Post-bariatric biochemical abnormalities show need for closer monitoring

Micronutrient deficiencies after bariatric procedures are nuanced – differing with the type of procedure and fluctuating over time – and clinically significant, according to new research.

A five-year follow-up study of 688 patients who underwent bariatric surgery at the Singapore General Hospital has confirmed previous evidence that anaemia is the most prevalent nutritional complication.

The study found haemoglobin levels showed steady decreases after surgery although patients who had a Roux-en-Y gastric bypass (LRYGB) or one-anastomosis gastric bypass (OAGB) had a steeper decrease than patients who underwent a laparoscopic sleeve gastrectomy (LSG).

“These temporal trends indicate that surveillance and prophylactic efforts against anaemia should commence earlier for patients undergoing OAGB or LRYGB than those undergoing LSG, preferably within the first three months or even before the procedure,” the researchers said in JAMA Network Open.

Iron concentrations also fell in all patient groups but there was no significant difference between the restrictive or malabsorptive procedures.

Calcium levels were statistically higher in patients who underwent LSG procedures compared with patients who underwent OAGB or LRYGB, while intact parathyroid hormone levels were not found to differ between the patient groups.

“Since vitamin D2 and elemental calcium supplements were stipulated as part of our postbariatric treatment protocol, serum 25-hydroxyvitamin D levels were unsurprisingly higher at all points compared with baseline, and there was no statistically significant difference between patients who underwent LSG compared with those who underwent OAGB or LRYGB during follow-up,” the study authors said.

Vitamin B12 levels were numerically but not statistically significantly higher among patients who underwent OAGB or LRYGB compared with those who underwent LSG.

“Patients who underwent OAGB or LRYGB had higher serum folate (ie, vitamin B9) levels compared with patients who underwent LSG … which likely reflects the prescription of higher dosages of folate supplements by treating physicians as a countermeasure against the relatively lower hemoglobin levels in the OAGB or LRYGB group.”

Serum albumin as a marker for global nutrition status, was not significantly different between the LSG and OAGB or LRYGB groups.

“A novel finding is that among women, hemoglobin levels continued to decline in a strongly monotonic fashion during follow-up, whereas such a monotonically decreasing trend was not observed among men, thus indicating that nutritional support for women who underwent bariatric procedures was inadequate compared with support for men,” the study said.

“Furthermore, hemoglobin levels were similar despite ferritin levels being consistently higher among women who underwent OAGB or LRYGB compared with LSG. This observation may reflect an unsuccessful attempt by the treating physicians to counteract the declining hemoglobin levels by prescribing iron supplements more aggressively in women undergoing OAGB or LRYGB.”

The authors noted there was no consensus around the optimal schedule and overall length of biochemical monitoring and nutritional management after bariatric surgery.

As well as discordance between practice guidelines, there was also suboptimal adherence from surgeons.

“Future research directions include examining how prebariatric procedure energy restricted diets could entrench micronutrient deficiencies, scrutinizing whether race/ethnicity and cultural factors influence micronutrition, and more detailed longitudinal phenotyping of patients using biomarkers, such as bone mineral density and osteoclast activity,” they concluded.

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