Influence of dietary sodium intake on urinary calcium excretion in selected Irish individuals.

The relationship between dietary sodium intake (as assessed by the 24-h urinary excretion of sodium) and urinary calcium excretion was examined in a selected group of free-living Irish individuals (n = 94), under conditions in which the completeness of urine collections was assessed. Results indicated that there was a significant positive correlation between 24-h urinary sodium and calcium excretion for males (r = 0.56, P less than 0.001) and females (r = 0.35, P less than 0.01). In addition, linear regression analysis indicated that mean 24-h urinary calcium excretion increased by 39 mg and 26 mg for a 1 g increment in sodium intake for males and females, respectively. The relationship between dietary sodium intake and urinary calcium excretion was also examined in 12 healthy young adults under controlled dietary conditions. Urinary sodium and calcium excretion values over 24 h were positively correlated for males (r = 0.44, P less than 0.05) and females (r = 0.80, P less than 0.001). However, the relationship was only statistically significant for 5 of the 12 subjects when the data were analysed on an individual basis. Results of this study suggest that salt intake may be an important determinant of urinary calcium loss in certain individuals and, as such, may be a risk factor in the development of osteoporosis. However, further studies are required to establish whether low salt intakes have a beneficial effect on calcium balance in free-living individuals.