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Adv Biomed Res 2023,  12:211

The Effect of Laparoscopic Sleeve Gastrectomy on Serum Levels of Vitamin A, D and B12 and Iron Profile on Patients with Morbid Obesity

1 Department of Surgery, Loghman Hakim University Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran
2 Student Research Committee, School of Medicine, Isfahan, Iran, University of Medical Sciences, Isfahan, Iran
3 Student Research Committee, School of Medicine, Isfahan, Iran, University of Medical Sciences; Isfahan Minimally Invasive and Obesity Surgery Research Center, Alzahra University Hospital, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran

Date of Submission21-May-2022
Date of Acceptance20-Jul-2022
Date of Web Publication31-Aug-2023

Correspondence Address:
Amir Hossein Irajpour
Loghman Hakim University Hospital, Makhsoos St., South Karegar Ave, Tehran
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/abr.abr_166_22

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Background: One of the concerns after bariatric surgery is the lack of nutrients and vitamins due to anatomical and physiological changes that occur after the surgery. The aim of the present study is to evaluate the effect of laparoscopic sleeve gastrectomy on these nutrients and vitamins.
Materials and Methods: This prospective study was performed in Tehran and all the patients who met the inclusion criteria before the surgery were tested for serum levels of vitamins A, B12, D, ferritin, serum iron, and TIBC. The patients were tested once again for the same micronutrients, one year after surgery.
Results: A total of 120 patients had the inclusion criteria and all of them completed the follow-up period. Of the patients, 64.2% (77 patients) were female and 35.8% (43 patients) were male. The mean weight of the patients was 122.1 ± 14.8 kg and the mean BMI of patients before surgery was 43.6 ± 4.4 kg/m2. Comparing these parameters before and after surgery showed that serum levels of vitamins A and B12, ferritin, and TIBC were not significantly different from before surgery. However, vitamin D levels after surgery were significantly higher than before (p < 0.001).
Conclusion: The result of the present study demonstrated that laparoscopic sleeve gastrectomy is one of the most effective surgical methods for obesity treatment and does not cause a lack of nutrients and vitamins in long term and does not require supplementation. In addition, it promotes serum levels of vitamin D, which is effective in preventing the effects of vitamin D deficiency in obese patients.

Keywords: Bariatric surgery, nutrients, obesity, vitamins

How to cite this article:
Rashnoo F, Seifinezhad A, Zefreh H, Sheikhbahaei E, Irajpour AH. The Effect of Laparoscopic Sleeve Gastrectomy on Serum Levels of Vitamin A, D and B12 and Iron Profile on Patients with Morbid Obesity. Adv Biomed Res 2023;12:211

How to cite this URL:
Rashnoo F, Seifinezhad A, Zefreh H, Sheikhbahaei E, Irajpour AH. The Effect of Laparoscopic Sleeve Gastrectomy on Serum Levels of Vitamin A, D and B12 and Iron Profile on Patients with Morbid Obesity. Adv Biomed Res [serial online] 2023 [cited 2023 Sep 26];12:211. Available from:

  Introduction Top

For over two decades, obesity has been recognized as a global health problem[1] and continues to be among major health problems due to its being an important risk factor for chronic diseases such as type 2 diabetes mellitus (T2DM), cardiovascular diseases (CVD), chronic kidney disease (CKD), non-alcoholic fatty liver disease (NAFLD), and many more.[2],[3]

As time goes by, the number of obese patients with co-existing obesity-related comorbidities is rising.[4],[5] According to the 2017 global nutrition report, 2 billion adults and 41 million children are either obese or overweight worldwide.[6] It was proposed that the prevalence of obesity and overweight levels will rise to 89% in males and 85% in females by the year 2030.[7] According to Vaisi-Raygani et al., 21.4% of elder adults in Iran are obese,[8] and the overall prevalence of obesity in Iran is estimated to be 12.1%.[9]

Due to the high prevalence of obesity and its diverse complications, various surgical -also known as bariatric surgery- and non-surgical methods have been proposed to treat obesity in adults. Non-surgical weight loss methods include lifestyle changes (diet and exercise)[10],[11] and medications.[12] Bariatric surgery (BS) is the most effective treatment method for morbid obesity, which can lead to sustained weight loss and improvement of obesity-related comorbidities.[13],[14],[15],[16]

Roux-en-Y gastric bypass (RYGB) and Sleeve Gastrectomy (SG) are the most frequently applied techniques of BS.[17],[18] SG has gained more popularity over the past decade as a feasible and safe technique due to its simplicity, better comorbidity resolution rates, and outstanding short-term weight loss outcomes.[12],[19],[20]

Despite all its benefits, BS causes some complications. Among which is the recurrence of obesity and its comorbidities and nutritional deficiencies caused by the reduction of bioavailability and digestion.[16] However, these deficiencies are highly prevalent among obese patients before BS.[21] The most common nutritional deficiencies among obese patients prior to BS are, Vitamin B12, folic acid, calcium, and thiamine.[22]

In the article published by Hosseini-Esfahani et al.[23] in 2020, regarding nutrition deficiencies of patients undergoing BS in a 1-year follow-up in Tehran, there were significant differences in serum levels of albumin, calcium, vitamin B12, and 25-hydroxyvitamin D (25-HVD) pre and post-operatively.

According to Mulita et al.,[24] one year after BS, there was an increase in ferritin, magnesium, and vitamin B12 deficiencies. However, there was no significant difference between iron, folic acid, and phosphorus deficiencies pre and post-operatively.

Saif et al.[25] reported that there was no significant difference in ferritin, iron, total iron binding capacity (TIBC), calcium, magnesium, phosphorus, and zinc before and after laparoscopic sleeve gastrectomy (LSG).

This study was performed due to the increasing prevalence of obesity and overweight and the requests for these surgeries by patients, as well as the limited studies conducted in the country on the prevalence of nutrient deficiencies after LSG.

  Materials and Methods Top

This cross-sectional study was performed without a control group over a period of one year. All patients referred to Loghman-Hakim Hospital in Tehran diagnosed with severe obesity, which made them a candidate for LSG were evaluated for this study. Inclusion criteria were patients with a BMI >40 kg/m2 and without obesity-associated medical diseases (i.e. type 2 diabetes mellitus (T2DM) and/or hypertension (HTN)) or patients with a BMI >35 kg/m2 with one of the obesity's comorbidities (e.g., T2DM, heart disease, HTN, and obstructive sleep apnea). After receiving the code of ethics from the research committee of Shahid Beheshti University of Medical Sciences and obtaining the consent of patients to enter the study, demographic data including age, weight, sex, and BMI were recorded. Blood samples were evaluated for serum levels of vitamins A, D, B12, ferritin, and TIBC. All the lab data were analyzed by the same laboratory team in our surgical center.

Patients who had previously undergone other non-surgical treatments for obesity or had non-obesity-related underlying conditions were not included. Then, all patients underwent standard LSG and received a multi-vitamin supplement for 6 months (Pharmaton, one capsule daily, and Calcium citrate). The patients' post-operative diet was prescribed by an expert nutritionist according to a protocol for sleeve gastrectomy patients. At the sixth month visit, patients were asked to discontinue multi-vitamin supplementation. One year after reoperation, the patient's BMI was recorded. In the next step, blood samples were sent to check the serum levels of vitamins A, D, B12, ferritin, and TIBC, and the results were recorded.

The obtained data were entered into the Statistical Package for Social Sciences (SPSS) (version 24, SPSS Inc., Chicago, IL). Quantitative data were reported as mean ± standard deviation and qualitative data as frequency distribution (percentage). Independent t-tests and Chi-square were used to analyze the data. P value < 0.05 was considered a significant threshold.

  Results Top

During the study period, 120 patients who met the inclusion criteria were enrolled in the study. All patients completed the follow-up period. The demographic characteristics of the patients are shown in [Table 1]. Of these, 64.2% (77 patients) were female and 35.8% (43 patients) were male. The mean age of patients was 35.4 ± 8.3 years. The mean height of patients was 163 ± 9.9 cm and the mean weight of patients was 122.1 ± 14.8 kg and the mean BMI of patients before surgery was 43.6 ± 4.4 kg/m2 [Figure 1], [Table 1]. The mean serum parameters of patients before surgery included vitamin A: 17.7 ± 9.2 (μg/dl), vitamin D: 25.6 ± 8.1 (ng/ml), vitamin B12: 413.7 ± 247.3 (pg/ml), ferritin: 67.1 ± 8.63 (ng/ml) and TIBC: 342.4 ± 65 (μg/dl). After surgery and at a visit one year later, BMI was 30.8 ± 1.4 (kg/m2) [Table 2]. Mean serum indices of patients after surgery included vitamin A: 16.9 ± 2.8 (μg/dl), vitamin D: 30.4 ± 11.2 (ng/ml), vitamin B12: 405.1 ± 4.236 (pg/ml), ferritin: 67.7 ± 9.69 (ng/ml), and TIBC: 340.5 ± 64.2 (μg/dl). A comparison of parameters before and after surgery showed that serum changes in vitamins A, B12, ferritin, and TIBC were not significantly different from before surgery, indicating that long-term laparoscopic sleeve gastrectomy did not alter serum levels of these micronutrients. Serum vitamin D showed a significant difference before and after surgery (P < 0.001) [Table 2].
Figure 1: Comparison of classified body mass index before and after surgery

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Table 1: Characteristics of the study population

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Table 2: Comparison of nutritional and biochemical parameters before and after surgery in patients

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  Discussion Top

Obesity is one of the pervasive global problems that is rapidly increasing with the change from a traditional lifestyle to machine life, which has increased with the occurrence of problems related to obesity and mortality.[25] Bariatric surgery is accepted as the most effective treatment for obesity. LSG and RYGB are two standard and advanced methods of BS. Nowadays, LSG is more desired due to its easier operation technique and fewer complications than RYGB.[26]According to studies, deficiency of nutrients and vitamins due to anatomical changes in the mechanisms of absorption in the gastrointestinal tract is one of the most common and serious long-term complications for patients undergoing bariatric surgery.[27] It was mentioned earlier that LSG only limits the volume of the stomach and does not affect food absorption in the gastrointestinal tract, but RYGB and other malabsorptive methods, change the physiological pathways of the gastrointestinal tract and have a higher risk of nutrient deficiency. In LSG, a large part of the body and fundus of the stomach is removed. These parts of the stomach contain peritoneal cells and main cells that secrete gastric acid and endogenous factors that play a major role in the absorption of vitamin B12 and calcium. This principle may suggest that laparoscopic sleeve gastrectomy causes a deficiency of vitamin B12 and calcium in the body in long term.[28] In the study of Mulita et al.,[24] it was shown that one year after SG, 15% of the study population had vitamin B12 deficiency. In contrast, there was no difference between vitamin B12 levels before and after LSGin our study. Despite removing most of the antrum in LSG, we found no change in vitamin B12 deficiency after LSG. This could be due to the compensating mechanisms of the GI tract, and the fact that after LSG, patients eat smaller but more frequent meals – the result of limited stomach volume– which will result in the secreted intrinsic factor being in proportion to food intake. The prevalence of vitamin B12 deficiency in malabsorptive BS methods is higher than in volume-limiting ones, thus regular administration of vitamin B12 after these surgeries is strongly recommended.[29] However, in the case of gastric volume-limiting surgeries, there is no conclusive evidence that this vitamin should be administered regularly, which shows that these surgeries may not cause a deficiency of this vitamin.[30] The results of our study also testified to this.

Decreased stomach volume, nausea and vomiting after surgery, and reduced food intake can cause other micronutrient deficiencies. Iron deficiency anemia is the most common anemia in patients after BS. Some studies have shown that the prevalence of this anemia can be up to 17% after surgery.[31] A decrease in serum ferritin is a more specific marker than a decrease in serum iron in the diagnosis of anemia. Studies have shown that up to 30% of patients experience a decrease in serum ferritin 5 years after BS.[32] In our study, after one year, no decrease in serum ferritin was observed, which could be due to the difference in the follow-up period of patients, as well as the administered multivitamin supplement. The primary aim of this study was to evaluate the effect of LSG on changes in serum levels of some micronutrients. The results of the present study showed that after one year of surgery, no significant decrease in serum levels of vitamin A, vitamin D, vitamin B12, ferritin, and TIBC was observed. This could be due to the fact that LSG is a volume-limiting procedure and does not affect nutrient absorption. However, it has been proven that some malabsorptive BS methods, cause deficiencies in vitamins and micronutrients causing many complications and problems in patients.[33] The results of this study can be important evidence that LSG is not only a surgical procedure with fewer early complications but also does not change the serum levels of micronutrients and vitamins in the long run.

Vitamin D is one of the most important vitamins in the body for calcium homeostasis and bone structure. Patients with obesity may have vitamin D deficiency for several reasons, including the accumulation of this vitamin in adipose tissue, decreased physical activity, and consequently lack of exposure to sunlight- which plays a key role in the construction of this vitamin in the body - and the psychological effects of obesity (that patients tend to cover their bodies from others, and as a result, being less exposed to the sun).[34] With surgery and weight loss and elimination of the problems mentioned above, serum levels of this vitamin in patients may increase and therefore problems such as osteoporosis in these patients may decrease. Our study showed a statistically significant increase in serum levels of vitamin D in patients one year after LSG. The study by Kull et al.[35] also showed that patients with obesity had lower levels of vitamin D before surgery which was consistent with the results of the present study. Vitamin A is a fat-soluble vitamin that plays an important role in metabolism and especially vision in the human body. Various studies have examined the deficiency of this vitamin after BS. In a study by Jalilvand et al., the prevalence of this vitamin deficiency after LSG is 12% while in our study there was no significant decrease in serum levels of this vitamin after LSG.[36] This difference may be explained by the fact that, unlike our study, there was a high vitamin A deficiency in the study population of Jalilvand's study, and vitamin A deficiency found after the intervention was not caused by the intervention itself.

  Conclusion Top

Currently, the results of various studies around the world on the necessity of treatments with nutrient and vitamin supplements after LSG are different, and there is no single guideline for prescribing or not prescribing these supplements. The results of the present study showed that laparoscopic sleeve gastrectomy is one of the most effective surgical methods that does not cause a lack of nutrients and vitamins in the long run and does not require complementary therapies which sometimes impose exorbitant costs for patients.

Ethics approval and consent to participate

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.

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  [Figure 1]

  [Table 1], [Table 2]


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