Obesity is a complex, multifactorial chronic disease with an escalating global incidence, impacting over 650 million adults worldwide. It is closely linked to a variety of metabolic, cardiovascular, and musculoskeletal diseases, and is a leading contributor to preventable morbidity and mortality. Metabolic and Bariatric Surgery (MBS) stands out as the most effective long-term intervention for obesity, facilitating significant and sustained weight loss while also promoting remission of associated diseases.

However, the anatomical and physiological alterations induced by MBS, including gastric restriction, bypass of absorptive surfaces, altered gastrointestinal transit, and reduced gastric acid production, significantly disrupt nutrient absorption and metabolism, placing patients at lifelong risk of micronutrient deficiencies or, conversely, hypervitaminosis resulting from excessive supplementation. Among these, Vitamin B6 imbalance has emerged as a significant yet under-recognized issue in post-MBS patients.

Among the nutrients affected, vitamin B6 (pyridoxine) presents a unique challenge. Vitamin B6 functions as a coenzyme in amino acid metabolism, neurotransmitter synthesis, and immune regulation. Deficiencies in Vitamin B6 are well-documented and can manifest as glossitis, irritability, and peripheral neuropathy. Notably, B6-related neuropathy may clinically resemble Guillain-Barré syndrome in post-MBS patients. This anxiety surrounding deficiency symptoms often leads to the overconsumption of Vitamin B6, resulting in hypervitaminosis, which can also present with neurological manifestations such as sensory neuropathy and ataxia.

The risk of hypervitaminosis is further exacerbated by the widespread use of high-dose multivitamin formulations post-surgery, many of which contain vitamin B6 at levels far exceeding the Recommended Dietary Allowance (RDA). For males, the RDA is 1.3 mg daily for those aged 19-50 years, increasing to 1.7 mg for those over 50. For females, the RDA is 1.3 mg for those aged 19-50 and 1.5 mg for those over 50. Yet some commercially available bariatric supplements exceed this level several-fold. Studies by Dogan et al. and Homan et al. emphasize the prevalence of vitamin B6 toxicity in post-MBS populations, largely attributable to inappropriate supplementation practices.

To address this, the Elan series of bariatric-specific supplements (Believe, Compass, and Supreme) was developed with standardized and conservative B6 dosing (400 micrograms per day), approximately 29% of the adult RDA. Each formulation is tailored to the nutritional demands of a specific MBS procedure, while maintaining a uniform B6 dose to facilitate direct comparisons of B6 status across surgical types.

To date, no prospective, randomized study has evaluated the effect of procedure-specific supplementation on the risk of vitamin B6 hypervitaminosis in post-bariatric patients. This trial aims to fill that gap by comparing standardized B6 supplementation outcomes across three common MBS procedures: sleeve gastrectomy (SG), Roux-en-Y gastric bypass (RYGB), and one-anastomosis gastric bypass (OAGB).

In addition to assessing the prevalence of B6 toxicity and deficiency, the study will evaluate broader micronutrient status, anthropometric outcomes, and adherence to supplementation. Findings from this trial are expected to inform the design of safer, procedure-matched supplementation protocols for post-MBS care.

Inclusion Criteria:

Eligible participants will be adults:

• Aged 18 to 65 years
• Undergoing primary metabolic and bariatric surgery (MBS), including sleeve gastrectomy (SG), Roux-en-Y gastric bypass (RYGB), or one anastomosis gastric bypass (OAGB).
• Patients must meet established surgical indications as defined by the International Federation for the Surgery of Obesity and Metabolic Disorders (IFSO), specifically: a body mass index (BMI) greater than 30 kg/m² with at least one obesity-related comorbidity (e.g., type 2 diabetes, hypertension, obstructive sleep apnea)
• or a BMI greater than 35 kg/m² irrespective of comorbidities.
• Eligible participants must be capable of providing informed consent, willing to adhere to the prescribed supplement regimen, and able to complete scheduled postoperative follow-up visits for 12 months.

Exclusion Criteria:

Exclusion criteria include:

• Revision or secondary MBS procedures
• Known hypersensitivity to vitamin B6 or any component of the supplement formulations
• Pregnancy or planned pregnancy during the study period
• Any pre-existing medical condition known to interfere with vitamin B6 metabolism. This includes, but is not limited to, severe hepatic or renal dysfunction, peripheral neuropathy, and the use of medications such as isoniazid, phenytoin, or levodopa. Additional exclusions include chronic gastrointestinal conditions affecting absorption (e.g., inflammatory bowel disease, celiac disease), porphyria, or any other clinical scenario that, in the judgment of the investigators, may compromise compliance or the reliability of follow-up.
• Patients who are already receiving high-dose vitamin B6 supplementation or have abnormal preoperative B6 levels will be excluded.

The analysis will be performed on a blinded dataset after completing the medical/scientific review. All protocol violations will be identified and resolved, and the dataset will be declared complete. All data will be collected in a data management system (Castor EDC, Amsterdam, The Netherlands; https://www.castoredc.com), handled according to Good Clinical Practice guidelines, Data Protection Directive certificate, and complied with Title 21 CFR Part 11. Furthermore, the data centers where all the research data will be stored are certified according to ISO27001, ISO9001, and Dutch NEN7510.

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