Vitamin D3 Loading Is Superior to Conventional Supplementation After Weight Loss Surgery in Vitamin D-Deficient Morbidly Obese Patients: a Double-Blind Randomized Placebo-Controlled Trial

Oral vitamin D supplementation for adults with obesity undergoing bariatric surgery

BACKGROUND

Vitamin D deficiency following bariatric surgery is common and is expected to be associated with a deleterious impact on the skeleton. However, the benefits of vitamin D supplementation and the optimal dose in this population is currently unknown. The available guidelines on the topic are derived from experts' opinions, and are not evidence based.

OBJECTIVES

To compare the effects of different doses of vitamin D supplementation (low dose (less than 600 international units (IU)/day), moderate dose (600 IU/day to 3500 IU/day), high dose (greater than 3500 IU/day)) to each other or to placebo in adults living with obesity undergoing bariatric surgery.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, LILACS, two trial registries, and the reference lists of systematic reviews, articles, and health technology assessment reports without language restrictions. The last search of all databases was 27 June 2023, except Embase, which we searched on 14 August 2015.

SELECTION CRITERIA

We included randomised controlled trials or controlled clinical trials on vitamin D supplementation comparing different doses or comparing vitamin D to placebo in people undergoing bariatric surgery.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Primary outcomes were fractures and adverse events. Secondary outcomes were vitamin D status, all-cause mortality, bone mineral change, secondary hyperparathyroidism, health-related quality of life, and muscle strength. We used GRADE to assess the certainty of the evidence for each outcome in each comparison.

MAIN RESULTS

We identified five trials with 314 participants. We included three trials in the quantitative analysis. Moderate-dose vitamin D compared to placebo One trial compared moderate-dose vitamin D (3200 IU/day) to placebo. Moderate-dose vitamin D, compared to placebo, may improve vitamin D status and may result in little to no difference in the achieved parathyroid hormone level (achieved 25-hydroxyvitamin D level: mean difference (MD) 13.60 ng/mL, 95% confidence interval (CI) 7.94 to 19.26; achieved parathyroid hormone level: -6.60 pg/mL, 95% CI -17.12 to 3.92; 1 study, 79 participants; low-certainty evidence). The trial reported no adverse events in the moderate-dose vitamin D arm, but did not provide any information on adverse events in the placebo arm. There were no data on fractures, all-cause mortality, bone density change, health-related quality of life, and muscle strength. High-dose vitamin D compared to moderate-dose vitamin D Two trials in Roux-en-Y gastric bypass compared moderate-dose (equivalent dose 800 IU/day to 2000 IU/day) to high-dose (equivalent dose 5000 IU/day to 7943 IU/day) vitamin D. The evidence of high-dose vitamin D on adverse events is very uncertain (risk ratio (RR) 5.18, 95% CI 0.23 to 116.56; 2 studies, 81 participants; very low-certainty evidence). High-dose vitamin D may increase 25-hydroxyvitamin D levels compared to a moderate dose at 12 months, but the evidence is very uncertain (MD 15.55 ng/mL, 95% CI 3.50 to 27.61; I2 = 62%; 2 studies, 73 participants; very low-certainty evidence). High-dose vitamin D may have little to no effect on parathyroid hormone levels compared to a moderate dose at 12 months, but the evidence is very uncertain (MD 2.15 pg/mL, 95% CI -21.31 to 17.01; I2 = 0%; 2 studies, 72 participants; very low-certainty evidence). High-dose vitamin D may have little to no effect on mortality and bone mineral density at the lumbar spine, hip, and forearm, but the evidence is very uncertain. There were no data on fractures, health-related quality of life, or muscle strength.

AUTHORS' CONCLUSIONS

No trials reported on fractures and the evidence available on adverse events is scarce. Moderate-dose vitamin D may improve vitamin D status and may result in little to no improvement in parathyroid hormone levels compared with placebo. High-dose vitamin D supplementation (greater than 3500 IU/day) may increase 25-hydroxyvitamin D levels, and may have little to no effect on parathyroid hormone levels, compared to a moderate dose, but the evidence for both is very uncertain. The currently available limited evidence may not have a significant impact on practice. Further studies are needed to explore the impact of vitamin D supplementation on fractures, adverse events, and musculoskeletal parameters in people undergoing bariatric surgery.

A Systematic Review and Meta-Analysis of Vitamin D Status of Patients with Severe Obesity in Various Regions Worldwide

INTRODUCTION

Managing nutritional deficiencies is an essential component in the treatment of severe obesity. Vitamin D deficiency is often reported in investigations in severely obese cohorts. However, no prior study has summarized findings on this topic. Consequently, the aim of this systematic review and meta-analysis was to investigate the 25-hydroxyvitamin D [25(OH)D] status in individuals with severe obesity in different regions worldwide. We also evaluated levels of calcium, parathyroid hormone (PTH), and magnesium as secondary outcome measures.

METHODS

We searched Medline, PubMed, Scopus, the Cochrane Library, and EMBASE for relevant observational studies published in English from 2009 to October 2021. The heterogeneity index among the studies was determined using the Cochran (Q) and I2 tests. Based on the heterogeneity results, the random-effect model was applied to estimate the prevalence of vitamin D deficiency.

RESULTS

We identified 109 eligible observational studies. Overall, 59.44% of patients had vitamin D deficiency [25(OH)D <20 ng/mL], whereas 26.95% had vitamin D insufficiency [25(OH)D 20-30 ng/mL]. Moreover, the mean 25(OH)D level was 18.65 ng/mL in 96 studies. The pooled mean estimate of the serum calcium, PTH, and magnesium was 9.26 mg/dL (95% confidence interval [CI]: 9.19-9.32, I2 = 99.7%, p < 0.001), 59.24 pg/mL (95% CI: 54.98, 63.51, I2 = 99.7%, p < 0.001), and 0.91 mg/dL (95% CI: 0.84, 0.98, I2 = 100.0%, p < 0.001), respectively. The results of the subgroup analysis indicated that the mean estimates of 25(OH)D were highest in North America (21.71 ng/mL [19.69, 23.74], [I2 = 97.2%, p < 0.001]) and lowest in Southeast Asia (14.93 ng/mL [14.54, 15.33], [I2 = 0.0%, p = 0.778]).

CONCLUSION

The results obtained showed a significant prevalence of vitamin D deficiency among severely obese individuals in various geographical regions, whereas the highest and lowest mean estimates were reported for North America and Southeast Asia, respectively.

Long-Term Changes in Bone Density and Bone Metabolism After Gastric Bypass Surgery: a Retrospective Cohort Study

PURPOSE

Patients with severe obesity submitted to Roux-en-Y gastric bypass (RYGB) are at risk of developing long-term hypovitaminosis D and secondary hyperparathyroidism (SHPT) as well as osteometabolic disease. This study aimed to evaluate calcium-vitamin D-PTH axis and bone mineral density (BMD) changes from post-RYGB patients who were followed-up until a median of 5 years.

MATERIALS AND METHODS

Vitamin D deficiency was defined as 25-hydroxyvitamin D <20 ng/mL and SHPT as PTH >68 pg/mL, in patients with normal serum creatinine and calcium. BMD was estimated by dual-energy X-ray absorptiometry (DXA, g/cm²).

RESULTS

We included 127 post-RYGB patients (51±10.6 years, 87.4% self-declared White, 91.3% female, 52.8% postmenopausal). Vitamin D deficiency prevalence was the highest (41.5%) in the second year and the lowest (21.2%) in the third year (p<0.05). SHPT prevalence was 65.4% in the second year and increased to 83.7% in the sixth year (p<0.05). Patients with low BMD in lumbar, femoral neck, and total proximal femur were older and presented menopausal status more frequently than normal BMD group (p<0.05). Older age was a risk marker for altered BMD in femoral neck (OR=1.185; 95% CI 1.118-1.256) and in total proximal femur (OR=1.158; 95% CI 1.066-1.258), both after adjusting for follow-up and excess weight loss.

CONCLUSION

After 5 years, most bariatric patients presented calcium-vitamin D-PTH axis disruption, in which SHPT was more frequent than hypovitaminosis D. Older patients and menopausal women presented higher rates of low BMD, and older age was a risk marker, especially for low BMD in femoral sites.

The Effect of Vitamin D Supplementation on Serum 25-Hydroxy Vitamin D in the Patients Undergoing Bariatric Surgery: a Systematic Review and Meta-Analysis of Randomized Clinical Trials

Currently, there is no consensus on the optimal vitamin D administration in bariatric patients. The present systematic review and meta-analysis were conducted to examine the effect of vitamin D supplements on serum level of 25(OH) vitamin D in the patients undergoing bariatric surgery (BS).Random model effects were used to estimate standardized mean difference (SMD) with a 95% confidence interval (CI). Nine clinical trials were included in the meta-analysis. Vitamin D supplementation in patients undergoing BS modestly improves vitamin D status (SMD, 0.53; 95% CI, 0.28, 0.77) particularly, in the dosages above 2850 IU/day and in the patients with BMI greater than 50 kg/m². Vitamin D supplementation was associated with prevention of raising of the PTH serum concentration and without impact on serum calcium levels.

Vitamin D and Calcium Status Among Adolescents with Morbid Obesity Undergoing Bariatric Surgery

PURPOSE

Obesity is very prevalent among children and adolescents these days. Obese children are at increased risk of vitamin D and other micronutrient deficiencies. This risk is even higher in children and adolescents with morbid obesity who are candidates for bariatric surgery. Although multiple studies have studied the prevalence of vitamin D deficiency in adults undergoing bariatric surgery, studies are limited concerning adolescents in this regard. We aimed to study the prevalence of vitamin D deficiency and insufficiency and calcium status among morbidly obese children and adolescents.

MATERIALS AND METHODS

A number of 96 adolescents (20 years old and younger) with morbid obesity (BMI ≥ 99% percentile), who were candidates for bariatric surgery, were enrolled in this study (from 2016 to 2018), and their serum vitamin D and calcium levels were measured.

RESULTS

Sixty-four percent of the patients were vitamin D-deficient and 15.7% of them had insufficient levels of serum vitamin D. Only 20.2% of the children had sufficient serum vitamin D levels. Serum calcium levels were within the normal range among all of the patients. There was no significant relationship between age and sex with vitamin D levels.

CONCLUSION

Vitamin D deficiency is of very high prevalence among adolescents with morbid obesity.

Secondary Hyperparathyroidism Among Bariatric Patients: Unraveling the Prevalence of an Overlooked Foe

INTRODUCTION

Bariatric surgery (BS) is the most effective therapeutic approach to obesity. It is associated with great gastrointestinal anatomic changes, predisposing the patients to altered nutrient absorption that impacts phosphocalcium metabolism. This study aimed to clarify the prevalence of secondary hyperparathyroidism (SHPT) and its predictors in patients submitted to BS.

METHODS

Retrospective study of 1431 patients who underwent metabolic surgery between January 2010 and June 2017 and who were followed for at least 1 year. We compared the clinical and biochemical characteristics of patients with and without secondary hyperparathyroidism (considering SHPT a PTH ˃ 69 pg/mL). Two different analyses were performed: (1) paired analysis of participants before and 1 year after surgery (N = 441); (2) Cross sectional analysis of participants submitted to bariatric surgery before (N = 441), 1 year after (N = 1431) and 4 years after surgery (N = 333). Multiple logistic regression models were used to evaluate possible predictors of SHPT after BS.

RESULTS

The overall prevalence of SHPT was 24.9% before surgery, 11.2% 1 year after surgery and 21.3% 4 years after surgery. Patients submitted to LAGB had the highest prevalence of SHPT 1 year after surgery (19.4%; vs RYGB, 12.8%, vs SG, 5.3%). Four years after surgery, RYGB had the highest prevalence of SHPT (27.0%), followed by LAGB (13.2%) and SG (6.9%). Higher body mass index and age, decreased levels of vitamin D and RYGB seem to be independent predictors of SHPT 1 year after surgery. The only independent predictor of SHPT 4 years after surgery was RYGB.

CONCLUSION

The prevalence of SHPT is higher before and 4 years after BS than 1 year after surgery. This fact raises some questions about the efficacy of the implemented follow-up plans of vitamin D supplementation on the long term, mainly among patients submitted to RYGB.

Effect of one-anastomosis gastric bypass on cardiovascular risk factors in patients with vitamin D deficiency and morbid obesity: A secondary analysis

BACKGROUND AND AIMS

Bariatric patients often suffer from vitamin D (VD) deficiency, and both, morbid obesity and VD deficiency, are related to an adverse effect on cardiovascular disease (CVD) risk. Therefore, we assessed the change of known CVD risk factors and its associations during the first 12 months following one-anastomosis gastric bypass (OAGB).

METHODS AND RESULTS

In this secondary analysis, CVD risk factors, medical history and anthropometric data were assessed in fifty VD deficient (25-hydroxy-vitamin D (25(OH)D) <75 nmol/l) patients, recruited for a randomized controlled trial of VD supplementation. Based on previous results regarding bone-mass loss and the association between VD and CVD risk, the study population was divided into patients with 25(OH)D ≥50 nmol/l (adequate VD group; AVD) and into those <50 nmol/l (inadequate VD group; IVD) at 6 and 12 months (T6/12) postoperatively. In the whole cohort, substantial remission rates for hypertension (38%), diabetes (30%), and dyslipidaemia (41%) and a significant reduction in CVD risk factors were observed at T12. Changes of insulin resistance markers were associated with changes of total body fat mass (TBF%), 25(OH)D, and ferritin. Moreover, significant differences in insulin resistance markers between AVD and IVD became evident at T12.

CONCLUSION

These findings show that OAGB leads to a significant reduction in CVD risk factors and amelioration of insulin resistance markers, which might be connected to reduced TBF%, change in 25(OH)D and ferritin levels, as an indicator for subclinical inflammation, and an adequate VD status. REGISTERED AT CLINICALTRIALS.GOV: (Identifier: NCT02092376) and EudraCT (Identifier: 2013-003546-16).

Course of depressive symptomatology and its association with serum uric acid in one-anastomosis gastric bypass patients

The changes in depressive symptomatology during the first year following one-anastomosis gastric bypass (OAGB) were evaluated and its association with uric acid (sUA). Fifty patients were included in this analysis. Beck Depression Inventory (BDI) for measuring depressive symptomatology, blood samples, and anthropometric measurements were assessed before (T0), at 6 (T6), and 12 months (T12) after surgery. There was a significant reduction in BDI total score at T6 (− 5.6 (95% CI − 2.1, − 9.1) points; p = 0.001) and at T12 (− 4.3 (95% CI − 0.9, − 7.9) points; p = 0.011). BMI loss was unrelated to depressive symptomatology. Patients with moderate to severe depressive symptomatology presented lower sUA levels than patients with none or minimal to mild (p = 0.028). ROC analysis revealed that sUA levels below 5.0 at T6 and 4.5 mg/dl at T12 had a prognostic accuracy for depression severity. Furthermore, delta sUA was significantly associated with delta BMI (β = 0.473; p = 0.012) and delta waist circumference (β = 0.531; p = 0.003). These findings support an improvement in depressive symptomatology in the first year postoperatively, however, without relation to BMI loss. Patients with moderate to severe depressive symptomatology presented with lower sUA levels over time. Therefore, sUA could be useful to predict moderate to severe depressive symptomatology in patients undergoing OAGB in clinical practice.

Systematic review and meta-analysis of perioperative behavioral lifestyle and nutritional interventions in bariatric surgery: a call for better research and reporting

Bariatric surgery is considered the most effective treatment for people with morbid obesity, and certain interventions could enhance its long-term results. We searched MEDLINE, Embase, Web of Science, CENTRAL, and trial registers up to January 1, 2020. Randomized controlled trials, where behavioral lifestyle or nutritional interventions were provided perioperatively were included. Primary outcome was weight change. Two reviewers independently performed each stage of the review. Altogether 6652 references were screened. 31 studies were included for qualitative synthesis and 22 studies for quantitative synthesis. Interventions varied greatly, thus limiting possibility of synthesizing all results. Six groups of interventions were discerned, and we used standardized mean differences for synthesis. Low to very-low certainty evidence suggests that physical activity, nonvitamin nutritional interventions, vitamins, psychotherapy, and counseling but not combined interventions might bring some benefit regarding short-term postsurgery follow-ups (up to 12 mo), but the estimates varied and results were not statistically significant, except for 12 months follow-ups regarding counseling. Psychotherapy and counseling, but not vitamins and combined interventions, may provide some benefit at longer follow-ups (over 12 mo), but the certainty of evidence was low to very-low and statistically significant results were observed in comparisons including data from single studies with small sample sizes only. Included studies expressed an outcome "weight change" using 20 different measures. Misreporting of data and huge variety of outcomes do not benefit systematic analyses and may possibly lead to confusion of both researchers and readers. We suggest that authors follow a predefined set of outcomes when reporting the results of their studies. The initiative to produce "core outcome set" for clinical trials in bariatric surgery trials is currently underway.

Recommendations Based on Evidence by the Andalusian Group for Nutrition Reflection and Investigation (GARIN) for the Pre- and Postoperative Management of Patients Undergoing Obesity Surgery

In order to develop evidence-based recommendations and expert consensus for nutrition management of patients undergoing bariatric surgery and postoperative follow-up, we conducted a systematic literature search using PRISMA methodology plus critical appraisal following the SIGN and AGREE-II procedures. The results were discussed among all members of the GARIN group, and all members answered a Likert scale questionnaire to assess the degree of support for every recommendation. Patients undergoing bariatric surgery should be screened preoperatively for some micronutrient deficiencies and treated accordingly. A VLCD (Very Low-Calorie Diet) should be used for 4-8 weeks prior to surgery. Postoperatively, a liquid diet should be maintained for a month, followed by a semi-solid diet also for one month. Protein requirements (1-1.5 g/kg) should be estimated using adjusted weight. Systematic use of specific multivitamin supplements is encouraged. Calcium citrate and vitamin D supplements should be used at higher doses than are currently recommended. The use of proton-pump inhibitors should be individualised, and vitamin B12 and iron should be supplemented in case of deficit. All patients, especially pregnant women, teenagers, and elderly patients require a multidisciplinary approach and specialised follow-up. These recommendations and suggestions regarding nutrition management when undergoing bariatric surgery and postoperative follow-up have direct clinical applicability.

Cholecalciferol or Calcifediol in the Management of Vitamin D Deficiency

Vitamin D deficiency is a global health problem due to its high prevalence and its negative consequences on musculoskeletal and extra-skeletal health. In our comparative review of the two exogenous vitamin D supplementation options most used in our care setting, we found that cholecalciferol has more scientific evidence with positive results than calcifediol in musculoskeletal diseases and that it is the form of vitamin D of choice in the most accepted and internationally recognized clinical guidelines on the management of osteoporosis. Cholecalciferol, unlike calcifediol, guarantees an exact dosage in IU (International Units) of vitamin D and has pharmacokinetic properties that allow either daily or even weekly, fortnightly, or monthly administration in its equivalent doses, which can facilitate adherence to treatment. Regardless of the pattern of administration, cholecalciferol may be more likely to achieve serum levels of 25(OH)D (25-hydroxy-vitamin D) of 30-50 ng/mL, an interval considered optimal for maximum benefit at the lowest risk. In summary, the form of vitamin D of choice for exogenous supplementation should be cholecalciferol, with calcifediol reserved for patients with liver failure or severe intestinal malabsorption syndromes.

Proceedings of the 2017 ASPEN Research Workshop-Gastric Bypass: Role of the Gut

The goal of the National Institutes of Health-funded American Society for Parenteral and Enteral Nutrition 2017 research workshop (RW) "Gastric Bypass: Role of the Gut" was to focus on the exciting research evaluating gut-derived signals in modulating outcomes after bariatric surgery. Although gastric bypass surgery has undoubted positive effects, the mechanistic basis of improved outcomes cannot be solely explained by caloric restriction. Emerging data suggest that bile acid metabolic pathways, luminal contents, energy balance, gut mucosal integrity, as well as the gut microbiota are significantly modulated after bariatric surgery and may be responsible for the variable outcomes, each of which was rigorously evaluated. The RW served as a timely and novel academic meeting that brought together clinicians and researchers across the scientific spectrum, fostering a unique venue for interdisciplinary collaboration among investigators. It promoted engaging discussion and evolution of new research hypotheses and ideas, driving the development of novel ameliorative, therapeutic, and nonsurgical interventions targeting obesity and its comorbidities. Importantly, a critical evaluation of the current knowledge regarding gut-modulated signaling after bariatric surgery, potential pitfalls, and lacunae were thoroughly addressed.

Changes in Bone Mineral Density Following Weight Loss Induced by One-Anastomosis Gastric Bypass in Patients with Vitamin D Supplementation

BACKGROUND

Little is known about changes in bone mineral density (BMD) following weight loss after one-anastomosis gastric bypass (OAGB) and the role of serum vitamin D and its supplementation on bone metabolism. We evaluated BMD after OAGB as a function of vitamin D supplementation with respect to a minimum threshold of 25-hydroxy-vitamin-D [25(OH)D] concentration, which could prevent or decelerate an eventual bone loss.

METHODS

Fifty bariatric patients who participated in the randomized controlled trial were included in this analysis. BMD and anthropometric measurements by DXA and laboratory parameters were assessed before (T0), at 6 (T6), and 12 months (T12) after surgery.

RESULTS

OAGB resulted in a 36% total body weight loss with a decrease in body fat and an increase in lean body mass. A significant decrease in BMD was seen in lumbar spine by 7%, left hip 13%, and total body 1%, but not in forearm. Bone turnover markers increased significantly but with normal parathyroid hormone concentrations. Weight loss was not associated with changes in BMD. A serum 25(OH)D concentration > 50 nmol/l at T6 and T12 (adequate-vitamin-D-group; AVD) showed a significant lower bone loss, compared to the inadequate-vitamin-D-group (IVD; < 50 nmol/l). Lower bone loss in the left hip showed a strong correlation with higher 25(OH)D concentrations (r = 0.635, p = 0.003).

CONCLUSION

These findings support a dose effect of vitamin D supplementation on bone health and suggest that 25(OH)D concentrations need to be above 50 nmol/l at least during the first postoperative year to decelerate bone loss in patients undergoing OAGB.

CLINICAL TRIAL REGISTRY NUMBER AND WEBSITE

Clinicaltrials.gov (NCT02092376) at https://clinicaltrials.gov /. EudraCT (2013-003546-16) at https://eudract.ema.europa.eu /.

High dose vitamin D supplementation does not rescue bone loss following Roux-en-Y gastric bypass in female rats

Postoperative bone loss and increased fracture risk associated with Roux-en-Y gastric bypass (RYGB) have been attributed to vitamin D/calcium malabsorption and resultant secondary hyperparathyroidism (HPT). Adequate vitamin D supplementation (VDS), particularly in an older female population, reduces incidence of secondary HPT but the effect on bone loss and fracture risk remains unclear. To investigate whether VDS corrects the RYGB bone phenotype, 41 obese adult female rats were randomized to RYGB with 1000 IU (R1000) or 5000 IU (R5000) vitamin D/kg food or a sham surgical procedure with either paired (PF) or ad libitum (AL) feeding. Bone turnover markers, urinary calcium/creatinine ratio (CCR), and serum calciotropic and gut hormones were assessed throughout a 14-week postoperative period. Femurs were analyzed by micro-computed tomography (μCT), three-point bending test, and histomorphometry. 1000 IU animals had low 25‑hydroxyvitamin D (25(OH)D), high serum parathyroid hormone (PTH), and very low urine CCR levels. 5000 IU corrected the 25(OH)D and secondary HPT but did not increase urine CCR or serum levels of 1,25‑dihydroxyvitamin D (1,25(OH)D) significantly between RYGB groups. Compared to sham animals at 14 weeks, RYGB animals had significantly higher serum osteocalcin (OCN) and C-terminal telopeptide (CTX) levels. The gut hormone peptide tyrosine tyrosine hormone (PYY) was higher in the RYGB groups, and leptin was lower. μCT and biomechanical testing revealed RYGB females had decreased cortical and trabecular bone volume and weaker, stiffer bone than controls. Histomorphometry showed decreased bone volume and increased osteoid volume with increased mineral apposition rate in RYGB compared to controls. No differences in bone phenotype were identified between 1000 IU and 5000 IU groups, and osteoclast numbers were comparable across all four groups. Thus, in our model, 5000 IU VDS corrected vitamin D deficiency and secondary HPT but did not rescue RYGB mineralization rate nor the osteomalacia phenotype. Longer studies in this model are required to evaluate durability of these detrimental effects. Our findings not only underscore the importance of lifelong repletion of both calcium and vitamin D but also suggest that additional factors affect skeletal health in this population.

Differences in Serum Magnesium Levels in Diabetic and Non-Diabetic Patients Following One-Anastomosis Gastric Bypass

Patients with obesity and type 2 diabetes mellitus (T2DM) are regarded to have reduced serum magnesium (Mg) concentrations. We aimed to assess the changes in serum Mg concentrations at 12-month follow-up in patients, with and without T2DM, who underwent one anastomosis gastric bypass surgery. Overall, 50 patients (80% female, age 42.2 (12.5) years) with morbid obesity (mean baseline BMI 43.8 (4.3) kg/m2) were included in the analysis. Half of the included patients had T2DM diagnosed at baseline, and these patients showed lower serum Mg concentration (0.78 (0.07)) vs. 0.83 (0.05) mmol/L; p = 0.006), higher blood glucose levels (129.9 (41.3) vs. 87.6 (8.1) mg/dL; p < 0.001) as well as HbA1c concentrations (6.7 (1.4) vs. 5.3 (0.5)%; p < 0.001). During follow-up, BMI and glucose levels showed a decrease; however, serum Mg levels remained stable. At baseline 42% of patients were found to be Mg deficient, which was reduced to 33% at six months and to 30% at 12 months follow-up. Moreover, patients with T2DM had an odds ratio of 9.5 (95% CI = 3.0-29.7; p < 0.001) for magnesium deficiency when compared to patients without T2DM. Further research into the role of Mg and its role in T2DM and other obesity-related comorbidities are needed.

A systematic review and meta-analysis of the response of serum 25-hydroxyvitamin D concentration to vitamin D supplementation from RCTs from around the globe

BACKGROUND/OBJECTIVES

Optimal doses of vitamin D (VitD) supplement in different populations are unclear. We aim to evaluate the relationship between VitD supplementation and post-intervention serum 25-hydroxyvitamin D [25(OH)D] concentration, to provide a recommended dosage of VitD for achieving an optimal 25(OH)D concentration for different populations.

SUBJECTS/METHODS

Literature search was conducted in Embase, etc. Randomized controlled trials about VitD supplemental intakes and their effect on 25(OH)D concentration were enrolled. The effect on 25(OH)D concentration between different supplementation doses in each population group was compared by meta-analysis. Multivariate meta-regression model is utilized to establish reference intake dosage of VitD.

RESULTS

A total of 136 articles were included about children (3-17 years), adults (18-64 years), postmenopausal women, the elderly ( >64 years), pregnant, or lactating women. Overall, intervention groups obtained higher 25(OH)D concentration than controls and there was obvious dose-response effect between intake dose and 25(OH)D concentration. Baseline 25(OH)D concentration and age were significant indicators for 25(OH)D concentration. To reach sufficient 25(OH)D concentration (75 nmol/L), the recommended VitD supplemental intakes was 1340 and 2250 IU/day for children and pregnant women, 2519 and 797 IU/day for European adults aged 18-64 and 65-85 years, 729, 2026, and 1229 IU/day for adults in North America, Asia and Middle East and Africa, respectively.

CONCLUSIONS

Regional- and age-specific recommended dosages of VitD supplements for population to achieve optimal 25(OH)D concentrations have been suggested.

Association between Vitamin D Levels and Nonalcoholic Fatty Liver Disease: Potential Confounding Variables

Nonalcoholic fatty liver disease (NAFLD), historically considered to be the hepatic component of the metabolic syndrome, is a spectrum of fat-associated liver conditions, in the absence of secondary causes, that may progress to nonalcoholic steatohepatitis (NASH), fibrosis, and cirrhosis. Disease progression is closely associated with body weight or fatness, dyslipidemia, insulin resistance, oxidative stress, and inflammation. Recently, vitamin D deficiency has been linked to the pathogenesis and severity of NAFLD because of vitamin D "pleiotropic" functions, with roles in immune modulation, cell differentiation and proliferation, and regulation of inflammation. Indeed, several studies have reported an association between vitamin D and NAFLD/NASH. However, other studies have failed to find an association. Therefore, we sought to critically review the current evidence on the association between vitamin D deficiency and NAFLD/NASH, and to analyze and discuss some key variables that may interfere with this evaluation, such as host-, environment-, and heritability-related factors regulating vitamin D synthesis and metabolism; definitions of deficient or optimal vitamin D status with respect to skeletal and nonskeletal outcomes including NAFLD/NASH; methods of measuring 25(OH)D; and methods of diagnosing NAFLD as well as quantifying adiposity, the cardinal link between vitamin D deficiency and NAFLD.

Vitamin D supplementation in obesity and during weight loss: A review of randomized controlled trials

Vitamin D deficiency is common in obese individuals and during weight loss. The recommended vitamin D doses in this specific population are higher than for healthy adults. We reviewed vitamin D supplementation trials in obesity, and during medical or surgical weight loss, and report the effects on 25-hydroxyvitamin D [25(OH)D] concentrations and other relevant outcomes. We conducted a systematic search in PubMed, Medline, Embase and the Cochrane library for relevant randomized controlled trials (RCTs) of oral vitamin D supplementation for at least 3 months in obese individuals without weight loss (OB), and those on medical weight loss (MWL) (2010-2018), and following bariatric surgery (Bar S) (without time restriction). Two reviewers screened the identified citations in duplicate and independently and performed full text screening. One reviewer completed data extraction. We identified 13 RCTs in OB, 6 in MWL and 7 in Bar S. Mean baseline 25(OH)D concentrations ranged between 7 and 27 ng/ml in OB, 15-29 ng/ml in MWL and 15-24 ng/ml in Bar S. In OB (Total N 2036 participants), vitamin D doses of 1600-4000 IU/d increased mean 25(OH)D concentrations to ≥30 ng/ml. Based on three trials during MWL (Total N 359 participants), vitamin D doses of 1200-4600 IU/d for 12 months increased 25(OH)D concentration to ≥30 ng/ml. In Bar S (Total N 615 participants), doses ≥2000 IU/d were needed to reach 30 ng/ml. The change in 25(OH)D concentration was inversely proportional to the administered dose, and to BMI and baseline level with doses of 600-3000 IU/day. With these doses, the change in 25(OH)D concentration [Δ25(OH)D] per 100 IU/d was 0.5-1.2 ng/ml. Three trials assessed bone mineral density as a primary outcome, but only one of them showed a protective effect of vitamin D against bone loss at all sites post-Bar S. There was no effect of vitamin D on weight loss. Data on extra-skeletal parameters, namely glycemic and vascular indices were mostly identified in OB, and findings were inconsistent. In conclusion, Vitamin D doses ≥1600-2000 IU/d may be needed to reach a 25(OH)D concentration of 30 ng/ml in obese individuals and following bariatric surgery. The optimal concentration in this population is unknown, and whether the above doses protect against weight loss induced bone loss and fractures still needs to be confirmed. There is no clear evidence for a beneficial effect of vitamin D supplementation on cardio-metabolic parameters in obese individuals, and data on such parameters with weight loss are very scarce. Well-designed long term RCTs assessing the effect of vitamin D supplementation during weight loss on patient important outcomes are needed.

High Incidence of Secondary Hyperparathyroidism in Bariatric Patients: Comparing Different Procedures

BACKGROUND

Bariatric surgery is an effective therapy for morbid obesity but may reduce calcium absorption and significantly decrease the bone mineral density. This study examined the prevalence of secondary hyperparathyroidism (SHPT) in obese subjects during follow-up after different bariatric surgeries. We investigated predictors of SHPT.

METHODS

We enrolled 1470 obese subjects undergoing bariatric/metabolic surgery with at least 1-year follow-up, including 322 patients undergoing Roux-en-Y gastric bypass (RYGB), 695 undergoing single anastomosis (mini-) gastric bypass (SAGB), 93 undergoing laparoscopic adjustable gastric banding (LAGB), and 360 undergoing sleeve gastrectomy (SG). Five years of data were available for 215 patients. Patients were instructed to supplement their diet according to the guideline. Calcium, parathyroid hormone (PTH), and vitamin D levels were measured before surgery and at 1 and 5 years after surgery. SHPT was defined as PTH > 69 pg/mL.

RESULTS

The overall prevalence of SHPT was high, 21.0% before surgery and was not different between patients with different bariatric procedures. Pre-operative PTH correlated with age, BMI, and vitamin D levels. Multi-variate analysis confirmed that vitamin D level was the only independent predictor of SHPT before surgery. The prevalence of SHPT increased to 35.4% at 1 year after surgery and 63.3% at 5 years after surgery. SAGB had the highest prevalence of SHPT (50.6%) followed by RYGB (33.2%), LAGB (25.8%), and SG (17.8%) at 1 year after surgery. At 5 years after surgery, SAGB still had the highest prevalence of SHPT (73.6%), followed by RYGB (56.6%), LAGB (38.5%), and SG (41.7%). Serum PTH at 1 year after surgery correlated with decreased BMI and weight loss. Multi-variate analysis confirmed that age, sex, calcium level, and bypass procedure were independent predictor of SHPT after surgery.

CONCLUSIONS

The prevalence of SHPT is high in morbidly obese patients before bariatric surgery which is related to vitamin D deficiency. The prevalence of SHPT increased continually along with the time after bariatric surgery, especially in patients receiving SAGB, followed by RYGB. The supplementation of vitamin D and calcium have to be higher in bypass procedure, especially in malabsorptive procedure.

Relationships of serum 25-hydroxyvitamin D, ionized calcium and parathyroid hormone after obesity surgery

OBJECTIVE

The high prevalence of secondary hyperparathyroidism (SHPT) after obesity surgery is a concern for long-term bone health. Limited knowledge exists about optimal vitamin D and suppression of parathyroid hormone (PTH) after these procedures. The aim of this study was to investigate the prevalence of SHPT and its relation to vitamin D status.

DESIGN

A cross-sectional study at Oslo University Hospital, Norway.

PATIENTS

A total of 502 consecutive patients, age 22-64 years, attending 2-year follow-up after Roux-en-Y gastric bypass.

MEASUREMENTS

A serum intact PTH >7.0 pmol/L in the absence of elevated serum ionized calcium (iCa) was considered as SHPT. Vitamin D status was defined by serum concentrations of 25-hydroxyvitamin D (S-25(OH)D).

RESULTS

Altogether, 171 patients (34%) had SHPT. The prevalence of SHPT varied across the range of S-25(OH)D (P < 0.001), being highest (71%) with S-25(OH)D < 25 nmol/L. Compared with S-25(OH)D < 50 nmol/L, the prevalence of SHPT was lower with S-25(OH)D ≥ 50 nmol/L (29.0%; RR = 0.64 (95%-CI:0.50-0.81)) and S-25(OH)D ≥ 75 nmol/L (27.7%; RR = 0.61 (95%-CI:0.44-0.84)). S-25(OH)D ≥ 100 nmol/L was associated with the lowest PTH and the lowest prevalence of SHPT (16.0%; RR = 0.35 (95%-CI:0.14-0.88) compared with S-25(OH)D < 50 nmol/L) and the most normal calcium distribution. These associations were most pronounced with iCa in the lower range. A synergistic association was found for S-25(OH)D and iCa on SHPT.

CONCLUSIONS

Vitamin D deficient patients had the highest prevalence of SHPT 2 years after gastric bypass. PTH and the prevalence of SHPT were notably lower with S-25(OH)D ≥ 100 nmol/L, compared with lower target levels.

Vitamin D Metabolism in Bariatric Surgery

Hypovitaminosis D is common in obese patients and persists after roux-en-Y gastric bypass and sleeve gastrectomy. Several societies recommend screening for vitamin D deficiency before bariatric surgery, and replacement doses of 3000 IU/d and up to 50,000 IU 1 to 3 times per week, in case of deficiency, with periodic monitoring. These regimens are mostly based on expert opinion. Large trials are needed to assess the vitamin D dose response, by type of bariatric surgery, and evaluate the effect on surrogate markers of skeletal outcomes. Such data are essential to derive desirable vitamin D levels in this population.

Vitamin D Supplementation and Non-Alcoholic Fatty Liver Disease: Present and Future

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic hepatic disease throughout the Western world and is recognized as the main cause of cryptogenic cirrhosis; however, the identification of an effective therapy for NAFLD is still a major challenge. Vitamin D deficiency is a wide-spread condition which reaches epidemic proportions in industrialized countries, mainly in relation to current lifestyle and limited dietary sources. Epidemiological studies point towards an association between hypovitaminosis D and the presence of NAFLD and steatohepatitis (NASH), independently of confounders such as obesity and insulin resistance. Furthermore, several pieces of experimental data have shown the anti-fibrotic, anti-inflammatory and insulin-sensitizing properties exerted by vitamin D on hepatic cells. However, results from trials evaluating the effects of oral vitamin D supplementation on liver damage in NAFLD and NASH are controversial. The aim of this review is to give an overview of the evidence currently available from clinical trials and to discuss possible shortcomings and new strategies to be considered in future investigations.