Introduction

More than 78 million American adults have obesity [1] (body mass index (BMI) ≥ 35 kg/m2), costing an estimated $147 billion annually due to medical care alone [2–4]. Non-Hispanic blacks and Hispanics are disproportionately affected with obesity rates of 47.8 and 42.5 %, respectively, compared to 32.6 % for non-Hispanic whites [5].

Currently, sustained long-term weight loss is most successfully obtained with bariatric surgery. Since the inception of modern weight loss surgery in 1977 with the development of the Roux-en Y gastric bypass procedure, bariatric surgeons have attempted to optimize patient care by improving techniques and post-operative care, including nutritional counseling [5]. Pre-operative nutrition, on the other hand, is largely uncultivated.

Nutritional deficiencies after surgery are commonly treated, particularly following malabsorptive procedures like the Roux-en Y gastric bypass. If deficiencies are present prior to surgery, it stands to reason that remedying them prior to surgery could be beneficial and certainly easier than after a malabsorptive procedure. Furthermore, malnutrition has been linked to adverse surgical outcomes in many studies [5].

In this study, we assessed the baseline nutritional status of our patients who were approved and scheduled to undergo Roux-en Y gastric bypass. Our aim was to determine the prevalence of micronutrient deficiencies in our patient population prior to surgery. We have focused on vitamins A, B12, D, E-α, E-β/γ, thiamine, folate, and iron as these are the micronutrient deficiencies we see most commonly in our post-operative patient population.

Methods

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Informed consent was obtained from all individual participants included in the study.

We determined the nutritional status in 58 consecutive patients in this prospective, cross-sectional study (a 20 % sample of our annual surgeries). Patients were included if they were aged 18 to 65 years and were approved to undergo the Roux-en Y gastric bypass procedure. We excluded other procedures such as adjustable gastric band and vertical sleeve gastrectomy in an attempt to limit differences within the group due to BMI and other factors that may contribute to procedure selection. While we did not exclude those taking a standard multivitamin, we excluded those taking high dose supplements such as bariatric multivitamins, which some patients choose to begin prior to surgery.

As part of the standard of care and preparation for surgery, all patients underwent routine history and physical examination. On the day of surgery in the pre-operative holding area, we collected blood specimens to determine the nutritional status of vitamins A, B12, D, E-α, E-β/γ, thiamine, folate, and iron (iron, total iron binding capacity (TIBC), and iron saturation). The α form (most biologically active form) and β/γ form (most dietary abundant form) of vitamin E were determined separately as β/γ has been shown to decrease with α supplementation [6]. High pressure liquid chromatography was used for vitamins A, E-α, and E-β/γ liquid chromatography with tandem mass spectrometry for thiamine and immunoassays for vitamins B12, D, and folate. Spectrophotometry was used for iron and turbidity for transferrin.

Statistical analysis was performed using Stata 12.1 (StataCorp, College Station, TX, USA). Missing data was treated as missing at random. We set α = 0.05 and β = 0.20 for all analysis and used two-sided tests. Descriptive univariate and bivariate analysis was utilized to describe the nutritional status and comorbidities of our patient cohort. Results are expressed as median ± standard deviation.

This research study was approved by our Institutional Review Board. All patients underwent informed consent prior to participation.

Results

This cohort was 77.6 % female and 63.8 % white (Table 1). The median age was 42.5 years (range 24 to 65 years) with no significant difference by sex or race/ethnicity. The males were heavier and taller. Median BMI was 46.3 kg/m2 (range 33.5 to 64.6 kg/m2), which varied only by race/ethnicity. Hispanics and blacks tended to present with higher BMIs than whites. Comorbidities were highly prevalent in this cohort with multiple comorbidities present in 41.4 % of patients; 54 % had hypertension, 42.0 % were diabetic, and 34.0 % had sleep apnea. The highest rate of multiple comorbidities was seen in males, which was largely driven by a higher rate of diabetes and sleep apnea.

Table 1 Pre-operative characteristics of patients presenting for bariatric surgery
Full size table

Group status for each nutrient is reported in Table 2. Median group status indicates deficiency in vitamin D in total and in all stratums. Folate and iron saturation were significantly higher in males than females. Nutritional status was poorer in blacks and Hispanics with vitamins A, D, E-α, and thiamine being significantly lower than in whites. Vitamin D was strongly correlated with BMI (p = 0.003) and age (p = 0.030). Vitamin A strongly correlated with age (p = 0.001) and number of comorbidities (p = 0.003).

Table 2 Pre-operative nutritional status of patients presenting for bariatric surgery
Full size table

To further explore the differences in this cohort, we dichotomized nutritional status into normal versus clinical deficiency (Table 3) and frank deficiency cut points (Table 4). We found significant malnutrition, particularly in vitamin D and iron. Deficiency was more prominent in blacks. Multiple micronutrient deficiency (MMND) was more common in blacks, 50.0 % versus 39.7 % overall. Number of comorbidities did not significantly correlate with MMND.

Table 3 Frequency of clinical deficiency prior to bariatric surgery by sex and race
Full size table
Table 4 Frequency of frank deficiency prior to bariatric surgery by sex and race
Full size table

Discussion

The American Society for Metabolic & Bariatric Surgery (ASMBS) reports that 80 % of bariatric surgery patients are female [5], similar to this cohort (77.6 % female). Patients are typically between the ages of 40 and 64 years of age [7–11]; our median age was 42.5 years (IQR 33 to 50 years of age). The majority of surgeries are performed on whites despite higher burden of obesity in blacks and Hispanics. We observed this as well (63.8 % white).

The highest risk of morbidity and mortality in obesity is class 3+ obesity (BMI ≥ 40 kg/m2). Class 3+ obesity was present in 81.0 % of this pre-operative bariatric surgery cohort and was more frequent in blacks and Hispanics. Multiple comorbidities were less common in class 3+ obesity (37.5 versus 63.6 % in BMI < 40 kg/m2). This is likely due to the approval process for the surgery itself. Patients with a BMI under 40 kg/m2 are considered candidates for bariatric surgery if they have “high-risk comorbid conditions such as life-threatening cardiopulmonary problems (for example, severe sleep apnea, pickwickian syndrome, or obesity-related cardiomyopathy) or uncontrolled type 2 diabetes mellitus” or “obesity-induced physical problems interfering with lifestyle (for example, joint disease treatable but for the obesity, or body size problems precluding or severely interfering with employment, family function, and ambulation)” [12–16]. Such considerations may also explain the high rate of multiple comorbidities (41.4 %) as well as for hypertension (54 %), diabetes (42.0 %), and sleep apnea (34.0 %) since these likely improve the chance a patient will be approved for bariatric surgery.

Males presented with the highest rate of multiple comorbidities, driven by a higher rate of diabetes and sleep apnea. This is despite the fact that class 3+ obesity was present in 69.2 % of males compared to 84.4 % of females. This also may be due to the approval process for bariatric surgery. It may be due to the differing motivations for males versus females. Females undergoing bariatric surgery more frequently cite physical appearance as a motivator [17, 18]. Additionally, males have a higher rate of sleep apnea largely due to greater central adiposity [19–25]. Sleep apnea also adds to the metabolic syndrome, e.g., insulin resistance, hypertension, and dyslipidemia [26].

While most comorbidities present in this cohort did not vary by race, the rate of gastroesophageal reflux disease (GERD) was significantly lower in blacks. None of the 14 blacks reported GERD, while 45.5 % of whites and 1 out of 3 Hispanics reported GERD. Caucasians are known to be at greater risk of GERD [27].

Racial disparities also exist in this cohort in nutritional status with minorities (blacks and Hispanics) having significantly lower status in vitamins A, D, E-α, and thiamine. The primary deficiency in minorities is in vitamin D, which was present in all Hispanics (n = 3) in this cohort. Slightly fewer blacks (81.3 %) presented with frank vitamin D deficiency and even fewer whites (64.9 %) fell into this category. Race is indicative of melanin concentration, and increased melanin concentration in the skin is a risk factor for vitamin D deficiency. Since melanin prevents ultraviolet (UV)-B solar radiation from photoproducing vitamin D in the skin, darker skin tones (blacks and Hispanics) are less able to photoproduce vitamin D given identical sun exposure. In addition to frank deficiency, clinical MMND was more frequent in blacks (50.0 versus 39.7 % for the cohort).

Overall, vitamin D and iron were the chief nutritional deficiencies found in pre-operative bariatric surgery patients. Vitamin D was negatively correlated with BMI (p = 0.003) and age (p = 0.030), a common finding in the literature [19–24, 28, 29]. Vitamin A negatively correlated with age (p = 0.001) and number of comorbidities (p = 0.003). Since vitamin A is an acute phase reactant, one would expect illness and chronic inflammation to correlate with vitamin A status.

The National Health and Nutrition Examination Survey (NHANES) 2003–2006 was used to develop the body iron model, which predicts that 9 % of females will have iron deficiency in the US population [28, 29]. The rate of iron deficiency in our cohort is higher than this prediction. We found 22.4 to 56.9 % deficiency in all patients. This breaks down to 26.6 to 62.2 % females and 7.7 to 38.5 % males. According to serum iron concentration, 36.2 % of our cohort are deficient, while TIBC indicates that 22.4 % are deficient. An interesting finding is that more males were deficient than females, according to serum iron concentration (38.5 versus 35.6 %).

The median vitamin D status in this cohort indicates frank deficiency as a group and in each subgroup (stratified by sex and race). According to NHANES 2005–2006 survey, the mean serum 25(OH)D in the USA is 22.4 ng/ml (56 nmol/L) [20, 24, 28–31], higher than the 16.8 ng/ml (42 nmol/L) mean in this cohort of pre-operative bariatric surgery patients. Obesity is a known risk factor for vitamin D deficiency due to an inherent need for more vitamin D to exhibit the same serum 25(OH)D concentration [5]. This greater need is due to sequestration of this fat soluble hormone in adipose tissue [32, 33]. As fat mass increases, an individual will require greater amounts of vitamin D (via photoproduction from sun exposure, dietary intake, and/or supplementation).

Limitations

Limited numbers of males and minorities, especially Hispanics, were included in this study. A larger study would be able to include more subjects from these groups, which currently undergo fewer bariatric surgeries.

Strengths

Our population is generalizable to most academic centers of excellence with the majority of patients being female and white. Our study assessed a broad range of micronutrients and identified two chief deficiencies for future study: iron and vitamin D.

Conclusions

Malnutrition in one or multiple micronutrients is pervasive in this pre-operative bariatric cohort, chiefly in vitamin D and iron. Minorities tended to have greater malnutrition. Further studies should be carried out to determine whether these deficiencies increase the risk of adverse surgical outcomes. Furthermore, the effect of pre-operative supplementation, especially vitamin D and iron, should be explored.