Calcium and Vitamin D are vitamins that we have been told will prevent osteoporosis when we are older. However, an "interesting draft recommendation statement" recently made headlines when the U.S. Preventative Task Force (USPSTF) recommended that "evidence is lacking regarding the benefit of daily supplementation with >400 IU of vitamin D3 and 1,000 mg of calcium for the primary prevention of osteoporotic fractures, and the balance of benefits and harms cannot be determined. The USPSTF concludes with moderate certainty that daily supplementation with ≤400 IU of vitamin D3 and 1,000 mg of calcium carbonate has no net benefit for the primary prevention of osteoporotic fractures." They based this recommendation due to the lack of studies showing the benefits of calcium supplementation in healthy post-menopausal women in preventing osteoporotic fractures. There were, however, "adequate evidence that supplementation with ≤400 IU of vitamin D3 and 1,000 mg of calcium carbonate increases the incidence of renal stones. The USPSTF assessed the magnitude of this harm as small."
With this "draft recommendation statement," the USPSTF could not recommend 1,000mg calcium and ≤400 IU of vitamin D supplementation in healthy post-menopausal women due to the lack of evidence showing a benefit in preventing fractures in comparison to the "adequate evidence" that supplementation can increase the incidence of renal (kidney) stones. This is a "draft recommendation statement" and not a final recommendation and is available for public comment until July 10, 2012.
I think many people are applying this recommendation to groups other than post-menopausal women. As a pregnant and soon-to-be lactating woman, it is still recommended that I take 1,000mg of calcium and 600 IU of vitamin D daily. All 1,000mg of calcium should not be taken at one time. "The percentage of calcium absorbed depends on the total amount of elemental calcium consumed at one time; as the amount increases, the percentage absorption decreases. Absorption is highest in doses ≤500 mg . So, for example, one who takes 1,000 mg/day of calcium from supplements might split the dose and take 500 mg at two separate times during the day." Vitamin D supplementation is needed along with calcium because "Vitamin D promotes calcium absorption in the gut and maintains adequate serum calcium and phosphate concentrations to enable normal mineralization of bone and to prevent hypocalcemic tetany. It is also needed for bone growth and bone remodeling by osteoblasts and osteoclasts. Together with calcium, vitamin D also helps protect older adults from osteoporosis."
Unless new information becomes available regarding pregnant and lactating women, I will continue to take my calcium supplements and/or eat my calcium rich foods (like broccoli). I think maintaining an adequate intake of calcium and vitamin D now will prevent the development of osteoporosis in the future.