Response to Letter to the Editor: Thiamine deficiency and bariatric surgery

We thank Dr. Morton for his letter regarding thiamine deficiency and bariatric surgery.

We agree that thiamine supplementation is of importance in patients at risk of deficiency such as in cases of malnutrition from decreased nutrient intake, increased nutrient losses, or impaired nutrient absorption. Clinical conditions where this may occur include starvation, hyperemesis gravidarum, and bariatric surgery. ¹ Our institution does not routinely conduct laboratory assessments of thiamine status. As described in the Journal of Parenteral and Enteral Nutrition tutorial on thiamine, in the acute care setting reliable laboratory tests are not available, are costly, and can be impractical due to the long turnaround time. ¹ Therefore, a clinical assessment of thiamine deficiency is conducted and the patient is treated if signs and symptoms point to a suspected deficiency. In addition, empiric treatment should be considered if the patient has evidence of malnutrition, even in the absence of symptoms of thiamine deficiency. In the case of our patient, the individual was indeed treated with parenteral thiamine during the commencement of total parenteral nutrition as she presented with malnutrition.

Laparoscopic sleeve gastrectomy (LSG) is not necessarily preferred over gastric bypass surgery (GBS) in individuals of reproductive age. In a 2014 retrospective study comparing the pregnancy outcomes and nutritional indices after GBS, biliopancreatic diversion (BPD), and LSG at a single institution, the researchers report good pregnancy outcomes in the sample population after all three surgeries provided that nutritional guidelines and supplementation are followed with close monitoring- especially for protein nutrition- after malabsorptive procedures. They suggest that individuals wait the recommended time period prior to attempting to conceive. ² At this time, clinical practice guidelines for bariatric surgery candidates of reproductive age do not recommend one surgery over another. ³ The Clinical Practice Guidelines for the Management of Overweight and Obesity in Adults, Adolescents and Children in Australia state that the choice of surgery is unique to the individual and takes into consideration age, access and commitment to services for follow up and continuing lifestyle interventions, as well as risk profile. ⁴ Guidelines from the British Obesity and Metabolic Surgery Society (BOMSS) inform that individuals who have undergone malabsorptive procedures such as the GBS, single anastomosis duodenal ileal bypass, BPD, or duodenal switch (DS) have a higher prevalence of post-surgery nutritional deficiencies. Therefore, care should be obtained at a specialist centre. Additionally, pregnant women following bariatric surgery should undergo nutritional screening during each trimester. ⁵

GBS is considered to be the gold standard surgery for obesity treatment. ⁶ A 2017 randomized control trial demonstrated that compared to LSG, GBS treated gastro-esophageal reflux disease and dyslipidemia more successfully. ⁶ A 2020 matched retrospective study demonstrated that both GBS and LSG achieved excellent diabetes remission and weight loss; however, GBS was associated with a significantly higher rate of discontinuation of diabetes medication at 24 months postoperatively and greater reduction in serum cholesterol and low-density lipoprotein-c levels. ⁷ Furthermore, a 2021 systematic review and meta-analysis found that when compared to the LSG, GBS resulted in greater decreases in BMI at 1 and 3 years post-op, higher remission of dyslipidemia, and lower low-density lipoprotein and total cholesterol levels. ⁸ These greater improvements following GBS would confer improved maternal health and pregnancy outcomes in the reproductive aged person since maternal obesity, which is defined as a BMI ≥ 30 kg/m² during pregnancy, increases the risk of pregnancy complications and poor fetal outcomes. ⁹ The BOMSS advise for women to avoid pregnancy for the first 12–18 months following surgery to allow for weight stabilization and a diversely nutritious diet. ⁵ Therefore, the time-to-conception interval is protective in optimizing maternal health prior to pregnancy and reducing any potential risks during pregnancy as a result of surgery. In the case of our patient, this individual had a malabsorptive BPD/DS procedure nine years prior to first pregnancy.

Particular attention is warranted if surgery occurred many years prior to pregnancy as loss to follow up and nutritional deficiencies are likely, which was demonstrated in our case. ³ As concluded in a 2021 systematic review and meta-analysis comparing LSG and GBS, long-term (>5 year) follow-up is necessary to provide valid data on the relative effectiveness of GBS and LSG for long-term weight loss. ⁸ This data could provide further direction on the most appropriate choice of surgery for reproductive aged individuals considering some individuals may have surgery at a relatively younger age and not become pregnant until many more years later.