In the setting of prophylactic post-surgical micronutrient prescription, this study found the majority of micronutrients did not appear vulnerable to increased deficiency prevalence in the first 12 months after bariatric surgery, even when supplement targets were, mostly, not met. The low rates of surgical-induced micronutrient deficiency was observed within a model of care where participants received frequent and consistent expert multidisciplinary care pre- and post-operatively, including education on prophylactic supplementation, and monitoring of biochemical micronutrient markers, dietary intake and postoperative surgical complications.
These results indicate that de novo deficiency was uncommon, with higher risk for deficiencies identified only in some key nutrients. Although the need for prophylactic micronutrient supplementation continues, these results begin to challenge the need for high doses of all ten nutrients within prophylactic multivitamin prescription after SG or GB, where the limb length is ≤ 150cm, particularly when patients are supported in a multidisciplinary post-operative setting (2, 3). Although supplementation intake increases after surgery, doses of calcium, vitamin B12 and iron were met by < 20% of patients without incidence of deficiency. Additionally, vitamin D deficiency decreased after SG despite less than one third of participants meeting vitamin D supplement targets at any timepoint. However, these results indicate that supplementation may only have an independent role in preventing deficiency in folate (after both procedures) and vitamin B1 (after GB) and therefore suggests prioritising the recommended high doses of these nutrients in multivitamins. The lower than expected risk for micronutrient deficiencies despite lower than prescribed exposure to supplementation challenges current blanket recommendations for high dose broad prophylactic supplementation.
The independent relationship between inflammation and ferritin is recognised (20), however the impact of chronic obesity-related inflammation and surgery on other micronutrients remains poorly recognised. Unsurprisingly, prevalence of inflammation was high pre-operatively and bariatric surgery had a remarkable dampening effect by 6–12 months (21). This is the first study to consider the impact of inflammation when interpreting micronutrient status before and after bariatric surgery. In the presence of inflammation ferritin, copper and vitamin B1 levels appeared to increase while vitamin A and potentially plGPx levels decreased. While this association has been observed in the general population for ferritin, vitamin A, vitamin B1 and copper (9, 17, 20), little data exists in a bariatric surgical setting. Furthermore, plGPx’s independent relationships with glycemic control and inflammation reflect its role in oxidative stress (11, 12). Although selenium is a rate limiting factor to plGPx activity if body stores are low, this finding suggests that in a population with increased oxidative stress or high HbA1c, this functional marker may not be the most reliable measure of selenium status and should be interpreted with caution (11, 12). Overall, this study suggests an assessment of systemic inflammation appears important when interpreting micronutrient status in a bariatric population, which is not included in current perioperative bariatric surgery guidelines (2, 3). In particular, in a setting of reduced levels of selenium or vitamin A, to stimulate an investigation and treatment of any co-existent inflammation in addition to increasing supplement dosage as a multipronged approach to correction.
These results may also inform rationalising the testing frequency of some nutrients in the first postoperative year. ASMBS practice guidelines recommend testing up to 10 nutrients, up to four times within the first post-operative year (2). However, more recent BOMSS guidelines, have moved towards a more individualised testing schedule, suggest only five nutrients up to three times in the first year, with other nutrients be tested as required or annually (3). This study found that after SG, only folate and potentially iron, appeared vulnerable to deficiency 6 months after surgery. Additionally, after GB only vitamin B1 and folate appeared vulnerable to deficiency due to surgery, with uncertainty remaining about the potential risk vitamin D deficiency. While low plGPx and vitamin A deficiency prevalence did increase after surgery, both were independently related to inflammation and/or glycaemic control, not time since surgery, suggesting mechanisms other than surgically induced malabsorption are playing a role. Therefore, this study supports the notion of a more individualised approach to micronutrient monitoring in the first 12 months after surgery, in the context of an uncomplicated post-operative course, the absence of pre-operative micronutrient deficiencies, and care including regular dietitian involvement. This approach may reduce testing costs and burden on the individual and health service, while also maintaining safety (6). Further research is recommended to investigate this further, in the short and long term.
It is acknowledged that access to multidisciplinary post-surgical support may be heterogeneous in other hospital settings (22, 23) and therefore the results of this study may not be generalisable to all surgical units. While the biochemical analysis of serum micronutrient levels were performed by more than one laboratory, and at times by more than one type of assay, this is reflective of real world practice. Clinical interpretation of results took a conservative approach with consideration of the width and lower limit of the 95% confidence intervals to determine whether the risk of micronutrient deficiency is great enough to support broad protocol driven postoperative monitoring of individual nutrients (24). Furthermore, although detailed information was collected on supplementation dose, timing of dose in relation to the biochemical micronutrient test was not recorded and may confound some nutrient results. Additionally, dietary intake was not collected to the detail required to accurately assess micronutrient intake, thus supplement intake does not reflect total overall intake of each nutrient but rather that consumed via supplements only. Understanding the contribution of food intake and meal patterns to overall micronutrient status is an important area for future research.
In conclusion, this study highlights novel relationships between bariatric surgery, micronutrient deficiencies, supplementation dose, and the presence of inflammation. Although surgery did increase the risk of micronutrient deficiency for some key nutrients in the first postoperative year, when accounting for other influencers, this is not the case for all. Therefore, this study begins to challenge the need for blanket high dose supplementation doses and testing frequencies for the 10 identified at risk nutrients in the first 12 months after surgery. A more individualised, person-centred approach may be safe and efficacious, within a supportive MDT with expertise in bariatric surgery. However, standardised blanket protocols may still be needed in other clinical settings. Future research is recommended, to investigate this concept further.