Ladies, You Can Go Easy on the Calcium

Fractures due to osteoporosis are quite common in the elderly, especially in women, and the role of calcium intake in prevention is by no means clear.  There’s a wide range in the recommendations for daily calcium intake in different countries, e.g. 700 mg in the UK, 800 mg in Scandinavia, 1,200 mg in  the USA, and 1,300 mg in Australia and New Zealand.  Progress has been shown, however, in results from a Swedish study reported in the British Medical Journal.

A group of more than 60,000 women born between 1914 and 1948 were followed for an average of 19 years; calcium intake was estimated from repeated food frequency questionnaires, and 5,022 of them had bone mineral density (BMD) measured, using dual energy X-ray absorptiometry.  All fractures occurring during follow-up were recorded.  

There were almost 15,000 women (24%) who had a first fracture of any type, and 6% who had hip fractures; osteoporosis was diagnosed in 20% of those subjects who had BMD measurements.  At analysis, the participants were classified into 5 groups, or quintiles, according to their daily calcium intake level.  The rates of first fractures in the different quintiles were compared.

The rate of fracture of any type was 17.2/1,000 patient-years in the lowest quintile of calcium intake and 14.7/1,000, 14.0/1,000, 14.1/1,000 and 14.0/1,000 patient-years for the 2^nd, 3^rd, 4^th and 5^th quintiles, respectively.  There was thus an 18% higher risk in the lowest quintile subjects than for the other quintiles.  For a first hip fracture the  rate was 4.6/1,000 patient-years in the lowest quintile of calcium intake and 3.5/1,000, 3.1/1,000, 3.4/1,000 and 3.5/1,000 patient-years for the 2^nd, 3^rd, 4^th and 5^th quintiles, respectively.  There was thus a 29% increased risk in the lowest quintile and a 0.9% to 19% increased risk for the 2^nd, 4^th and 5^th quintiles vs. the 3^rd quintile.  Low vitamin D intake further increased the risk in the lowest quintile.

The study shows an association between the lowest levels of habitual calcium intake and increased fracture risk. Above this class, further increases in intake did not further reduce the risk and appeared to be associated with increased risk of hip fracture.  Based on its results, the authors suggest that a moderate intake of calcium, combined with adequate intake of other micronutrients (e.g. vitamin), is adequate to maintain skeletal health; higher intakes may increase the risk again.

So what’s the bottom line?  The results indicate that, in the prevention of osteoporotic fractures, emphasis should be placed on people with a low intake of calcium rather than increasing the intake of those already consuming satisfactory amounts.  A satisfactory amount seems to be about 800 mg daily.  Above this level there’s little effect on women's risk for fracture or osteoporosis; if anything, there may be a very slightly increased risk of hip fracture . . .