All the studies that demonstrated efficacy of vitamin D to prevent fracture used at least 800 IU of cholecalciferol in largely vitamin D–deficient populations. Although ergo-calciferol is likely to be effective in preventing fractures, evidence is limited. In addition, 25(OH)D levels should be maintained above at least 32 ng/mL. Vitamin D should also be taken along with 1000 to 1200 mg per day of calcium to have maximum antifracture efficacy [25•
]. Adherence to a daily calcium and vitamin D regimen is extremely important and must be stressed to each patient.
Whether calcium absorption differs among common preparations of calcium (ie, calcium citrate or calcium carbonate) is a matter of controversy. Most forms of calcium are best absorbed in divided dosages of 500 mg or less given two to three times daily [44
]. Calcium citrate may have a slightly better absorption than calcium carbonate in patients with achlorhydria [45
]. A meta-analysis of 15 studies demonstrated an approximately 20% superior absorption of calcium citrate as compared with calcium carbonate [46
]. However, only 5 of the 15 studies included in this meta-analysis calculated calcium absorption using dual calcium isotope measurements, which are considered the gold standard. For most healthy adults, calcium carbonate or citrate supplements should adequately satisfy the daily calcium requirement. If cost is an issue, it may be more cost-effective to recommend calcium carbonate as the primary form of calcium supplementation [47
Calcium absorption does not seem to differ among different food sources such as milk, yogurt, or cheese [48
]. Dairy products contain 200 to 300 mg of calcium per serving (1 cup of milk, three quarters of a cup of yogurt, 1.25-inch cube of cheese). Absorption of calcium from cow's milk does not differ from soy milk, an increasingly popular drink, when the latter is fortified with calcium carbonate.
Cholecalciferol has been reported to be more effective in raising 25(OH)D levels compared to ergocalciferol when given in supraphysiologic dosages [49
]. Of importance, with advancing age, vitamin D production in the skin declines, making elderly populations more dependent on dietary vitamin D. For the average older person, higher dietary intake of vitamin D may be required to achieve optimal serum levels of 25(OH)D. Most dietary sources of vitamin D do not contain sufficient amounts of vitamin D to satisfy daily requirements. Foods thought to contain high amounts of vitamin D3
include fortified milk and oily fish such as salmon, mackerel, and blue fish [1••
Additional recommendations for intake in the rheumatology patient
Several rheumatologic diseases, including RA and SLE, are independent risk factors for fracture development. Glucocorticoids, which are frequently employed in the treatment of these diseases, have an additive effect on fracture risk. Vitamin D and calcium play pivotal roles in the prevention of fractures [25•
], and higher vitamin D intake may be associated with a decreased incidence of RA [32
]. The prevalence of vitamin D deficiency is as high as 67% in SLE patients [50
]. In these patients, renal disease, photosensitivity, and African American race are strong predictors of low 25(OH)D levels (< 10 ng/mL) [50
We recommend that all patients with autoimmune diseases such as SLE or RA as well as those with malabsorption (eg, Crohn's disease or ulcerative colitis) be screened for vitamin D deficiency. If insufficient (< 32 ng/mL), 50,000 IU ergocalciferol once or twice a week should be prescribed for up to 3 months. A follow-up 25(OH)D level should be determined to ensure that optimal 25(OH)D levels have been achieved. After correction of vitamin D insufficiency, we recommend ergocalciferol 50,000 IU once a month or 1000 IU of cholecalciferol daily to maintain optimal 25(OH)D levels. Physicians should consider checking vitamin D status annually or semiannually to ensure optimal circulating 25(OH)D levels year-round, especially in those patients with osteoporosis or risk for falls. presents our proposed algorithm to maintain optimal vitamin D status.
Figure 1 Proposed algorithm for optimal vitamin D status in patients with rheumatologic disease. 25(OH)D—25-hydroxyvitamin D. *If calcium level is elevated, evaluation for primary hyperparathyroidism may be necessary prior to repletion of vitamin D status. (more ...)
Calcium supplementation should be 1000 to 1200 mg daily in the form of dairy intake or over-the-counter pills in divided doses of 300 to 600 mg twice to three times a day [51
]. In patients who do not suffer from photosensitivity or who do not have risk of skin cancer, sun exposure of at least 10 to 15 minutes daily of the hands, face, and arms can be an alternative method to promote endogenous vitamin D production [27
Patients initiating glucocorticoid therapy are at especially high risk of fractures if these drugs are continued for more than 3 months. In animal studies, these agents inhibit vitamin D–mediated intestinal TRPV6 transcription [44
], which may reduce active intestinal calcium transport. Thus, if patients begin glucocorticoid treatment with an expected duration of more than 3 months, higher doses of calcium and vitamin D may be required.