An important follow-up study that reaffirms calcium citrate's superior bioavailability when compared to calcium carbonate also provides new evidence of calcium citrate's role in protecting against bone loss.
A study published in the November issue of The Journal of Clinical Pharmacology used three measures to determine calcium bioavailability. This latest study compared the single-dose bioavailability and effects on hormones that regulate bone building of commercial calcium citrate and calcium carbonate supplements in postmenopausal women.
The researchers found that the tablet formulation of calcium citrate was more bioavailable than calcium carbonate, even when given with a meal. Several studies have established that calcium citrate is more bioavailable than calcium carbonate on an empty stomach, but some experts have previously suggested that the two forms of calcium are equally bioavailable when given with a meal.
Calcium citrate also produced greater suppression of a hormone called parathyroid hormone (PTH), providing evidence that calcium citrate was better absorbed. Parathyroid suppression is critical in maintaining bone because PTH is responsible for age-related bone loss. When the body senses a deficit in calcium, it responds to the challenge by increasing PTH levels and leaching calcium from the bones.
Mission Pharmacal funded the study. The company manufactures Citrical, a calcium citrate supplement.
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