to mind are teeth, bones and cows milk. While calcium is certainly related to these things, the mineral is required for many more processes in our bodies and is found in an array of healthy foods.
To find out everything about calcium, including why we need it and where we can find it, HuffPost Australia spoke to two health experts.
What is calcium and why do we need it?
"Calcium is a mineral and facilitates a number of functions in the body, including bone and tooth formation, muscle contraction and nerve transmission," nutritionist Zoe Bingley-Pullin told HuffPost Australia. "It also regulates heart rhythm and plays a role in electrolyte balance."
Calcium plays a role in:
- strengthening bones and teeth
- regulating muscle functioning (such as contraction and relaxation)
- regulating heart functioning and blood clotting
- regulating the transmission of nervous system messages and enzyme functions.
Interestingly, calcium is the most abundant mineral in the human body and is stored in our teeth and bones.
How much calcium do we need per day?
"The amount of calcium we require does change as we age," accredited practising dietitian and performance dietitian Jessica Spendlove told HuffPost Australia.
"Calcium requirements are at their highest for men and women during adolescence when we are developing peak bone mass, and then also later in life when bone mass is naturally declining.
"For women, this is at the onset of menopause (typically in their 50s) and for men this is once they hit their 70s."
What happens when we're calcium deficient?
"Calcium deficiency may cause or be associated with a number of health conditions such as heart palpitations, tooth decay, poor bone mineral density and osteoporosis, muscular cramps, depression and stunted growth," Bingley-Pullin said.
Osteoporosis is quite common in western cultures and often results in bone fractures, Spendlove explained.
"When the body notices there is not enough calcium circulating in the blood, it will use hormones to reduce the amount excreted 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."
Osteoporosis is one of the major causes of morbidity amongst older Australians and New Zealanders, particularly postmenopausal women.
"Calcium intake throughout life is a major factor affecting the incidence of osteoporosis -- however, other factors, notably adequate vitamin D status and exercise, also play a role," Spendlove said.
What foods are high in calcium?
Calcium is found in many foods, including animal and plant-based products.
"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, nuts, seeds and fish," Spendlove said.
Good dietary sources of calcium and recommended doses:
- Dairy products including milk, yoghurt, cheese and buttermilk -- 300mg equates to roughly 250ml of milk, 200g tub of yoghurt, 250ml of calcium-fortified soy or plant milk, or 40g of cheddar cheese
- Leafy green vegetables including broccoli, collards (cabbage family), bok choy, Chinese cabbage and spinach -- 100mg equates to roughly one cup of cooked spinach, although not all of this may be absorbed (due to the high concentration of oxalate, a compound in spinach that reduces calcium absorption); 45mg equates to roughly one cup of cooked broccoli, but the absorption from broccoli is much higher at around 50–60 per cent.
Other notable sources of calcium include:
- Soy and tofu
- Fish -- sardines and salmon (with bones); half a cup of canned salmon contains 402mg of calcium
- Nuts and seeds -- brazil nuts, almonds and sesame seed paste (tahini). Fifteen almonds contain about 40mg of calcium.
- Calcium-fortified foods -- including breakfast cereals, fruit juices and bread. One cup of calcium-fortified breakfast cereal (40g) contains up to 200mg of calcium -- ½ cup of calcium-fortified orange juice (100ml) contains up to 80mg of calcium; two slices of bread (30g) provides 200mg of calcium.
Are calcium supplements beneficial?
Before considering a calcium supplement, it's important to check in with a GP to assess your calcium and vitamin D levels by way of bone mineral density scans, blood tests, food diary and/or symptoms.
"It's important to assess vitamin D status as well because vitamin D helps to regulate the absorption of calcium," Bingley-Pullin said.
"It is much better to get calcium from foods (which also provide other nutrients) than from calcium supplements," Spendlove said.
"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."