Intestinal calcium absorption in patients after jejuno-ileal bypass or small intestinal resection and the effect of vitamin D

Vitamin D and intestinal calcium transport after bariatric surgery

Bariatric surgery is a highly effective treatment for obesity, but it may have detrimental effects on the skeleton. Skeletal effects are multifactorial but mediated in part by nutrient malabsorption. While there is increasing interest in non-nutritional mechanisms such as changes in fat-derived and gut-derived hormones, nutritional factors are modifiable and thus represent potential opportunities to prevent and treat skeletal complications. This review begins with a discussion of normal intestinal calcium transport, including recent advances in our understanding of its regulation by vitamin D, and areas of continued uncertainty. Human and animal studies of vitamin D and intestinal calcium transport after bariatric surgery are then summarized. In humans, even with optimized 25-hydroxyvitamin D levels and recommended calcium intake, fractional calcium absorption decreased dramatically after Roux-en-Y gastric bypass (RYGB). In rats, intestinal calcium absorption was lower after RYGB than after sham surgery, despite elevated 1,25-dihyroxyvitamin D levels and intestinal gene expression evidence of vitamin D responsiveness. Such studies have the potential to shed new light on the physiology of vitamin D and intestinal calcium transport. Moreover, understanding the effects of bariatric surgery on these processes may improve the clinical care of bariatric surgery patients.

IMPACT OF VITAMIN D AND CALCIUM DEFICIENCY IN THE BONES OF PATIENTS UNDERGOING BARIATRIC SURGERY: A SYSTEMATIC REVIEW

Introduction:

Bariatric surgery is considered the most effective tool in the control and treatment of severe obesity, but patients undergoing this procedure are at increased risk of developing nutritional deficiencies by limiting the intake and absorption of many nutrients.

Objective:

To assess the impact of vitamin D deficiency and calcium in bone in patients after gastric bypass in Roux-en-Y, pointing directly at the type of administration, doses and effects after surgery.

Method:

Was conducted a systematic review with articles related to the topic of the last 10 years searched in PubMed (US National Library of Medicine National Institutes of Health, Medline, Lilacs, Scielo and Cochrane using the headings "bariatric surgery", "bone", "obesity", "vitamin D '', "calcium" AND "absorption". Exclusion criteria to research on animals, smokers, pregnant women and patient treated with bisphosphonates.

Results:

Five articles were included in this review. All refer that bariatric surgery can lead to nutritional deficiencies and poor absorption of fats and fat-soluble vitamins and other micronutrients such as calcium.

Conclusion:

Patients submitted to RYGB should make use of multivitamins and minerals especially vitamin D and calcium to prevent bone fractures. Monitoring, treatment and control of risk factors are essential to prevent complications after this operation.

True fractional calcium absorption is decreased after Roux-en-Y gastric bypass surgery

OBJECTIVE

Roux-en-Y gastric bypass (RYGB) is considered to be the gold standard alternative treatment for severe obesity. Weight loss after RYGB results primarily from decreased food intake. Inadequate calcium (Ca) intake and metabolic bone disease can occur after gastric bypass. To our knowledge, whether malabsorption of Ca contributes to an altered Ca metabolism in the RYGB patient has not been addressed previously.

RESEARCH METHODS AND PROCEDURES

We recruited 25 extremely obese women in order to study true fractional Ca absorption (TFCA) before and 6 months after RYGB surgery, using a dual stable isotope method ((42)Ca and (43)Ca) and test load of Ca (200 mg). Hormones regulating Ca absorption and markers of bone turnover were also measured.

RESULTS

In 21 women (BMI 52.7 +/- 8.3 kg/m(2), age 43.9 +/- 10.4 years) who successfully completed the study, TFCA decreased from 0.36 +/- 0.08 to 0.24 +/- 0.09 (p < 0.001) after RYGB. Bone turnover markers increased significantly (p < 0.01). TFCA correlated with estradiol levels (r = 0.512, p < 0.02) and tended to correlate with 1,25 (OH)(2)D (r = 0.427, p < 0.06) at final measurement. Stepwise linear regression indicated that estradiol explained 62% of the variance for TFCA at 6 months post-surgery (p < 0.01).

DISCUSSION

TFCA decreases (0.12 +/- 0.08) after RYGB surgery but remains within normal range. Although only some patients were estimated to have low Ca absorption after surgery, all of the patients showed a dramatic increase in markers of bone resorption. The alteration in Ca metabolism after RYGB-induced weight loss appears to be regulated primarily by estradiol levels and might ultimately affect bone mass.

Metabolic bone disease in IBD

A substantial number of patients with inflammatory bowel disease (IBD) will manifest extra-intestinal complications. Metabolic bone disease and arthropathies are among the most debilitating of these. Decreased bone mineral density and increased fracture risk may occur in relation to the underlying disease itself or result from vitamin, mineral, and hormonal deficiencies; medications used to treat the underlying disease; lifestyle; and perhaps other factors. In many cases, the factors remain unidentified. Options for the treating clinician include correction of these deficiencies, treatment of the underlying disease, and use of medication to promote bone formation and decrease bone resorption.

Bones and Crohn's: problems and solutions

Inflammatory bowel disease may manifest in various extra intestinal manifestations. Osteopenia and various arthropathies may be debilitating. These may be related to the disease itself, patient genetics, lifestyle, or disease treatment. Calcium and vitamin D malabsorption, vitamin K deficiency, malnutrition, corticosteroid and other immunosuppressive medications, smoking, lack of exercise and postmenopausal state may all play important roles. Treatment may be undertaken to correct nutrient deficiencies, inhibit bone resorption and increase bone formation.