Vitamin D insufficiency prior to bariatric surgery: risk factors and a pilot treatment study

Abstract

Summary Objective To assess vitamin D status and the influences of race, sun exposure and dietary vitamin D intake on vitamin D levels, and to evaluate two vitamin D repletion regimens in extremely obese patients awaiting bariatric surgery. Methods A cross-sectional analysis of dietary vitamin D, sun exposure, PTH [intact (iPTH) and PTH(1-84)] and 25-hydroxyvitamin D (25OHD; differentiated 25OHD2 and 25OHD3) in 56 obese [body mass index (BMI) > 35 kg/m2] men and women (age 20–64 years). In a pilot clinical trial, 27 subjects with 25OHD levels < 62 nmol/l were randomized to receive ergocalciferol or cholecalciferol for 8 weeks. Results Serum 25OHD was low (mean 45 ± 22 nmol/l) and was inversely associated with BMI (r = − 0.36, P < 0.01). Each BMI increase of 1 kg/m2 was associated with a 1.3 nmol/l decrease in 25OHD (P < 0.01). BMI, sun exposure, African American race and PTH predicted 40% of the variance in 25OHD (P < 0.0001). Serum 25OHD significantly increased at 4 and 8 weeks in both treatment groups (P < 0.001), whereas PTH(1-84) declined significantly in subjects treated with cholecalciferol (P < 0.007) and tended to decrease following ergocalciferol (P < 0.09). Conclusions In severely obese individuals, those who are African American, have higher BMI and limited sunlight exposure are at greatest risk for vitamin D insufficiency. These demographic factors can help to identify at-risk patients who require vitamin D repletion prior to bariatric surgery. Commonly prescribed doses of ergocalciferol and cholecalciferol are effective in raising 25OHD. Further investigation is needed to evaluate whether these regimens have differential effects on PTH, and to determine the optimal regimen for vitamin D repletion in the extremely obese patient.

The link between obesity and low circulating 25-hydroxyvitamin D concentrations: considerations and implications

“…The observation that obesity is associated with below-normal serum 25-hydroxyvitamin D concentrations and/or overt deficiency is not new; however, as obesity prevalence has grown, so have the number of reports in the literature regarding this phenomenon. [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] Some of the most recent information about low vitamin D status and obesity comes from studies in bariatric surgery patients, reporting low preoperative circulating levels of 25-hydroxyvitamin D. [21][22][23][24][25][26][27][33][34][35][36][37][38] In fact, a recent systematic review of 14 studies with about 1500 patients undergoing bariatric surgical procedures confirmed that obese individuals have serum 25-hydroxyvitamin D levels below 80 nmol l À1 preoperatively. 39 Other investigators have reported that body mass index (BMI) 25,26,[40][41][42][43][44][45][46] and body fat 20,45,…”

“…Even with very high-dose supplementation, it can be challenging to achieve normal vitamin D concentrations in bariatric surgery patients. Stein et al 26 treated patients who had serum 25-hydroxyvitamin D concentrations below 62 nmol l À1 (25 ng ml À1 ) with either 50 000 IU ergocalciferol or 8000 IU cholecalciferol weekly for 8 weeks. On average, serum 25-hydroxyvitamin D concentrations increased from 38 to 59 nmol l À1 in the cholecalciferol group, and from 34 to 78 nmol l À1 in the ergocalciferol group, with 480% compliance reported across the two treatments.…”

“…25,26,107 In a study designed to evaluate the optimal post-surgical vitamin D treatment dose, Goldner et al 35 randomized individuals after RYGB to three doses of cholecalciferol: 800, 2000 and 5000 IU per day. They found that all groups were vitamin D-inadequate (defined as serum 25-hydroxyvitamin D o30 ng ml À1 or 75 nmol l À1 ) at baseline, and that after 12 months, only 44, 78 and 70% of the individuals in the groups assigned to receive 800, 2000 and 5000 IU day À1 intake, respectively, were able to reach adequate vitamin D concentrations.…”

Bariatric surgery and bone disease: from clinical perspective to molecular insights

“…52 There is also recent and growing evidence that vitamin D has direct effects on bone cells through its interaction with specific vitamin D receptors. [53][54][55][56][57] These actions are not completely characterized but appear to include anabolic effects on osteoblast differentiation, proliferation and mineralization, as well as stimulatory effects on osteoclast precursors to enhance cellular adhesion. Taken together, these effects act to significantly increase bone turnover as measured by such markers as serum osteocalcin and bone-specific alkaline phosphatase and urinary N-telopeptide of type I collagen.…”

Expression of vitamin D-metabolizing enzymes in human adipose tissue—the effect of obesity and diet-induced weight loss

“…Low levels of circulating 25-hydroxy-vitamin D (25OHD) are associated with increased fat mass and body mass index, [1][2][3][4][5] but the underlying mechanism for this association is not fully elucidated. 6 Vitamin D (VD) is stored in adipose tissue (AT), and release of VD from AT is proposed to serve as an endogenous source of VD during the winter, when cutaneous production is low or absent in several parts of the world.…”