Calcium supplements: anion effects

The effects on bone remodeling of two anions commonly associated with calcium in the food and supplement chain (carbonate and phosphate) were evaluated in a pilot study in eight normal premenopausal women. Each woman was studied twice under full metabolic balance controls, once before starting treatment and then a second time after 4 months of treatment with either sodium bicarbonate in a dose providing 3240 mg carbonate daily or a mixture of sodium and potassium phosphates, providing 1144 mg additional phosphorus daily. Intakes of calcium and protein remained approximately constant between studies. Remodeling was measured by paired studies of both whole body calcium kinetics and trans-ilial bone biopsies. The extra phosphate was almost completely absorbed and produced the expected decline in urine calcium. Both anions were associated with slight decreases in intestinal calcium absorption efficiency; however neither anion altered bone remodeling as measured either by radiocalcium kinetics or by histomorphometry. Since the anion doses we used were larger than the average woman is likely to receive from either food or supplement sources, we conclude that neither anion alters bone remodeling in humans to a clinically significant degree. Additionally these findings underscore the essential safety of increased phosphorus intakes and have relevance to the use of phosphate as a remodeling activator in the ADFR (coherence therapy) approach to treatment of osteoporosis.