NEW YORK (Reuters Health) Jun 15 – Phosphate and carbonate salts of calcium are equally effective in supporting bone building in women with osteoporosis, according to findings published online in the May 19th American Journal of Clinical Nutrition.

“They’re equally good objectively, but if one seems to disagree with a particular patient (whether that is real or imagined), then one can switch to the other with full confidence,” Dr. Robert P. Heaney from Creighton University, Omaha, Nebraska, told Reuters Health by email. “A supplement that someone won’t take regularly is, of course, not a good supplement for that person.”

Dr. Heaney and colleagues tested the hypothesis that a calcium-phosphate supplement would better support bone gain in osteoporotic patients than would calcium carbonate in a study that focused specifically on women with phosphorus intakes below the median for their age.

In their randomized, single-blind study, each participant received 1800 mg calcium daily as either the carbonate (106 women) or the triphosphate salt (105 women), as well as 20 micrograms teriparatide daily by subcutaneous injection and 1000 IU vitamin D3 daily by mouth.

At 3, 6, and 12 months, bone mineral density (BMD) increased at the hip and at the spine, but there were no significant differences between the two treatment groups.

Serum calcium concentrations didn’t change in either group, but urine calcium concentrations increased by 41% in the carbonate group and by 64% in the phosphate group. The difference between the groups wasn’t statistically significant.

Serum phosphorus concentrations rose by 8% in the carbonate group and by 5% in the phosphate group, small increases that did not differ significantly between the groups.

Serum creatinine increased by 6.25% in the carbonate group but did not change in the phosphate group.

Bone resorption biomarkers increased significantly across 12 months of treatment in both groups, but the increase did not differ between the treatments.

There were no serious adverse events attributable to treatment, no new fractures, and no preponderance of adverse events in either group.

Which formulation should doctors recommend?

According to Dr Heaney, “The best calcium source is neither of these two. It’s dairy – not because of any difference in the calcium itself (or its absorbability), but because bone health requires the full suite of nutrients – Ca, P , Vitamin D, K, Mg, and perhaps most important of all, high quality protein. (Recall: bone is 50% protein by volume.)”

“Supplements should be just what their name says: they should supplement an otherwise good diet,” Dr. Heaney concluded. “They can’t substitute for a good diet.”

The study was supported by Eli Lilly, who supplied the teriparatide and injection pens, and Inverness Inc who supplied the tricalcium phosphate and calcium carbonate tablets.