Three Important Things You Must Know About Bone Health after Gastric Bypass Surgery
By Ronda L. Hart, MSN APRN-BC CBN
With the growing obesity epidemic worldwide, bariatric surgery is the appropriate treatment option for some to achieve significant, sustainable weight loss. These surgeries utilize techniques that restrict the amount of food that can be eaten, limit the absorption of calories, or combine both of these elements. While weight loss provides indisputable improvement in co-morbidities such as diabetes and hypertension, there is growing evidence that significant weight loss can negatively affect bone health, particularly after gastric bypass.
Calcium absorption is impaired after gastric bypass surgery as there is significantly less stomach acid (needed to absorb calcium), as well as malabsorption from bypassing the duodenum. Due to fat malabsorption, severe vitamin D deficiency will develop along with the already reduced ability to absorb calcium (Fujioka, 2005). In general, fat-soluble vitamins A, D, and K will be deficient in two-thirds of bypass patients within 4 years after surgery. Up to 50% will have hypocalcemia, and nearly all of these patients with low vitamin D levels will have secondary hyperparathyroidism (increased parathyroid hormone production secondary to hypocalcemia). In one study, bone demineralization from secondary hyperparathyroidism was found in 29% of post gastric bypass patients (time from surgery varied from 1 to 9 years) [Fujioka, 2005].
In addition, increased bone turnover and reduced bone mineral density may occur as a physiological change because of decreased mechanical loading of the skeleton, or as a pathophysiological response to the surgery (Fleischer, 2008).
Confounding these problems, pre-existing Vitamin D deficiency, very commonly found in people who are obese, may pre-date surgery and contribute to postoperative change in bone metabolism. Sixty-four percent of all patients were found to suffer from a vitamin D deficiency and 14% were found to have elevated PTH preoperatively (DiGiorgi, 2008).
Because of pre-surgical deficiencies, several studies have recommended screening and treating calcium and vitamin D deficiencies prior to surgery in an effort to forestall or limit bone loss postoperatively. Some authors recommend baseline dual-energy x-ray absorptiometry (DXA) scans as well (Boschert, 2011).
Despite pre-op normalization of these levels, and supplementation post-operatively, there is still evidence of calcium and vitamin D malabsorption and secondary hyperparathyroidism early in the postoperative period despite marked increases in calcium (100%) and vitamin D (260%) intake (Fleischer, 2008). Postoperatively, a decline in bone mineral density was strongly associated with the amount of weight loss itself (Fleischer, 2008). Common symptoms of bone demineralization can be joint pain or swollen joints. Frequently the first presenting symptom of demineralization is a fracture or broken bone.
To keep an eye on your calcium levels, be sure to see you physician to be followed with blood work. Your physician will treat accordingly with an adjustment in calcium or Vitamin D intake. In addition, several studies recommend DXA scan annually for continued documentation of bone health.
References
Boschert, S. (2011). Bariatric surgery can lead to bone loss. Internal Medicine News (http://www.internalmedicinenews.com/specialty-focus/osteoporosis/single-article-page/bariatric-surgery-can-lead-to-bone-loss.html)
DiGiorgi, M. (2008). Markers of bone and calcium metabolism following gastric bypass and laparoscopic adjustable gastric banding.Obesity Surgery, 9, 1144-1148.
Fleischer, J., Stein, E.M., Bessler, M., Della Badia, M., Restuccia, N., Olivero-Rivera, L., McMahon,D.J., & Silverberg, S.J. (2008). The decline in hip bone density after gastric bypass surgery is associated with extent of weight loss. The Journal of Clinical Endocrinology and Metabolism, 93(10), 3735–3740.
Fujioka, K. (2005). Follow-up of nutritional and metabolic problems after bariatric surgery. Diabetes Care, 28, 481–484.
Grever, J. (2008). Alteredcalcium metabolism after bariatric surgery prompts bone loss, Med Page Today, 1-5. (http://www.medpagetoday.com/primarycare/obesity/11027).
