The relationship of sodium intake to calcium and sodium excretion and bone mineral density of the hip in postmenopausal African-American and Caucasian women

During the past several decades in the United States, there has been a shift in dietary habits, with an increased consumption of processed foods that are high in sodium. It is known that calcium and sodium metabolism are linked and that higher sodium intakes may increase calcium excretion. Epidemiological studies in patients with idiopathic hypercalciuria suggest that hypercalciuria is linked to low bone mass. However, the relationship of sodium intake to bone mineral density (BMD) is controversial in Caucasians and has not been explored in African-Americans. To determine the consequences of sodium intake on bone in African-American and Caucasian postmenopausal women, sodium and calcium excretion and BMD of the total hip were measured in 50 Caucasian and 39 African-American postmenopausal women. After adjustment for race and urine volume, sodium excretion was a significant predictor of calcium excretion (P < 0.01). This relationship was modulated by calcium intake (P < 0.01), but not by race (P = 0.63). There was no significant effect of sodium excretion (P = 0.42) or calcium excretion (P = 0.90) on BMD of the total hip after adjusting for race and urine volume. Sodium excretion is a significant predictor of calcium excretion in both postmenopausal African-American and Caucasian women. The relationship between sodium and calcium excretion is modulated by calcium intake, and the relationship is strongest at low calcium intakes (less than or equal to 1000 mg/day). However, sodium excretion in the range of 53.75-283.33 mmole/g/total volume (mmole/g/TV) is not a significant predictor of total hip BMD in elderly African-American and Caucasian postmenopausal women.