LAUSR

Dear Editor, Many thanks for your kind invitation to comment on this letter in response to the article [1] published recently in Obesity Surgery. First of all, it is important to understand what Bailly et al. [1] found in their study. They found that amongst those who were hospitalised in France, for one reason or other, and had undergone a primary bariatric procedure between 2008 and 16, anaemia due to micronutrient deficiency was more likely to be listed as the main or related diagnoses in those who underwent a gastric bypass (GB) compared to those who underwent a sleeve gastrectomy (SG). Authors of this letter point out that others [2] have found anaemia rates to be higher with SG than GB, Roux-en-Y gastric bypass (RYGB) in particular. They further contend that the results might be due to the possibility that GB cohort in the study by Bailly et al. [1] includes a large number of patients who underwent one anastomosis gastric bypass (OAGB)—an increasingly popular procedure in France. This letter, and the study by Bailly et al. [1], raises several interesting and inter-related points, that I would seek your permission to highlight. First of all, it is now well known that patients undergoing bariatric surgery suffer from a range of micronutrient deficiencies even prior to surgery [3]. Bariatric surgery can further exacerbate these deficiencies through a combination of reduced intake and absorption. This is the reason that authoritative societies recommend routine supplementation of various essential micronutrients after all bariatric procedures [4, 5]. At the same time, one has to recognise that evidence base on how much of each of these micronutrients needs to be supplemented after each procedure has yet to be scientifically determined. If we know the optimum supplementation dose of each micronutrient after each procedure, we would dramatically reduce both subclinical as well as clinical micronutrient deficiencies, and by implication correct any pre-existing nutritional anaemia—not cause it. We have tried to examine the appropriate doses of some of these micronutrient supplementations for RYGB patients [6–8] but to do the same for all important micronutrients after all common bariatric procedures will need a significant collective effort. Compliance with a range of micronutrient supplementation that often results in patients taking many tablets (and sometimes injections) is another major issue following bariatric surgery. If we could identify how much of each of the important micronutrients need to be supplemented after each of our procedures and package them into a pill, we would be able to improve patient compliance and reduce micronutrient deficiency. These issues are important because SG patients in the study by Kheniser et al. [2] were advised a different supplementation regime to RYGB patients and one could argue that their protocol for RYGB was more effective in preventing anaemia than one for SG. It was presumed in the past, perhaps somewhat erroneously, that patients undergoing SG do not need iron or calcium supplementation beyond what one could obtain from an over the counter multivitamin tablet. We now know that even though SG does not bypass proximal small bowel, the predominant site for absorption of some of these micronutrients, it necessarily reduces calorie intake significantly and therefore results in a reduced intake of micronutrients. It would indeed be impossible to consume the desired daily recommendations of each of these micronutrients on a daily basis within the framework of a significantly reduced calorie intake from any bariatric procedure. To conclude, it is possible that OAGB patients have a further reduction in capacity to absorb iron compared to those undergoing RYGB and this may well account for the suggested increase in anaemia rates following GB by Bailly et al. [1]. In fact, we have noticed [9] a trend towards lower iron levels and higher anaemia rates in our OAGB patients compared to our RYGB patients given exactly the same doses of various supplements. If you put this finding against our another observation [10] that approximately 48.5% (n = 101/ * Kamal Mahawar [email protected]