Potassium causes calcium retention in healthy adults.

The administration of 60 mmol/d of KHCO3 to healthy adults reduced urinary calcium excretion by 0.9 mmol/d and caused calcium balance to become equivalently more positive. Other studies showed that 90 mmol/d of KHCO3 reduced both daily and fasting urinary calcium excretion rates, whereas deprivation of either KCl or KHCO3, using synthetic diets, was accompanied by increased daily and fasting urinary calcium excretion rates. A significant inverse relationship between the changes in urinary calcium and the changes in urinary potassium was observed: delta urinary Ca (mmol/d) = 0.29-0.015 delta urinary K (mmol/d); r = -0.65. Correlative evaluation of additional data suggested that the fall in urinary calcium during potassium administration may be related to the natriuretic effects of potassium, resulting in ECF-volume contraction or to potassium-induced phosphate retention and suppression of calcitriol synthesis, or to both mechanisms.