Attainment of peak bone mass is dependent on ensuring adequate levels of dietary calcium, exercise and normal levels of growth hormones and gonadal hormones in childhood and adolescence.

Calcium Intake

Tables of recommended dietary intakes of calcium for use in Australia are given below for various age groups. These tables are derived from the National Health and Medical Research Council and are to be revised in late 2005.

	Recommended daily calcium intake
	Category Age (years) Calcium (mg) Children 1-3 500   4-8 700  Girls 9-11 1000   12-18 1300 Women 19-50 1000   >50 1300 Pregnancy/Lactation: 14-18 1300   19-30 1000   31-50  1000 Boys 9-11  1000   12-18 1300 Men 19-70 1000   >70 1300 Source:26National Health and Medical Research Council. (2006) Executive Summary of Nutrient Reference Values for Australia and New Zealand Including Recommended Dietary Intakes. Commonwealth Department of Health and Aging, Australia, Ministry of Health, New Zealand.

Premenopausal Years

During childhood and adolescence, when the skeleton is actively growing it is essential that calcium intake meets the requirements of the growing skeleton. It is during this growth phase that the foundations for the attainment of peak bone mass are laid. Peak bone mass is achieved by the third decade of life (early 20’s).³

It is also important to ensure that in the premenopausal years, that women have adequate calcium intake, particularly during periods of growth and during the reproductive milestones.

Pregnancy and Breastfeeding

Pregnant women and lactating women need to have adequate calcium intake. In pregnancy, especially in the third trimester of pregnancy, calcium requirements are increased, in order to meet the requirements for bone mineralization in the foetal skeleton. Lactating women also have high requirements for calcium in order to allow for milk production.

Normal pregnancy and lactation beyond 6 months is associated with a 2 – 5% loss of bone mineral density, which generally recovers 6 – 12 months after the cessation of pregnancy and/or lactation.³⁰ There are very rare instances of pregnant and lactating women developing osteoporosis and fractures, but usually this is in the setting of pre-existing conditions, which predispose the individual to osteoporosis.³⁰

Postmenopausal Years

In middle age women the ability to adequately absorb calcium from the gut and kidney is diminished due to the effects of oestrogen deficiency. This results in a compensatory increase in parathyroid hormone so as to maintain serum calcium levels in the normal range. This can subsequently worsen bone loss in postmenopausal women, in addition to the effects of oestrogen deficiency on bone. To offset this process, postmenopausal women need to have approximately 1300 mg of calcium per day. This is equivalent to 4 serves of dairy products per day.

For many middle aged women their dietary intake of calcium is suboptimal with 30 – 60% of Australian postmenopausal women failing to meet requirements for recommended dietary intake of calcium.^27,28 This is often due to a preference for avoiding dairy foods due to concerns about fat and cholesterol content, underlying lactose intolerance or lifelong dislike of dairy products.²⁸ In this setting it may be necessary to prescribe calcium supplementation either in the form of calcium carbonate or calcium citrate.

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Calcium Supplementation

Most calcium supplements in Australia are in the form of calcium carbonate (e.g. caltrate) or calcium citrate (e.g. citrocal). Although the doses of calcium in these two preparations are different, the actual amount of calcium which is absorbed is the same. However, for women taking antacids or anti-reflux medication it is preferable to take calcium citrate as the absorption of calcium is more efficient than from calcium carbonate.

Calcium supplementation has been found to have a small effect on improving bone mineral density. In a recent meta-analysis on the effects of calcium supplementation in postmenopausal women, there was a trend towards there being a reduction in vertebral fractures, although pooled data did not reach statistical significance.²⁹

There are few studies available on non-vertebral fracture risk with calcium supplementation, to make any meaningful assessment on fracture risk.²⁹

Despite the lack of conclusive findings with regards to the effects of calcium supplementation on fracture risk (trend towards reducing vertebral fracture risk), it is clear that calcium supplementation does increase bone mineral density.²⁹ This effect of calcium supplementation has important additive effects when combining calcium with other osteoporosis therapies such as vitamin D or bisphosphonates.

Recently, studies in older women suggest one gram of calcium supplement (more than one tablet daily) may increase the risk of heart disease. Further research is needed.

Content updated February 26, 2008