Associations between dietary cadmium exposure and bone mineral density and risk of osteoporosis and fractures among women.

Osteoporosis and its main health outcome, fragility fractures, are large and escalating public health problems. Cadmium, a widespread food contaminant, is a proposed risk factor; still the association between estimated dietary cadmium exposure and bone mineral density (BMD) has never been assessed. Within a sub-cohort of the Swedish Mammography Cohort, we assessed dietary cadmium exposure based on a food frequency questionnaire (1997) and urinary cadmium (2004-2008) in relation to total-body BMD and risk of osteoporosis and fractures (1997-2009) among 2676 women (aged 56-69 years). In multivariable-adjusted linear regression, dietary cadmium was inversely associated with BMD at the total body and lumbar spine. After further adjustment for dietary factors important for bone health and cadmium bioavailability--calcium, magnesium, iron and fiber, the associations became more pronounced. A 32% increased risk of osteoporosis (95% CI: 2-71%) and 31% increased risk for any first incident fracture (95% CI: 2-69%) were observed comparing high dietary cadmium exposure (≥13 μg/day, median) with lower exposures (<13 μg/day). By combining high dietary with high urinary cadmium (≥0.50 μg/g creatinine), odds ratios among never-smokers were 2.65 (95% CI: 1.43-4.91) for osteoporosis and 3.05 (95% CI: 1.66-5.59) for fractures. In conclusion, even low-level cadmium exposure from food is associated with low BMD and an increased risk of osteoporosis and fractures. The partial masking of the associations by essential nutrients indicates important interplay between dietary factors and contaminants present in food. In separate analyses, dietary and urinary cadmium underestimated the association with bone effects.