Dietary macro- and micro-nutrients intake adequacy at 6th and 12th month post-bariatric surgery

Bariatric Surgery (BS) has recently become of great interest in treating morbid obesity and obesity-related comorbidities such as metabolic syndrome, insulin resistance, and type 2 diabetes [1‐5]. Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) are the most popular BS techniques worldwide [6, 7]. Despite the effectiveness of BS on losing weight and improving quality of life for morbid obese patients, nutritional deficiency, protein–calorie malnutrition, and muscle loss are of great concern since they may emerge due to changes in stomach volume, lack of nutrient intake, protein and solid foods intolerance, and malabsorption [8‐16]. There is limited information about dietary intake evaluation after BS based on the global recommendation [12, 17‐21]. Vanoh et al. showed that despite of supplementation the intake of vitamins E and D, also zinc and calcium did not meet reference nutrient intake (RNI) [19]. Furthermore, patients may poorly observe the recommendations regarding the regular consumption of supplements. a literature review of 15 studies on Nutritional deficiency after SG showed that, despite of supplementation the incidence of vitamin B1, B6, B12, and calcium deficiency is common due to both malabsorption and food restriction pattern [22] . In some other cases, standard supplements sometimes is not sufficient to prevent nutritional deficiency [23, 24]. The present study mainly aimed to evaluate dietary intake adequacy of wide range of macronutrients and micronutrients based on the recommended standards at 6th and 12th month after BS. Also, assessing the nutrient density and comparison of nutrient intake changes between two intervals was the next points.

Of the 58 individuals participating in the study (RYGB (N = 16) and SG (N = 42)), 71% were female and 72% were married. The patients had a mean age of 37 ± 8 years. The mean weight, BMI, WC, and HC of the participants before the surgery were 120 ± 21 (kg), 44 ± 6 (kg/m2), 130 ± 16 (cm), and 133 ± 14 (cm), respectively.

This study evaluated the dietary intake adequacy of macronutrients and a wide range of micronutrients at the 6th and 12th month after BS and assessed the changes between two intervals. The findings showed that the percentages of carbohydrate and fat intake from energy were higher than the recommendations, and the percentage of carbohydrate intake increased significantly from 6th to 12th month after BS which is in contrast to the guideline claimed that to prevent weight regain in a short-term period, 40–45 and < 20% of calories should be provided from carbohydrates and fats 1 year after the surgery, respectively [29]. Also, the nutrient density score decreased dramatically between two intervals, it seems that the patients received high calorie poor-nutrients foods. Moreover, protein intake was observed to be lower than the recommended level at both intervals. According to previous studies, for patients undergoing BS, at least 60 g/day protein is adequate and 80–90 g/day protein is needed to prevent loss of lean body mass [29, 31]. Also, Heber et al., documented that patients should consume 30 g of protein in more than one meal per day to prevent bone and muscle insufficiencies [38]. In the present study, 77.6% of the participants had a protein intake below the standard (60 g/d) at month 6, and this value increased to 89.5% 1 year after BS. The results showed that 50% of population receive 39 and 29 g protein per day at the 6th and 12th month after surgery respectively. Our findings are in line with those of Mechanick, Andreu, and Moize et al. They showed that 61, 37, and 46% of the participants had protein intake < 60 g/day 1 year after BS [12, 39, 40]. In our study, the prevalence (%) of the patients with insufficient protein intake was approximately three times as large as the one reported by Andreu et al. 12 months after surgery [39]. The low protein intake adequacy may be the result of severe food restrictions caused by the small volume of the stomach and intolerance to protein-rich foods occurring 1 year after BS [14, 15, 41]. In our study, none of the participants could consume fiber according to recommendations. Low fiber intake is probably associated with low intake of vegetables and fruits due to the mechanical restriction imposed by the surgery. This finding is similar to the finding of Novais et al. who showed that participants’ dietary fiber intake was extremely low in accordance to the AI recommendations [18]. In the present study, the dietary intake of most micronutrients could not meet the EAR value at both intervals assessments and had significant decreased from the 6th to 12th month after BS. This is in contrast with data reported by Andrue et al. showed dietary intake increased gradually through a year post- BS [26]. The nutrients with severe low dietary intake were biotin, calcium, folate, pantothenic acid, fat soluble vitamins, vitamin C, potassium and magnesium which 50% of the population received ≤35% from the minimum EAR or AI 1 year after BS and more than 95% of patients could not meet the recommendations. Moreover, 77.2 and 80.7% of subjects showed inadequacy, In terms of cobalamin and iron intake respectively. The low dietary intake of iron and vitamin B12 was in line with previous studies [26, 42]. The high inadequacy might be related to the lower tolerance to meat, fish, dairy products, egg yolk, green leafy vegetables, nuts and seeds as the main source of these micronutrients. Similar to previous studies, the median intake of vitamin C was significantly decreased 1 year after surgery, and more than 99% of the participants had a vitamin C intake below EAR at the 12th month after BS. The high inadequacy of dietary vitamin C intake was in line with the findings of the previous studies [26, 42] and might be caused by the low quality of the diet with limited fruit and vegetable intake during the surgery follow-up period. As a matter of fact, after BS, patients need to be adjusted to the change in the gastric volume and tolerance for food, especially during the first year after the surgery. Wisnewsky et al., showed patients displayed a significant 2-fold decrease in food ingestion speed after BS [17]. Moreover, changes in eating behavior after BS like vomiting, difficult to swallowing due to texture, plugging (sense of food, particularly meat and bread becoming stuck in the upper digestive tract), reported as the barriers to food intake [43, 44]. Nutrient adequacy highly depended on food choices, food texture, and speed of food ingestion, volume and frequency of meal. The texture of foods provide patients to have better ingestion and digestion. Hence, following a proper and tolerable diet containing lean meat, poultry, fish, and legume in the blended form, also, pureed form of fruits and vegetables, fruit milk shake or fruit and yogurt smoothie with wheat germ/nut powder, soup prepared with bone broth and natural vegetable extracts can help the patients receive much micronutrients, fiber, protein, complex carbohydrates, and healthy sources of essential fatty acids naturally. This can promote a healthy short and long-term post-operative dietary pattern to prevent nutritional deficiency.

Furthermore, due to the low capacity of the stomach, the patients need to take high protein -low carbohydrate ready to use formula or drink enriched with vitamins and minerals specified for these groups to promote maximum adherence to their diet, patients undergoing BS are more susceptible to protein malnutrition [45‐47], Schollenberger and Batar et al. showed that taking protein supplement can improve body composition by preventing FFM loss and enhancing loss of body fat [48, 49].

Recent studies have revealed that despite of supplementation, deficiency of cobalamin (vitamin B12), calcium, folate, fat soluble vitamins, thiamin and vitamin D is common after BS [22, 50‐52]. Bariatric surgery are also associated with the risk for neurological complications (Wernicke encephalopathy and Korsakoff-syndrome) due to both shortage in dietary intake and non-compliance of vitamin supplementation [53, 54]. Researchers have claimed that supplement therapy may not be sufficient to prevent nutrient deficiency, the reasons are: prescribed supplements may not cover all target nutrients for individuals undergoing BS, moreover, recommended dosage may be insufficient, especially for those with malabsorptive operation (RYGB) [24], and patients may not regularly take supplement. Modi et al. showed that forgetting and difficulty swallowing supplement were the two main barriers identified for patients who had undergone BS [23]. Previous studies showed, numerous bioactive foods components (Apigenin, Allicin, Genistein, Luteolin, Lycopene, Myricetin, Quercetin, Resveratrol, Vitamins) can prevent cardiovascular disease and cancer [55‐61]. These components are easily accessible in healthy foods mainly in fruits, vegetables, and whole grains [62]. Accordingly increasing the quality of their diet should be considered to promote individuals functional health. Registered dietitians are responsible to provide patients a practical dietetic recommendations according to the type of surgery and plan a proper diet based on the most common deficiencies according to the guideline like ASMBS to provide patient to meet nutrients intake from both foods and supplements [37]. Monitoring of patients in a shorter follow up period even monthly would be beneficial to provide them maximum adherence to the diet and supplements.

The main limitation of the present study was that there was insufficient data regarding the measurement of serum biochemical parameters before and after the surgery. Also, Lack of data in terms of preoperative food intake. A small sample size was another limitation of the study. Moreover, fewer Roux-En-Y patients (N = 16) than sleeve group (N = 42) was main barrier to do analyze between group. However, our study is outstanding for 1: assessing the dietary intake of a wide range of micronutrients and macronutrients according to the standards at the 6th and 12th month after BS and between two intervals. 2: evaluating nutrient density to distinguish healthy nutrient-rich foods from high-calorie and poor-nutrient foods.

According to our findings, the dietary intake of protein, fiber, and nearly all the micronutrient especially biotin, calcium, folate, pantothenic acid, fat soluble vitamins, vitamin C, potassium and magnesium was significantly lower than EAR and significantly decreased between the 6th and 12month after BS. Eating a healthy, high quality tolerable diet is more important in the short and long time after the surgery because this operation has been done forever and it is expected the patients have adherence to both diet and supplements.