Vitamin D is integral to maintaining normal calcium levels by aiding calcium absorption. Vitamin D deficiency is very common before bariatric surgery and remains a concern afterwards. Here is what the science says about vitamin D deficiency pre- and post-bariatric surgery, and how bone health is evaluated and managed.
Key takeaways
- Deficiency rates of 71.4–89.7% have been reported before surgery, rising with BMI.
- Bariatric surgery can reduce bone mineral density, but adequate supplementation can mostly reverse this.
- Routine preventive supplementation: calcium 1,200–1,500 mg/day and vitamin D 3,000 IU/day.
Pre-operative period
People with obesity have greater fat mass, so more vitamin D is required to maintain normal concentrations, because vitamin D is sequestered in fat cells.1 Peterson et al. found a deficiency rate of 71.4% among 58 patients studied, with most deficiency in minority ethnic groups. Melanin concentration in the skin is a risk factor for vitamin D deficiency, as melanin inhibits vitamin D synthesis.1 Another study showed that 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 25 nmol/l. As BMI increased, the rate of vitamin D deficiency also increased.2
Post-operative period
There is evidence that weight loss procedures can negatively affect bone mineral density, accelerate bone loss and increase bone fragility.3 However, these effects can mostly be reversed with adequate supplementation after surgery.4 Serum calcium levels often remain within normal limits after surgery due to the body's regulatory pathways. Unfortunately, people with obesity typically have abnormal 25(OH)D levels due to sequestration of vitamin D in fat tissue and a sedentary lifestyle with less sunlight exposure.4 It is believed that changes in gut hormone concentrations after sleeve gastrectomy can cause vitamin D deficiency after surgery.5
- Fracture risk (Lu et al.): a twelve-year study found that of 1,775 patients who had a restrictive procedure, 154 (8.7%) had fractures. Fracture rates were 1.6% at 1 year, 2.37% at 2 years, 1.69% at 5 years and 2.06% after more than 5 years, mostly in the extremities.3
- Mihmanli et al.: of 119 patients after sleeve gastrectomy, 32.7% needed high-dose vitamin D supplementation to combat deficiency 12 months after surgery.5
- Carrasco et al.: vitamin D deficiency in sleeve gastrectomy patients was 31.6% pre-op, 5.6% at 6 months and 15.8% at 12 months; hyperparathyroidism was 57.9% pre-op, 31.6% at 6 months and 5.3% at 12 months. Patients with higher vitamin D and calcium intake from diet and supplements had lower parathyroid hormone levels, and calcium intake closer to ASMBS recommendations was associated with less bone loss in the lumbar spine.6
- Pluskiewicz et al.: bone mineral density fell by 1.2% in the spine, 7% in the femoral neck and 5.3% in the total hip 6 months after sleeve gastrectomy.7
Below is a review of the evaluation and management of bone health in surgical patients (table 1) and recommendations for calcium and vitamin D supplementation (table 2).8
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 over 65, men over 70 and patients with conditions associated with bone loss or low bone mass | 1,200–1,500 mg/day. Monitor serum parathyroid hormone, calcium and 25(OH)D every 6–12 months, then annually. DXA of spine and hip 2 years post-op, then every 2–5 years | Evaluate secondary causes if bone mass is low pre-op. Consider bisphosphonates when the bone density T-score is below −2.5 |
| Vitamin D | 25(OH)D, serum parathyroid hormone | 3,000 IU/day needed to reach 25(OH)D above 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 deficiency: more than 3,000 and less than 6,000 IU vitamin D3/day, or 50,000 IU vitamin D2 1–3 times a week. Severe malabsorption may require higher doses of up to 50,000 IU D2 or D3 1–3 times a week to once daily. High vitamin D doses should be given for a limited period and monitored by medical professionals |
| Protein | Serum albumin; serum protein, pre-albumin and DXA of fat-free mass can also be measured | 60–80 g/day or 1.1–1.5 g/kg ideal body weight. Monitor serum albumin at 6–12 months, then annually | Oral protein supplementation or enteral/parenteral nutrition as needed |
| Physical activity | N/A | Moderate aerobic physical activity of at least 150 minutes/week, with a goal of 300 minutes/week. Strength training 2–3 times a week | 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 above 65 pg/ml | 25(OH)D reference range 30–100 ng/ml; preferred range 30–50 ng/ml; insufficiency 20–30 ng/ml; deficiency below 20 ng/ml |
| Routine preventive supplementation | 1,200–1,500 mg/day | 3,000 IU/day |
| Supplemental source | Calcium citrate is preferred over calcium carbonate, as its absorption does not depend on stomach acidity | D3 is more potent than D2, but both can be effective and are dose-dependent |
| Additional considerations | Divided doses of no more than 600 mg, at least 2 hours apart from iron-containing products; calcium carbonate should be taken with meals, calcium citrate with or without meals | For best absorption, take vitamin D with meals containing a fat source |
| Tolerable upper intake level | 19–50 years: 1,500 mg/day; over 51 years: 2,000 mg/day; pregnancy/lactation: 2,500 mg/day | Over 9 years: 4,000 IU/day |
| Safety and risk assessment | Potential adverse effects of excess intake include increased risk of kidney stones, constipation, hypercalciuria, hypercalcaemia, vascular and soft tissue calcification, renal insufficiency and interference with the absorption of other minerals | Contraindications include hypercalcaemia or metastatic calcification. Serum 25(OH)D chronically above 50 ng/ml may be related to potential adverse effects; above 100 ng/ml reflects excess vitamin D, above 150 ng/ml indicates intoxication. Doses below 10,000 IU/day are unlikely to cause toxicity in adults. Excessive vitamin D intake is associated with hypercalcaemia, hypercalciuria and kidney stones (when combined with excess calcium supplementation). In sensitive subgroups (granuloma-forming disorders, chronic fungal infections, lymphoma, thiazide diuretic treatment), 25(OH)D and calcium should be monitored carefully. Monitor serum calcium 1 month after completing a high-dose vitamin D loading regimen; if calcium is elevated, stop any calcium-containing vitamin D supplements and delay further loading. Elevated calcium despite stopping calcium and vitamin D supplements requires PTH monitoring and referral to an 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
High-dose vitamin D should only be taken under medical supervision. Your bariatric team will determine your doses based on your blood tests.
Sources
- Peterson LA, Cheskin LJ, Furtado M, et al. Malnutrition in bariatric surgery candidates: multiple micronutrient deficiencies prior to surgery. Obes Surg. 2016;26:833–838. https://doi.org/10.1007/s11695-015-1844-y
- Ernst B, Thurnheer M, Schmid SM, et al. Evidence for the necessity to systematically assess micronutrient status prior to bariatric surgery. Obes Surg. 2009;19:66–73. 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
This article is for general information only and does not replace personal medical advice. Always discuss your situation, blood test results and supplementation with your bariatric team or healthcare provider.