More recent research on calcium and vitamin D
There are three recent studies that have information about calcium and vitamin D that might be of interest to those of us with osteoporosis that I want to discuss.
Glucocorticoid-induced osteoporosis (GIO). When high dose corticosteroids are used to treat the many medical problems that require this therapy, there is a rapid loss of bone mineral density (BMD) that follows. Some studies have apparently shown that vitamin D can reduce bone loss and fracture risk after this loss of BMD. There have been few, if any, comparisons between the effectiveness of vitamin D and the bisphosphonates, reduce BMD loss, however. This study by Sambrook PN and others compared the effectiveness of vitamin D in two forms to alendronate, which has definitely been shown effective in treating GIO. All participants also took 600 mg calcium daily. See PMID: 12733733 for details of the study. After two years there was almost 6% gain in spinal BMD in the alendronate (Fosamax) group, while both the ergocalciferol and the calcitriol groups has slightly less that 1% loss in spinal BMD. However, there was a nonsignificant loss of 3.2% and 2.2% of femoral neck BMD in the ergocalciferol and calcitriol groups, respectively, compared to the 0.9% gain of BMD in the alendronate group. The findings are interesting from several points. 1) Neither form of vitamin D is more effective, while both forms appear to be able to at least slow the loss of spinal BMD, and probably slow that loss in the femoral neck, too. The study didn't have untreated controls, so it is unknown exactly how much BMD they would have lost without any therapy. 2) Alendronate was effective at preventing loss of BMD in the spine and femoral neck, where both areas had actual increases in BMD over the two-year study. 3) Although at first glance it might appear to be alright to use either the vitamin D regimen or alendronate to combat the effects of glucocorticoids on BMD, the loss of femoral neck BMD in the vitamin D-treated groups would appear to tip the scale strongly in the favor of Alendronate. This is particularly true since treatment with the glucocorticoids is a life-time process. After several years of therapy while taking only vitamin D and calcium, there could be very significant loss of BMD, with concomittant increased fracture risk of the femoral neck. For all people on high-dose corticosteroids, routine bone density testing seems warranted to assure that BMD is staying within expected levels.
Vitamin D and secondary hyperparathyroidism. Parathyroid hormone mobilizes calcium from any place it can get it, including the gut and the bones. If vitamin D levels drop to a certain point (below which the active transport of calcium is reduced too far), hyperparathyroidism can develop as the body's method of trying to raise serum calcium levels. Thus, the combination of chronically low calcium levels ,along with reduced vitamin D levels, can lead to secondary hyperparathyroidism. This study by Gomez-Alonso C and others looked at 164 women and 162 men, all aged 54 years or older, to compare serum vitamin D levels to hyperparathyroidism incidence. See PMID: 12753264. [NOTE: To convert the various vitamin D lab results remember 1 ng/mL = 2.5 nmol/L]. If serum vitamin D was less than 10 ng/mL, 33% of subjects had hyperparathyroidism. If it was 10-18 ng/mL, then hyperparathyroidism rate was 16%, and if it was greater than 18 ng/Ml the rate was 12%. Interestingly, if 25-hydroxyvitamin D levels were greater than 40 ng/mL, there was no hyperparathyroidism. Note how these findings corroborate the Heaney and Weaver article covered in a recent Update. They actually recommend at least 80 nmol/L as an ideal minimal vitamin D level in order to help maintain optimum BMD. So, the 40 ng/mL reading would translate to 100 nmol/L, meaning these people were above Heaney and Weaver's minimal recommended level--and none had hyperparathyroidism--to confirm that level as a safe one. Bottom line: Know your serum vitamin D level, and maintain it within the normal range to help maintain ideal BMD and prevent secondary hyperparathyroidism.
Vitamin D and bone fractures. See this study by Trivedi DP and others at bmj.com because it has interesting results and because I hope you will read the email comments on the article to get some insights into the importance of looking beyond the obvious results the authors report. Also, if you will follow the discussions in the Rapid Response below the article, you will learn a lot about the chemistry of vitamin D, which is quite complex, and probably not completely understood at this time. The study reports that quarterly injections of 100,000 IU of vitamin D may reduce fractures in individuals older than 65 years. Once again, note how this study appears to corroborate the Heaney and Weaver study in the recent Update suggesting higher vitamin D intakes are needed in older individuals. One critical commentary was that, although this dosing method appears safe for most people, there are some people that it would probably kill. So, don't consider this unless you have seen your physician and gotten medical clearance. If you start this type regimen, be sure you follow your serum vitamin D levels closely to be sure they stay within normal limits.