Monitoring for micronutrient deficiency after bariatric surgery-what is the risk?

BACKGROUND

Bariatric surgery may increase the risk of micronutrient deficiencies; however, confounders including preoperative deficiency, supplementation and inflammation are rarely considered.

OBJECTIVE

To examine the impact of bariatric surgeries, supplementation and inflammation on micronutrient deficiency.

SETTING

Two public hospitals, Australia.

METHODS

Participants were recruited to an observational study monitoring biochemical micronutrient outcomes, supplementation dose, inflammation and glycaemic control, pre-operatively and at 1-3, 6 and 12 months after gastric bypass (GB; Roux-en-Y Gastric Bypass and Single Anastomosis Gastric Bypass; N = 66) or sleeve gastrectomy (SG; N = 144). Participant retention at 12 months was 81%.

RESULTS

Pre-operative micronutrient deficiency was common, for vitamin D (29-30%), iron (13-22%) and selenium (39% GB cohort). Supplement intake increased after surgery; however, dose was <50% of target for most nutrients. After SG, folate was vulnerable to deficiency at 6 months (OR 13 [95% CI 2, 84]; p = 0.007), with folic acid supplementation being independently associated with reduced risk. Within 1-3 months of GB, three nutrients had higher deficiency rates compared to pre-operative levels; vitamin B1 (21% vs. 6%, p < 0.01), vitamin A (21% vs. 3%, p < 0.01) and selenium (59% vs. 39%, p < 0.05). Vitamin B1 deficiency was independently associated with surgery and inflammation, selenium deficiency with improved glycaemic control after surgery and inflammation, whilst vitamin A deficiency was associated with inflammation only.

CONCLUSION

In the setting of prophylactic post-surgical micronutrient prescription, few nutrients are at risk of de novo deficiency. Although micronutrient supplementation and monitoring remains important, rationalising high-frequency biochemical testing protocols in the first year after surgery may be warranted.

Health effects associated with vegetable consumption: a Burden of Proof study

Previous research suggests a protective effect of vegetable consumption against chronic disease, but the quality of evidence underlying those findings remains uncertain. We applied a Bayesian meta-regression tool to estimate the mean risk function and quantify the quality of evidence for associations between vegetable consumption and ischemic heart disease (IHD), ischemic stroke, hemorrhagic stroke, type 2 diabetes and esophageal cancer. Increasing from no vegetable consumption to the theoretical minimum risk exposure level (306-372 g daily) was associated with a 23.2% decline (95% uncertainty interval, including between-study heterogeneity: 16.4-29.4) in ischemic stroke risk; a 22.9% (13.6-31.3) decline in IHD risk; a 15.9% (1.7-28.1) decline in hemorrhagic stroke risk; a 28.5% (-0.02-51.4) decline in esophageal cancer risk; and a 26.1% (-3.6-48.3) decline in type 2 diabetes risk. We found statistically significant protective effects of vegetable consumption for ischemic stroke (three stars), IHD (two stars), hemorrhagic stroke (two stars) and esophageal cancer (two stars). Including between-study heterogeneity, we did not detect a significant association with type 2 diabetes, corresponding to a one-star rating. Although current evidence supports increased efforts and policies to promote vegetable consumption, remaining uncertainties suggest the need for continued research.

The Burden of Proof studies: assessing the evidence of risk

Exposure to risks throughout life results in a wide variety of outcomes. Objectively judging the relative impact of these risks on personal and population health is fundamental to individual survival and societal prosperity. Existing mechanisms to quantify and rank the magnitude of these myriad effects and the uncertainty in their estimation are largely subjective, leaving room for interpretation that can fuel academic controversy and add to confusion when communicating risk. We present a new suite of meta-analyses-termed the Burden of Proof studies-designed specifically to help evaluate these methodological issues objectively and quantitatively. Through this data-driven approach that complements existing systems, including GRADE and Cochrane Reviews, we aim to aggregate evidence across multiple studies and enable a quantitative comparison of risk-outcome pairs. We introduce the burden of proof risk function (BPRF), which estimates the level of risk closest to the null hypothesis that is consistent with available data. Here we illustrate the BPRF methodology for the evaluation of four exemplar risk-outcome pairs: smoking and lung cancer, systolic blood pressure and ischemic heart disease, vegetable consumption and ischemic heart disease, and unprocessed red meat consumption and ischemic heart disease. The strength of evidence for each relationship is assessed by computing and summarizing the BPRF, and then translating the summary to a simple star rating. The Burden of Proof methodology provides a consistent way to understand, evaluate and summarize evidence of risk across different risk-outcome pairs, and informs risk analysis conducted as part of the Global Burden of Diseases, Injuries, and Risk Factors Study.