Review article: the nutritional and pharmacological consequences of obesity surgery

Abstract

SUMMARY BackgroundObesity surgery is acknowledged as a highly effective therapy for morbidly obese patients. Beneficial short-term effects on common comorbidities are practically undisputed, but a growing data pool from long-term follow-up reveals increasing evidence of potentially severe nutritional and pharmacological consequences. AimsTo assess the prevalence, causes and symptoms of complications after obesity surgery, to elucidate and compare therapy recommendations for macro-and micronutrient deficiencies, and to explore surgically-induced effects on drug absorption and bioavailability, discussing ramifications for long-term therapy and prophylaxis. MethodsPubMed, Embase and MEDLINE were searched using terms including, but not limited to, bariatric surgery, gastric bypass, obesity surgery and Roux-en-Y, coupled with secondary search terms, e.g. anaemia, micronutrients, vitamin deficiency, bacterial overgrowth, drug absorption, pharmacokinetics, undernutrition. All studies in English, French or German published January 1980 through March 2014 were included. ResultsMacro-and micronutrient deficiencies are common after obesity surgery. The most critical, depending on surgical technique, are hypoalbuminemia (3-18%) and deficiencies of vitamins B 1 (≤49%), B 12 (19-35%) and D (25-73%), iron (17-45%) and zinc (12-91%). Many drugs commonly administered to obese patients (e.g. anti-depressants, anti-microbials, metformin) are subject to post-operative and/or PPI-associated changes affecting bioavailability and absorption. ConclusionsComplications are associated with pre-operative and/or post-operative malnutrition or procedure-related changes in intake, absorption and drug bioavailability. The high prevalence of nutrient deficiencies after obesity surgery makes life-long nutritional monitoring and supplementation essential. Post-operative changes to drug absorption and bioavailability in bariatric patients cast doubt on the validity of standard drug dosage and administration recommendations.

Medication and nutritional supplement use before and after bariatric surgery

“…57,58 Such deficiencies frequent occur after bariatric surgery and relate to decreased food intake and physiological changes produced by the surgery. 59,60 Gastric bypass changes how food passes along the gastrointestinal tract and leads to poor nutrient absorption, given that food is exposed to the jejunum earlier than usual, through exclusion of part of the gastric and duodenal surface. 61 The absorbent surface area and solubility, and consequently drug bioavailability, are affected by this technique.…”

Iron bioavailability from commercially available iron supplements

“…Another group that might benefit from both Spatone Apple ® and Iron Vital F ® are post-bariatric surgery patients who are at high risk of IDA [39][40][41], and in whom treatment with standard iron tablets is often ineffective [42,43]. In one study postoperative gastric bypass patients given 100 mg FeSO 4 tablets as an oral challenge absorbed inadequate amounts of iron as measured by change in serum iron concentration [44]; altered gut physiology after bariatric surgery may not allow for iron absorption from FeSO 4 tablets.…”

Zinc Deficiency after Gastric Bypass for Morbid Obesity: a Systematic Review

“…Its deficiency can lead to hair loss, diarrhoea, glossitis, nail dystrophy, hypogonadism in males, impotence, taste alteration, delayed wound healing, eye and skin lesions, and acrodermatitis enteropathica [2][3][4][5]. It can also be a cause of unexplained anaemia after gastric bypass and should be considered when routine screening for iron deficiency anaemia is negative [5][6].…”

“…Up to half [9][10][11][12][13] of bariatric surgery patients are deficient in Zn preoperatively and RYGB can further exacerbate it [4,9,12] through probably both reduced intake [15][16][17][18] and reduced absorption [15,19] as Zn is predominantly absorbed in the duodenum and the proximal jejunum.…”