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Assessing zinc serum levels and prescribing zinc supplements is recommended before and after surgery

Assessing zinc serum levels and prescribing zinc supplements before bariatric surgery to alleviate the prevalence of zinc deficiency after the operation is recommended for all patients, according to researchers Iran University of Medical Sciences, Tehran, Iran, who reported a high prevalence of preoperative zinc deficiency among morbidly obese patients who underwent bariatric surgery at their centre. The findings were published in the study, ‘The prevalence of zinc deficiency in morbidly obese patients before and after different types of bariatric surgery’, published in BMC Endocrine Disorders.

The authors stated that zinc serum levels are reduced in patients with obesity, indicating the correlation of zinc deficiency and obesity-related complications such as insulin resistance. In addition, serum zinc levels are the main pool of available zinc in the human body, and zinc deficiency can cause hair loss, diarrhoea, glossitis, nail dystrophy, hypogonadisms in males, infertility and anaemia, delayed wound healing, skin lesion and taste alteration.

The authors noted that previous studies have reported that zinc deficiency in patients with obesity can be explained by:

  • The chronic inflammation in patients with obesity promotes metallothionein and zinc-copper transporter expression, resulting in the accumulation of the metal in hepatocytes and adipocytes, responsible for decreased zinc serum levels; and

  • Inadequate intake of zinc resources with high concentrations of this micronutrient might account for zinc deficiency

To assess the zinc deficiency in patients with morbid obesity after mini-gastric bypass, Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG), and its changes according to the types of surgical procedures among the Iranian population.

This study aimed to assess the zinc deficiency in morbidly obese patients after bariatric surgeries and its changes according to the types of surgical procedures among the Iranian population, they conducted a retrospective cohort study at the obesity centre of Rasoul Akram Hospital, Tehran, Iran, from December 2018 to December 2019.

In total, 413 patients (body mass index (BMI) ≥ 40kg/m2 or BMI ≥ 35 kg/m2 with a complication or risk factor) who underwent bariatric surgery were included in the study and assigned one of three groups according to the type of bariatric surgery (mini-gastric bypass, RYGB, and SG). The collected zinc serum levels during the preoperative period and follow-up measurements at three, six and 12 months after the surgery. Baseline clinical and demographic features were also recorded on a checklist, and the reference value for zinc serum levels was 70-120μg/dl.

At the first postoperative visit (two to three weeks after the operation), patients were encouraged to take multivitamin and mineral supplementations postoperatively (one tablet orally daily), which contained 30mg zinc as zinc oxide per tablet alongside other vitamins and micronutrients.


The 413 patients had a mean age of 40.57 ± 10.63 years and a mean preoperative BMI of 45.78±6.02kg/m2. There were more female patients (334, 83.3%) and more underwent mini-gastric bypass than RYGB or SG (n=289, n=94 and n=30, respectively). The ANOVA test for age between surgical groups was not significant (p=0.413) and hyperlipidaemia was reported as the most common comorbidity in all patients (188/413).

The mean preoperative zinc plasma concentration was 89.96±21.4μg/dl. The zinc serum level after surgery was significantly decreased in patients (p< 0.001), with statistically significant differences between the preoperative period and the six and 12 months after the operation, as well as between the third postoperative month and the six and 12 months after the operation. There was an association between BMI groups and zinc serum levels (p=0.044), with a statistical difference between 40≤ BMI≤ 50 and BMI> 50 groups. Furthermore, the association between sex and zinc serum levels was significant (p=0.038). There was no association between zinc serum levels and any comorbidities. However, there was a significant association between impaired fasting blood sugar, type 2 diabetes and zinc deficiency, p=0.027 and 0.047, respectively).

At 12 months after surgery, the zinc serum level was significantly lower in the mini-gastric bypass compared to the other types of surgeries: 27.7% of the patients who underwent mini-gastric bypass, 29.8% of RYGB and 13.3% of SG experienced zinc deficiency. However, no significant difference in zinc deficiency between different types of surgery was observed.

The researchers also noted that compared to the male gender, higher rates of zinc deficiency in females could be attributed to different food patterns.

“To track the exact changes in the prevalence of zinc deficiency among different types of bariatric surgeries during the pre- and postoperative period, we suggest further prospective studies with long-term follow-ups, assigning a similar number of patients into each group of surgery and matching study participants regarding nutritional habits, monitoring the patients to receive their multivitamin and micronutrient supplementations regularly after the operation, and evaluating the albumin and CRP serum levels as potential confounders,” the authors concluded.

Further reading

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