Background: Vitamin D supplementation is recommended to maintain bone health in the general population and in particular in patients with chronic kidney disease (CKD). While the nutritional status of vitamin D is assessed by circulating levels of 25 (OH) D3, it is not routinely measured to ensure the adequacy of vitamin D supplementation. Current recommendations require the maintenance of serum levels of 25 (OH) D3 > or = 70 nmol/L. The objective of this study is to assess the effect of routine vitamin supplements on the serum levels of 25 (OH) D3 in the general population and among persons with CKD.
Method: Using data from the third National Health and Nutrition Examination Survey (NHANES III) we assessed the adequacy of routine vitamin supplementation by assessing serum levels of 25 (OH) D3 among 15,390 adult participants, both with and without CKD.
Results: In the general population the participants with vitamin supplements had higher serum level of 25 (OH) D3 (79.47 vs 74.38 nmol/L) and a lower prevalence of vitamin D deficiency (39% vs 48%) than participants not taking any supplements. In the CKD subgroup, the prevalence of vitamin D deficiency was lower with supplements (49%), while greater without supplements (59%). Vitamin D deficiency was higher among women, elderly, and minorities as previously reported. In an adjusted regression model the odds of severe vitamin D deficiency (<25 nmol/L) was 1.43 (P=.0032) among CKD patients, with a trend toward higher rates among patients not taking vitamin supplements (odds ratio 1.47, P=.0557).
Conclusion: Vitamin supplementation is associated with a lower prevalence of vitamin D deficiency and higher serum levels of 25 (OH) D3. However, the current dose of vitamin D in routine vitamin supplements is still insufficient to maintain adequate serum 25 (OH) D3 levels in a substantial portion of both the general and CKD populations. We must re-asses the dose of vitamin D in routine vitamin supplements in the United States.