Pre-Operative Period
Vitamin D is integral in maintaining normal calcium levels by aiding in absorption. Individuals who are obese have greater fat mass, so more vitamin D is required to maintain normal concentrations, due to the fact that vitamin D is segregated in adipose cells1. Peterson et al. noted a deficiency rate of 71.4% out of 58 patients studied, with the majority of deficiency presenting in minority races. Melanin concentrations in the skin present as a risk factor for vitamin D deficiency, with increased concentrations providing a greater risk due to the fact that melanin inhibits vitamin D synthesis1. Another study showed 89.7% of patients had 25-OH-D levels below 76.0 nmol/l, 61.2% below 50.0 nmol/l, and 25.4% below 25nmol/l. As BMI increased across the study population, the rate of vitamin D deficiencies also increased2.
Post-Operative Period
There is evidence that suggests weight loss procedures can cause a negative effect on bone mineral density, accelerate bone loss, and increase bone fragility3. However, these negative effects can mostly be reversed with adequate supplementation after surgery4. Serum calcium levels often remain within normal limits in post-operative patients, due to the regulatory pathways in the body. Unfortunately, obese individuals typically have abnormal 25(OH)D levels due to sequestration of vitamin D within adipose tissue, as well as due to a sedentary lifestyle with reduced sunlight exposure4. It's believed that changes in gut hormone concentrations after the sleeve gastrectomy can cause vitamin D deficiency in post-operative patients5.
Lu et al. conducted a twelve-year study to observe fracture risk in bariatric surgery patients. Their results showed that out of the total 1,775 patients that had a restrictive procedure, 154 patients (8.7%) had fractures. The fracture rate for the surgical group were: 1.6% at 1 year, 2.37% at 2 years, 1.69% at 5 years, and 2.06% at greater than 5 years, with most fractures occurring in the extremities3.
Likewise, Mihmanli et al. studied 119 post-sleeve gastrectomy patients and their vitamin D levels during the first year after surgery. At 12 months post-surgery, 32.7% of patients needed high-dose vitamin D supplementation to combat deficiency5.
Carrasco et al. noted vitamin D deficiency in sleeve gastrectomy patients as being 31.6% pre-op, 5.6% at 6 months, and 15.8% at 12 months after surgery. Coincidentally, hyperparathyroidism was observed in 57.9% pre-op, 31.6% at 6 months, and 5.3% at 12 months post-surgery. Bariatric patients who achieved higher vitamin D and calcium intake via diet and supplementation had reduced parathyroid hormone levels. Calcium intake of patients, closer to ASMBS recommendations, showed an association with less bone loss in the lumbar region of the spinal cords of sleeve gastrectomy patients6.
Pluskiewicz et al. noted bone mineral density reductions of 1.2% in the spine, 7% in femoral neck, and 5.3% in total hip in sleeve gastrectomy patients 6 months post-surgery7. A review of evaluation and management of bone health in the surgical patient (Table 1) and recommendations for calcium and vitamin D supplementation (Table 2) are described below8
Table 1-Evaluation and Management of Bone Health in Surgical Patients
| Parameter | Pre-Op Management | Post-Op Management | Treatment |
| Calcium | Serum parathyroid hormone, serum calcium, 25(OH)D, DXA of spine and hip for women age >65, men age > 70, patients with conditions associated with bone loss or low bone mass | 1200-1500 mg/d. Monitor serum parathyroid hormone, calcium, and 25(OH)D every 6-12 months and then annually. DXA at spine and hip 2 years post-op, then every 2-5 years | Evaluate secondary causes if bone mass is low in pre-op phase. Consider bisphosphonates when bone density T score is <2.5 |
| Vitamin D | 25 (OH)D, serum parathyroid hormone | 3000 IU/d needed to reach 25(OH)D >30 ng/ml. Monitor serum parathyroid hormone and 25(OH)D every 6-12 months, then annually. 24-hour urinary calcium at 6 months, then annually | For rapid correction of vitamin D deficiency >3,000 IU and <6,000 IU vitamin D3/d or 50,000 IU vitamin D2 1-3 times/week. Severe malabsorption may require higher dosing of <50,000 IU D2 or D3 1-3 times/week to once daily. High vitamin D dosing should be administered over a limited period of time and should be monitored by medical professionals |
| Protein | Serum albumin; can also measure serum protein, pre-albumin, DXA of fat-free mass | 60-80 g/d or 1.1-1.5 g/kg ideal body weight. Monitor serum albumin 6-12 months and then annually | Oral protein supplementation or enteral/parenteral nutrition as needed |
| Physical Activity | N/A | Moderate aerobic physical activity at minimum 150 minutes/wk with a goal of 300 min/wk. Strength training 2-3 times/wk | N/A |
Adapted from Ben-Porat T, Elazary R, Sherf-Dagan S, et al. Bone Health following Bariatric Surgery: Implications for Management Strategies to Attenuate Bone Loss. Adv Nutr. 2018;9(2):114‐127. doi:10.1093/advances/nmx024
Table 2- Recommendations for Calcium and Vitamin D Supplementation
| Calcium | Vitamin D | |
| Threshold values |
Serum calcium (without renal disease): 9-10.5 mg/dl Serum parathyroid hormone: hyperparathyroidism >65 pg/ml |
25(OH)D: reference range 30-100 ng/ml; preferred range: 30-50 ng/ml; insufficiency: 20-30 ng/ml, deficiency <20ng/ml |
| Routine preventative supplementation | 1200-1500 mg/d | 3000 IU/d |
|
Supplemental source |
Calcium citrate is preferred over calcium carbonate, due to it being independent of stomach acidity absorption | D3 is more potent than D2, but both can be effective and dose-dependent |
| Additional Considerations | Divided doses no greater than 600 mg; separated by at least 2 hours from iron-containing products; calcium carbonate should be taken with meals, while calcium citrate can be taken with or without meals | For best absorption, vitamin D should be taken with meals containing a fat source |
| Tolerable daily upper intake level | 19-50 yrs: 1500 mg/d, >51 yrs:2000 mg/d, pregnancy/lactation:2500 mg/d | >9 yrs: 4000 IU/d |
| Safety and Risk Assessment | Potential adverse effects of excess intake include increased risk of kidney stones, constipation, hypercalciuria, hypercalcemia, vascular and soft tissue calcification, renal insufficiency, and interference with another mineral’s absorption |
Contraindications for vitamin D supplementation include patients with hypercalcemia or metastatic calcification Serum 25OHD chronically >50 ng/mL may be related to potential adverse effects. Levels of 25(OH)D >100 ng/mL reflect excess of vitamin D, levels of 25(OH)D >150 ng/mL indicating intoxication. Vitamin D doses <10,000 IU/d are unlikely to cause toxicity in adults. Excessive vitamin D intake is associated with clinical adverse effects including hypercalcemia, hypercalciuria, and renal stones (when taken together with excess calcium supplementation) In sensitive subpopulations (granuloma-forming disorders, chronic fungal infections, lymphoma, thiazide diuretics treatment), 25(OH)D and calcium levels should be monitored carefully. Serum calcium levels should be monitored 1 month after completing the loading regimen of high-dose vitamin D supplements to treat deficiency. If calcium levels are elevated, any calcium-containing vitamin D supplements should be stopped, and further vitamin D loading should be delayed. Elevated calcium despite stopping calcium and vitamin D supplements requires PTH monitoring and referral to endocrinologist |
Adapted from Ben-Porat T, Elazary R, Sherf-Dagan S, et al. Bone Health following Bariatric Surgery: Implications for Management Strategies to Attenuate Bone Loss. Adv Nutr. 2018;9(2):114‐127. doi:10.1093/advances/nmx024
References:
- Peterson, L.A., Cheskin, L.J., Furtado, M. et al. Malnutrition in Bariatric Surgery Candidates: Multiple Micronutrient Deficiencies Prior to Surgery. OBES SURG 26, 833–838 (2016). https://doi.org/10.1007/s11695-015-1844-y
- Ernst, B., Thurnheer, M., Schmid, S.M. et al. Evidence for the Necessity to Systematically Assess Micronutrient Status Prior to Bariatric Surgery. OBES SURG 19, 66–73 (2009). https://doi.org/10.1007/s11695-008-9545-4
- Lu CW, Chang YK, Chang HH, et al. Fracture Risk After Bariatric Surgery: A 12-Year Nationwide Cohort Study. Medicine (Baltimore). 2015;94(48):e2087. doi:10.1097/MD.0000000000002087
- Folli F, Sabowitz BN, Schwesinger W, Fanti P, Guardado-Mendoza R, Muscogiuri G. Bariatric surgery and bone disease: from clinical perspective to molecular insights. Int J Obes (Lond). 2012;36(11):1373‐1379. doi:10.1038/ijo.2012.115
- Mihmanli M, Isil RG, Isil CT, et al. Effects of Laparoscopic Sleeve Gastrectomy on Parathyroid Hormone, Vitamin D, Calcium, Phosphorus, and Albumin Levels. Obes Surg. 2017;27(12):3149‐3155. doi:10.1007/s11695-017-2747-x
- Carrasco F, Basfi-Fer K, Rojas P, et al. Changes in bone mineral density after sleeve gastrectomy or gastric bypass: relationships with variations in vitamin D, ghrelin, and adiponectin levels. Obes Surg. 2014;24(6):877‐884. doi:10.1007/s11695-014-1179-0
- Pluskiewicz W, Buzga M, Holeczy P, Bortlik L, Smajstrla V, Adamczyk P. Bone mineral changes in spine and proximal femur in individual obese women after laparoscopic sleeve gastrectomy: a short-term study. Obes Surg 2012;22(7):1068–76
- Ben-Porat T, Elazary R, Sherf-Dagan S, et al. Bone Health following Bariatric Surgery: Implications for Management Strategies to Attenuate Bone Loss. Adv Nutr. 2018;9(2):114‐127. doi:10.1093/advances/nmx024
