Hypovitaminosis D in bariatric surgery: A systematic review of observational studies

Abstract

Background Obesity is a public health problem that carries global and substantial social and economic burden. Relative to non-surgical interventions, bariatric surgery has the most substantial and lasting impact on weight loss. However, it leads to a number of nutritional deficiencies requiring long term supplementation. Objectives The aims of this paper are to review 25-hydroxyvitamin D [25(OH)D] status pre and post - bariatric surgery, describe the dose response of vitamin D supplementation, and assess the effect of the surgical procedure on 25(OH)D level following supplementation. Methods We searched Medline, PubMed, the Cochrane Library and EMBASE, for relevant observational studies published in English, from 2000–April 2015. The identified references were reviewed, in duplicate and independently, by two reviewers. Results We identified 51 eligible observational studies assessing 25(OH)D status pre and/or post bariatric surgery. Mean pre-surgery 25(OH)D level was below 30 ng/ml in 29 studies and 17 of these studies showed mean 25(OH)D levels ≤ 20 ng/ml. Mean 25(OH)D levels remained below 30 ng/ml following bariatric surgery despite various vitamin D replacement regimens, with only few exceptions. The increase in postoperative 25(OH)D levels tended to parallel increments in vitamin D supplementation dose but varied widely across studies. An increase in 25(OH)D level by 9–13 ng/ml was achieved when vitamin D deficiency was corrected using vitamin D replacement doses of 1,100–7,100 IU/day, in addition to the usual maintenance equivalent daily dose of 400 – 2,000 IU (total equivalent daily dose 1,500–9,150 IU). There was no difference in mean 25(OH)D level following supplementation between malabsorptive/ combination procedures and restrictive procedures. Conclusion Hypovitaminosisis D persists in obese patients undergoing bariatric surgery, despite various vitamin D supplementation regimens. Further research is needed to determine the optimal vitamin D dose to reach desirable 25(OH)D levels in this population, and to demonstrate whether this dose varies according to the surgical procedure.

Hypocalcemia and osteomalacia after bariatric surgery

“…In a study from Sweden, 65% of patients had serum 25(OH) vitamin D levels less than 20 ng/dL and 69% had elevated PTH levels after a median time of 11±2.8 years postsurgery (4). Similar results have been found in other studies despite replacement of vitamin D and calcium (12). As a result lifelong calcium and vitamin D supplements are mandatory for these patients.…”

Vitamin D and intestinal calcium transport after bariatric surgery

“…Indeed, in studies of obese individuals preparing for bariatric surgery, mean preoperative 25(OH)D levels are consistently below 30 ng/mL and often below 20 ng/mL [72]. After RYGB, prevalence of vitamin D insufficiency or deficiency remains high [65,72], although reported prevalence varies substantially due to heterogeneity in approach to postoperative supplementation.…”

“…After RYGB, prevalence of vitamin D insufficiency or deficiency remains high [65,72], although reported prevalence varies substantially due to heterogeneity in approach to postoperative supplementation. Even at a given supplement dose, response to supplementation is highly variable after RYGB [65,72], with some individuals achieving 25(OH)D levels above 30 ng/mL on just 400 IU daily while others require 50,000 IU daily or more.…”

“…After RYGB, prevalence of vitamin D insufficiency or deficiency remains high [65,72], although reported prevalence varies substantially due to heterogeneity in approach to postoperative supplementation. Even at a given supplement dose, response to supplementation is highly variable after RYGB [65,72], with some individuals achieving 25(OH)D levels above 30 ng/mL on just 400 IU daily while others require 50,000 IU daily or more. As a result, professional organizations recommend repletion of low 25(OH)D levels preoperatively and routine vitamin D supplementation postoperatively, then surveillance of 25(OH)D levels with adjustment of supplement dose as needed [73–75].…”

Guidelines on vitamin D replacement in bariatric surgery: Identification and systematic appraisal

“…In particular, hypovitaminosis D remains a major problem, not only pre-operatively but also post operatively, regardless of the type of the procedure and the supplementation dose [5, 6]. In a recent systematic review of 51 observational studies assessing 25(OH)D status in obese patients undergoing bariatric surgery (follow up range: 3 months to 11 years post-operatively), mean 25-hydroxyvitamin D (25(OH)D) level was less than 30 ng/ml, before and after bariatric surgery, despite various vitamin D supplementation regimens [7]. Furthermore, 25(OH)D level was less than 20 ng/ml in half of the studies that were identified [7].…”