Irritable bowel syndrome (IBS) is a prevalent abnormality characterized by abdominal pain and altered bowel habits (Thompson
et al., 1999). Health–related quality of life (HRQOL) is impaired in IBS. It causes reduced work performance among IBS (Varni
et al., 2006). The prevalence of IBS among children was estimated at approximately 2-24% globally and its prevalence among Asian children ranged from 2.8-25.7% (Devanarayana
et al., 2015). A systematic review investigated the epidemiology of IBS in Iran and revealed that the IBS prevalence was from 1.1% to 25% (Jahangiri
et al., 2012). The global prevalence of IBS in adolescents varied widely from 25.7% in Korea (Son
et al., 2009), 19.89% in China (Zhou
et al., 2011), and 4.8% in Colombia (Lu
et al., 2016). Overall, in western countries, IBS symptoms was present in 22% to 45% of children between the ages of 4 to 18 years (Rasquin
et al., 2006). It was also reported that the prevalence of IBS was 1.8 times higher in girls compared to boys (Dong
et al., 2005).
Since the etiology of IBS has been unknown, several theories were proposed including: altered gut microbiota function, immunological abnormality, food allergy, changed GI motility, psychological factors, and genetic predisposition (Drossman, 1999). Although it has been previously suggested that diet played an important role in developing IBS (Eswaran
et al., 2011, Fedewa and Rao, 2014, Shepherd
et al., 2008), little is known about eating habits in adolescent IBS patients; this is a common age at which eating disorders will be developed. The relationship of IBS with foods or nutrients was previously assessed by several studies particularly among adults (Khayyatzadeh
et al., 2016). With regard to the synergistic effects of foods on each other and the large variety of foods associated with IBS (Khayyatzadeh
et al., 2016), investigating dietary patterns and IBS might be necessary among children and adolescents. Approximately 75% of patients with IBS reported a relationship between specific food ingestion and IBS symptoms (Monsbakken
et al., 2006, Simren
et al., 2001), especially fatty and starchy foods (Shepherd
et al., 2008, Staudacher
et al., 2011). Furthermore, different food ingredients were suggested to stimulate IBS symptoms, which included lactose, fructose, wheat, and caffeine. On the other hand, recent studies have shown that dietary manipulation, including a diet low in fermentable carbohydrates, can be beneficial in patients with IBS. The dietary habits of this group of functional gastrointestinal disease patients should be recognized before any dietary alternation (Ross
et al., 2016). Since individuals' dietary patterns are different around the world, investigating the association between adherences to major dietary patterns and health outcomes is important. Individuals in different parts of the world have various culture, beliefs, and geography, which can influence dietary patterns. Considering the few number of studies over the association between dietary patterns and IBS, limited data are available about the association between major dietary patterns and gastrointestinal health in all age groups especially among adolescents (Monsbakken
et al., 2006, Simren
et al., 2001). Therefore, the current study aimed to investigate the association between major dietary patterns and IBS within a sample of Iranian adolescent girls.
Materials and Method
Study population: The present cross-sectional study was conducted in 2015 with the aim of assessing the relationship between IBS and dietary patterns among 750 adolescent girls in Mashhad city and Sabzevar city, northeastern of Iran. All participants were 12-18 year-old students. The selected study population was recruited using a random cluster sampling method from 20 schools in five areas of Mashhad city and 5 schools in two areas of Sabzevar city. The participants had no history of chronic diseases (colitis, diabetes, cardiovascular diseases, cancer, and hepatitis).
Dietary assessment: In order to collect dietary information, a 168-item food frequency questionnaire (FFQ) was developed for the Tehran Lipid and Glucose Study. The validity and reliability of this FFQ were reported in a previous study (Hosseini Esfahani
et al., 2010). The FFQ has nine multiple-choice frequency response categories varying from “never or <1/mo” to “_12/d”. Daily nutrient intakes for each participant were calculated using the US Department of Agriculture’s (USDA) national nutrient databank (Pehrsson
et al., 2000). In order to minimize the influence of under- and over-reporting of energy intakes, we omitted the participants whose reported total energy intakes were not within the range of 800 to 4200 kcal/day (Azadbakht
et al., 2005) (n = 80). As a result, data from 670 student girls were finally included in the statistical analysis. To identify dietary patterns, we determined 40 predefined food groups (
Table 1). Certain food groups were created based on the similarity of nutrients and their association with IBS.
Assessment of IBS: We used a version of Rome III questionnaire translated into Persian, as a part of the original questionnaire in order to assess the participants' Functional gastrointestinal disorders (FIGDs). The validation of this questionnaire was reported in a previous study (Sorouri
et al., 2010). According to the Rome III criteria, IBS is characterized by: Recurrent abdominal pain or discomfort at least 3 days/month in the last 6 months associated with two or more of the following: Improvement with defecation, onset associated with a change in frequency of stool, and onset associated with a change in form (appearance) of stool.
Assessment of other variables: General demographic information including age, smoking status, menstruation status, medical history, and drug use was obtained by expert interviewers. Anthropometric parameters were measured by standard protocols. Weight was measured while participants were minimally clothed and not wearing shoes. Height was measured using a tape measure while the individuals were standing and not wearing shoes. Body mass index (BMI) was calculated as weight (in kg) divided by height squared (in meters). Dietary habits including regular meal pattern, chewing sufficiency, fluid consumption, and breakfast consumption were assessed by pretested questionnaire.
Data analysis: Principal component analysis was used to identify the major dietary patterns based on the 40 food groups and factors rotated by varimax rotation. We determined three factors with regard to Eigen values > 1.5 and interpretation of scree plot. Therefore, three major dietary patterns were diagnosed and then labeled based on our interpretation of the data and of the previous studies. For all participants, factor scores of each derived pattern were obtained by summing intakes of foods weighed by their factor loadings. We categorized individuals by quartiles of dietary pattern scores. We used one-way analysis of variance to examine the significant differences in continuous variables (age, weight, BMI) across quartile categories of dietary pattern scores. In addition, chi-squared test was performed for assessing the categorical variables (passive smoker, menstruation, regular meal pattern, chewing insufficiency, fluid consumption, and breakfast consumption) across quartiles of dietary pattern in participants. Energy-adjusted intakes of foods and nutrients were examined by covariance analyses across quartiles of dietary patterns. Logistic regression in various models was also applied to investigate the relationship between dietary patterns and IBS. In the first model, we controlled the confounding variables of age and energy. In the second model, further adjustments were done for passive smoking, BMI, and menstruation. Additional adjustments were also performed for regular meal pattern, chewing sufficiency, breakfast consumption, and fluid consumption. We examined overall trends for the odds ratios by increasing quartiles of the dietary patterns scores using Mantel- Haenszel extension. A P-value < 0.05 was defined as statistically significant. All statistical analyses were performed using SPSS version 15.0 (SPSS Inc, Chicago, IL, USA).
Ethical considerations: Written informed consent forms were filled by all individuals before beginning of the study. This study was approved by the Ethics Committee of Mashhad and Sabzevar Universites of Medical Sciences.
Results
Identified major dietary patterns: After performing factor analysis, three different dietary patterns of healthy, mix, and western were determined in our sample population to identify the food patterns. In healthy dietary patterns, intakes of all kinds of vegetables, tomatoes, garlic, fruits, olives, egg, yoghurt, and legumes were higher than other patterns. The mix dietary pattern contained high intakes of potatoes, hydrogenated fats, vegetables oil, sugar, salt, spices, and tea. Western dietary pattern was high in intakes of refined grains, snacks, red meat, poultry, fish, organ meat, pizza, fruits, fruit juice, industrial juice and compote, mayonnaises, nuts, soft drinks, sweets, and deserts. The factor-loading matrixes for three dietary patterns are presented in
Table 2.
General characteristics and dietary habits of study participants: General characteristics and dietary habits of the study participants across quartiles of the dietary pattern scores are presented in Table 3. No significant differences were observed between the participants' age, weight, menstruation status, and regular meal pattern across all quartiles. However, participants in the healthy dietary pattern group were more likely to be passive smokers in the lowest quartile compared to the highest quartile (
P = 0.01). Furthermore, in the lowest quartile of this pattern, participants consumed more fluids than the highest quartile (
P = 0.003), although in the highest quartile of the healthy pattern individuals consumed breakfast more regularly than those in the lowest quartile (
P = 0.02). In addition, BMI was higher in the mix pattern than the lowest quartile in comparison with the highest quartile (
P = 0.03). In the western pattern category, fluid consumption was higher among those in the highest quartile compared to the lowest one (
P = 0.04). Age and energy-adjusted intakes of food groups and nutrients across quartile categories of dietary pattern scores are shown in
Table 4. Red meat, low and high fat dairies, fruits, legumes, coffee, and spices were more eaten by participants in the fourth quartile of the healthy dietary pattern in comparison to those in the first quartile. Energy, protein, total carbohydrates, total fiber, sucrose, fat, total SFAs, total MUFAs, total PUFAs, cholesterol, vitamin C, vitamin E, and vitamin A were consumed more frequently in participants of the highest quartile of healthy dietary pattern compared to those in the lowest quartile. However, refined grain was consumed less by participants of the highest quartile of healthy pattern than compared with the individuals in the lowest quartile. In comparison to the participants in the first quartile of the mix dietary pattern, vegetable oil, spices, nuts, and salt were consumed more frequently by those in the fourth quartile. Similarly, significant differences were observed between the lowest and highest quartiles regarding intake of energy, total carbohydrates, total fiber, sucrose, fat, total MUFAs, total PUFAs, vitamin C, and vitamin E. Individuals in the highest quartile of western dietary pattern consumed more red meat, processed meat, high fat dairy, fruits, legumes, coffee, refined grain, and nuts compared to the participants in the lowest quartile. Similarly, consumption of energy, protein, total carbohydrates, total fiber, sucrose, fat, total SFAs, total MUFAs, total PUFAs, cholesterol, vitamin C, vitamin E, and vitamin A were significantly higher among participants of the fourth quartile of western dietary pattern in comparison to the first quartile.
The relationship between major habitual dietary patterns and IBS in whole population: Ultivariable-adjusted odds ratio (OR) for IBS across quartiles of the dietary pattern scores are presented in Table 5. No significant association was observed between dietary pattern scores and IBS using crude or adjusted models. Individuals in the fourth quartile of the healthy dietary patterns had less OR for IBS (OR: 0.83; 95% CI: 0.47-1.48) than those in the first quartile, although this correlation was not significant. Compliance with the mix and western dietary patterns increased the risk of IBS by 42% (OR: 1.42; 95%CI; 0.83-2.43) and 22% (OR: 1.22; 95%CI; 0.71-2.1) in participants at the highest and lowest quartiles, respectively; although these correlations were not statistically significant. After adjusting for the potential confounders (model1, model 2, and model 3), individuals in the healthy dietary pattern group had a lower, but a non-significant OR for IBS, in contrast to the participants of the mix and western dietary patterns.