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How important is calcium to our bones?

You will also find information on the changes that happen to bones as women age, the recommended daily calcium intake for women at different ages, the calcium content of different foods and types of calcium supplements.

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The importance of calcium

Calcium is one of the essential nutrients necessary for healthy bone development. Bones contain most of our body's calcium, so they act as the body's 'reservoir' of calcium. Calcium is critical for the function of cells in the body and a certain amount of calcium circulates within the blood, with the body maintaining the levels of calcium within a very tight range. Our bodies cannot make calcium, and if blood calcium levels fall, the body will compensate for this by drawing calcium out of bones and putting it into the blood. Calcium is also excreted by the body daily.

This means it is important to have an adequate daily intake of calcium through your diet, so your bone mineral strength is not compromised.

Jug pouring glass of cows milk

Calcium content of various foods

While dairy products can provide a good source of calcium, daily calcium requirements need not necessarily come only from dairy products. Two serves of dairy and another serve of calcium-rich foods like broccoli, beans, almonds, tinned salmon and sardines equate to about 1,000mg of calcium.

If you choose alternative calcium sources, note the quantity of calcium found within the particular food source. The following table lists the average calcium content of a variety of foods:

Food sources of calcium
Food Calcium per serve
Regular milk

Serving: 1 cup (250ml)


Calcium per serve: 285mg

Skim milk

Serving: 1 cup (250ml)


Calcium per serve: 310mg

Natural yogurt

Serving: 1 tub (200g)


Calcium per serve: 340mg

Low fat yogurt

Serving: 1 tub (200g)


Calcium per serve: 420mg

Cheddar cheese

Serving: 40g cube


Calcium per serve: 310mg

Low fat cottage cheese

Serving: 100g


Calcium per serve: 80mg

White bread

Serving: 1 slice


Calcium per serve: 15mg

Cooked spinach

Serving: 1 cup (340g)


Calcium per serve: 170mg

Cooked broccoli

Serving: 1 cup (100g)


Calcium per serve: 30mg

Canned salmon (+ bones)

Serving: ½ cup (230g)


Calcium per serve: 230mg

Canned sardines (+ bones)

Serving: 50g


Calcium per serve: 190mg

Almonds

Serving: 15 almonds


Calcium per serve: 50mg

Tofu

Serving: 100g block


Calcium per serve: 0-100mg*

* The calcium content of tofu depends on how the tofu has been processed. If it is processed using calcium chloride or calcium sulphate, tofu may have up to 100mg calcium per 100g block. Otherwise the calcium content of tofu is very low.

Calcium Counter - Reproduced with permission from Dairy Australia (as per Calcium Fact Sheet) – last updated 17/7/2002.

Calcium supplements

Calcium needs are generally best met through diet. However, calcium supplements may be required by those who do not obtain adequate calcium from food products to meet the 1,000-1,300mg per day required for girls and women.

Most calcium supplements in Australia contain:

  • calcium carbonate (sold as caltrate) or
  • calcium citrate (sold as citracal)

Calcium carbonate

Caltrate requires an acidic environment for maximum absorption and should be taken with meals.

Calcium citrate

Calcium citrate does not require an acidic environment and therefore can be taken on an empty stomach (but is better taken with food). It is the preferred calcium product for people who need to take anti-reflux medications.

When to take calcium supplements

It is best to take calcium supplements at night, as this is when bone 'turnover' increases.

High dose calcium supplements may be linked with heart disease. Beneficial effects of calcium are found with relatively low doses (500-600mg). Elderly individuals and others with impaired kidney function may be at higher risk of cardiovascular disease.

This web page is designed to be informative and educational. It is not intended to provide specific medical advice or replace advice from your health practitioner. The information above is based on current medical knowledge, evidence and practice as at December 2013.

References

  • 1
    Tran HA, Petrovsky N. Pregnancy-associated osteoporosis with hypercalcaemia. Int Med Journal 2002;32:481-5.
Last updated: 16 January 2020 | Last reviewed: 01 December 2013

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