Calcium intakes among Australian women: Geelong Osteoporosis Study

Background: Dietary calcium deficiency may be a risk factor for osteoporosis. Aims: To estimate habitual calcium intakes and prevalence of calcium supplementation among free-living Australian women and validate a calcium-specific food-frequency questionnaire. Methods: Calcium intakes for 1045 randomly selected women (20-92 years) were estimated by questionnaire which was tested against estimates from four day weighed records kept by 32 randomly selected women. Results: The mean difference between calcium estimates was not statistically significantly different from zero (mean difference=121 mg; standard deviation of differences=357 mg; p>0.05). There was moderate agreement (weighted kappa=0.4:) between methods in ranking subjects into tertiles of calcium intake. Mean dietary calcium intakes were 615 mg/day for 20-54 years, 646 mg/day for 55-92 years and 782 mg/day for lactating women. Seventy-six per cent of women aged 20-54 years, 87% of older and 82% of lactating women had intakes below the recommended dietary intake (RDI). There was no association detected between calcium intake and age. Dairy foods provided 79.0% of dietary calcium intake. Calcium supplements were used by 6.6% and multivitamins by a further 4.3% of women. Supplementation was independent of dietary calcium intake and more likely used by postmenopausal women. Conclusions: Our results suggest that 76% of women consume less than the RDI even when supplemental calcium is included. Furthermore, 14% have less than the minimal requirement of 300 mg/day and would, therefore, be in negative calcium balance and at risk of bone loss. Despite advertising campaigns promoting better nutrition and increased awareness of osteoporosis, many women are failing to achieve an adequate calcium intake.