Introduction
Inflammatory bowel disease (IBD) is a chronic and relapsing inflammatory disorder of the gastrointestinal tract and includes the main subtypes Crohn’s disease (CD) and ulcerative colitis (UC). Incidence and prevalence of IBD in Western countries have been on the rise since the beginning of the twentieth century [
1]. In developing countries, an increase of IBD incidence and prevalence occurred over the last 30 years, when Westernized lifestyle and dietary habits were adopted [
2,
3]. A contribution of environmental factors to the rapid rise of IBD incidence is highly probable, considering that genetic susceptibility has been present in human beings since thousands of years without significant changes in this short period. Environmental risk factors, which affect the course of IBD are currently studied with epidemiological approaches and some influencing factors, such as breastfeeding, diet or antibiotic use have been identified [
4‐
6].
Diet is widely considered as a key environmental factor. Dietary changes affect the composition of the gut microbiome, which may influence mechanisms of immunological tolerance [
7,
8]. Western diet is mainly composed of high-sugar, low-fiber, animal-protein and fat, but low ingestion of vegetables [
9,
10]. Epidemiological data suggest, that a ‘Westernization’ of the diet may induced mucosal inflammation in susceptible individuals and may act as promoter in the pathogenesis of IBD [
11]. Recent data demonstrated a positive correlation between pro-inflammatory and ultra-processed food intake and the risk of developing IBD [
12,
13].
The reason why a dysbiosis of the intestinal microbiota promotes the development of IBD is not fully understood. A plausible explanation is the increase in potentially pathogenic bacterial species combined with a decrease in protective bacteria, resulting a disruption of local immune homeostasis, increased mucosal permeability and loss of immune tolerance [
14].
Literature data is scarce regarding the association between IBD and dietary behavior in the childhood period, considering that a subclinical intestinal inflammation can exist a long time before the outbreak of the disease [
7]. In addition, not much is known about overweight in childhood and its influence on development of IBD or disease activity. Previous work implies an association between overweight and more severe disease activity in children with IBD [
15].
Better knowledge regarding dietary habits would be of utmost importance for patients to reduce flare-ups, but also to prevent the development of IBD.
Likewise, breastfeeding and mode of delivery are considered as an important factor regarding the composition of the microbiome in the early childhood period and have been associated with the development of IBD [
16‐
18]. A review of Ananthakrishnan et al. [
19] outlined a protective effect of being breastfed for IBD. Concerning the mode of delivery as a risk factor for IBD, findings in literature are inconsistent. While various studies postulated Caesarean section (C-section) as a risk factor for IBD, a population-based study of Bernstein et al. found no association between IBD and mode of delivery [
16,
20,
21].
Physical activity levels have been associated as a protective factor regarding the risk of IBD due to a reduction of systemic inflammation [
22‐
26]. Physical activity has various effects on immunomodulatory processes and affects the balance of inflammatory and anti-inflammatory mechanisms [
27,
28]. Investigations showed that incidence of autoimmune diseases such as rheumatoid arthritis, multiple sclerosis or psoriasis is higher in patients less engaged in physical activity [
29].
According to present experience we have a lack of knowledge concerning nutrition and diet as well as physical activities among patient with IBD and their potential impact on disease development. Increased knowledge of early-life risk factors of IBD ensures better prevention of disease and may reduce the number of IBD patients.
Main goal of this study is to figure out the impact of lifestyle factors such as dietary habits, weight status and physical activity on IBD in Swiss patients, especially regarding childhood period and adolescence.
Discussion
Based on 1111 questionnaires of IBD patients we aimed to identify associations between environmental factors and the development of IBD. Our data confirm physical activity as a protective factor for IBD. Consuming meat-rich diet was associated with developing CD. On the other hand, no correlation between intake of sugar and development of IBD was observed. Overweight during childhood was associated for CD, but not for UC. Underweight during childhood and adulthood was associated with both, CD and UC/IC.
Our results support the hypothesis of a protective effect of physical activity regarding the development of IBD. Patients diagnosed with IBD reported to be less physically active during childhood and beginning of adulthood than persons from the control group. These findings are in line with the result of a review of meta-analyses recently published, that demonstrated a protective effect of physical activity regarding the development of CD [
32]. On the other hand, a Danish prospective cohort study reported no association between physical activity and risk of IBD [
33]. A possible explanation for this discrepancy to our result is, that the Danish study did not investigate the association between timing in life of physical activity and risk of IBD. The influence of physical activity on the onset of IBD is still unclear and evidence in literature is scarce. There is consensus in literature that physical activity has an impact on various aspects of the immune system and autoimmune diseases [
29]. An investigation of Steensberg et al. [
34] implied that sporting activity induces a shift in the Th1/Th2 balance to a decrease in Th1 cells. Th1 is responsible for secretion of proinflammatory cytokines as IL-1, IL-2, IL-6 and IL-8, whereas anti-inflammatory cytokines as IL-4, IL-10 and IL-13 are secreted by Th2 cells. Thus, the balance between proinflammatory and anti-inflammatory mechanisms is highly affected by the Th1/Th2 cells ratio and responsible for the types of immune responses that patients develop [
35]. Considering other diseases driven by autoimmune processes such as rheumatoid arthritis, multiple sclerosis or psoriasis, studies have shown an increased incidence in patients less engaged in physical activity [
29].
Lack of exercise may result in obesity, what is assumed to be a cause for a chronic low-grade inflammation in humans [
36]. It is explained, amongst others, by a predominance of pro-inflammatory macrophages in mesenteric visceral adipose tissue, that is responsible for secretion of various inflammatory cytokines, including IL-1 and TNF [
37]. Kugathasan et al. [
38] demonstrated that about 9–10% of children with CD and 20–34% of children with UC had an increased BMI above the 85th percentile at diagnosis. In contrary, a recently published study demonstrated no worsened disease activity 1 year after diagnosis of IBD of overweight children compared with normal weight children [
39]. Our patients with CD reported to be more often overweight compared to children of their age during childhood. Both, CD and UC patients reported to be underweighted compared to children of their age during childhood and adulthood. A recently published meta-analysis reported an positive association between underweight and the onset of CD, but not for UC [
40].
The impact of breastfeeding on the onset of IBD is also under debate. Previous trials demonstrated that alteration in the composition of the microbiota disrupts microbial mediated mechanisms of immunological tolerance [
7,
8]. Human milk contains, among others, oligosaccharides with prebiotic effects including growth of Bifidobacteria which may affect the intestinal flora and influence the risk of IBD [
41]. Our data support the assumption of a protective effect of breastfeeding, especially considering the onset of UC/IC. Furthermore, our attempt was to obtain information regarding breast milk substitution and identify bottle-feeding and frequency of sterilization of baby bottles and teats as possible risk factors for IBD. Investigations suggest a positive association of breastfeeding and development of IBD, but some controversy remains in literature [
6,
17,
42]. Unfortunately, most of patients, friends and mothers had to answer the questions in this part with ‘don’t know’, whereby the data is not conclusive. Therefore, additional investigations are warranted.
Our findings do not support the thesis that C-section enhances the risk of IBD, as more persons from the control group reported to be born via C-section. Confounders may distort the result and the findings have to be treated with caution. A population-based analysis of Bernstein reported no association of C-section and IBD [
21]. On the other hand a meta-analysis by Li et al. [
16] indicated an increased risk for CD but not for UC after Cesarean delivery.
Interestingly, significantly more patients with CD than persons from the control group reported to be born prematurely. Although perinatal mortality has been considerably reduced during the past years, prematurely born infants are still liable to a higher mortality and morbidity rate in comparison with infants born at term [
43]. These finding are in line with a work of Sonntag et al. [
44] that identified preterm birth as a risk factor for CD.
Investigations suggest that diet plays an important role in IBD. Dietary habits have been changed in the western world during recent decades and cause alterations in the composition of the gut microbiota, that may result in aberrant intestinal immune response [
45,
46]. A subclinical intestinal inflammation can be present long before occurrence of the first IBD symptoms [
7]. For this reason, it is of utmost importance to identify risk factors that affected patients before the clinically manifest disease. Our data indicate that more people from the control group consumed semi-skimmed milk (1.5% fat) during the first years of life than patients with IBD. It has been shown that high fat intakes cause an accumulation of secondary bile acids, what is responsible for reduction in growths of
Firmicutes phyla and
Bacteroidetes, both associated with IBD-like dysbiosis [
47]. On the other hand, a prospective study of Ananthakrishnan et al. [
48] indicated no association of fat consumption and IBD in women. Interestingly, patients diagnosed with CD reported to have had a milk intolerance during their first years of life, clinically characterized by diarrhea. A positive correlation between IBD and lactose intolerance is well established in literature, but evidence is scarce that a milk intolerance might be already present during the first years of life and a long time before the diagnosis of the disease [
49]. The association between sugar intake and risk of IBD remains controversial. Several studies showed a negative effect of consuming sugary food on the onset of IBD [
50‐
52]. In contrast to these findings, a large prospective study could not identify sugar intake as a risk factor for developing UC [
53]. Our data suggest no connection between IBD and eating of neither artificial nor natural sugary until the age of 18. Literature is very scarce regarding dietary habits before 18 and development of IBD. Ananthakrishnan et al. [
54] published an investigation regarding high school diet and risk of CD and UC, which demonstrated no association between intake of carbohydrates and onset of IBD.
Previous studies have shown a correlation between diet rich in animal protein and development of IBD [
55,
56]. Our data support these findings and we report that statistically significant more CD patients consume meat-rich diet in comparison to the control group. A plausible explanation is that high intake of protein result in increased production of potentially toxic bacterial metabolites, what may lead to an impaired epithelial repair process [
57]. As well, our data implicate a reduced consumption of vegetarian alimentation in IBD patients, what confirms the assumption that diets in high animal proteins lead to increased risk of IBD.
Our study has strengths as well as weaknesses. A strength is the large amount of IBD patients in our cohort with in total 1111 returned questionnaires. Furthermore, we aimed to reduce the ‘recall bias’ due to 305 returned questionnaires from patients’ mothers.
One limitation is the low overall return of questionnaires. The low response rate of the patient’s friends resulted in a small control group compared to the large number of IBD patients. Probably it was more difficult than expected for patients to reach childhood friends who grew up in a similar environment. Even though a high response rate is preferable, previous studies could demonstrate that there is no evidence of more accurate measurement in surveys with higher response rates [
58,
59].
Furthermore, we are aware that our methodology is of risk of ‘recall bias’. Even though the data of patient’s mothers reduce the ‘recall bias’, incorrect memories of behavior during childhood may exist. To confirm our findings further prospective randomised trials are needed. As well, our analyses were not matched for potential confounders. We performed a multivariate analysis included all the investigated risk factors matched for sex, age and smoking status. As there was no significant difference in the results to our published data, we decided to exclude the multivariate analysis.
In conclusion, our data demonstrate the possibility that lifestyle factors such as physical activity, dietary habits and weight status affect the onset of IBD and may play a crucial role in preventing IBD (Table
8). This study indicates that education and prevention strategies may reduce the increasing incidence of patients with inflammatory bowel disease.
Table 8
Overview of the most important findings regarding effects in regard to the development of CD and UC/IC (Statistical analyses are seen in Tables
2,
3,
4,
5,
6,
7)
Physical activity | Protective | Protective |
Breastfeeding | No significant effect | Protective |
Premature birth | Negative effect | No significant effect |
Sugar intake | No significant effect | No significant effect |
Meat-rich diet | Negative effect | No significant effect |
Vegan-/vegetarian alimentation, gluten free diet, | No conclusive data | No conclusive data |
Overweight during childhood | Negative effect | No significant effect |
Underweight during childhood and adulthood | Negative effect | Risk factor |
Acknowledgements
We wish to thank all the IBD patients, their mothers and friends for completing the questionnaires.
Members of the SIBDCS Study Group: Karim Abdelrahman, Gentiana Ademi, Patrick Aepli, Amman Thomas, Claudia Anderegg, Anca-Teodora Antonino, Eva Archanioti, Eviano Arrigoni, Diana Bakker de Jong, Bruno Balsiger, Polat Bastürk, Peter Bauerfeind, Andrea Becocci, Dominique Belli, José M. Bengoa, Luc Biedermann, Janek Binek, Mirjam Blattmann, Stephan Boehm, Tujana Boldanova, Jan Borovicka, Christian P. Braegger, Stephan Brand, Lukas Brügger, Simon Brunner, Patrick Bühr, Bernard Burnand, Sabine Burk, Emanuel Burri, Sophie Buyse, Dahlia-Thao Cao, Ove Carstens, Dominique H. Criblez, Sophie Cunningham, Fabrizia D’Angelo, Philippe de Saussure, Lukas Degen, Joakim Delarive, Christopher Doerig, Barbara Dora, Susan Drerup, Mara Egger, Ali El-Wafa, Matthias Engelmann, Jessica Ezri, Christian Felley, Markus Fliegner, Nicolas Fournier, Montserrat Fraga, Yannick Franc, Pascal Frei, Remus Frei, Michael Fried, Florian Froehlich, Raoul Ivano Furlano, Luca Garzoni, Martin Geyer, Laurent Girard, Marc Girardin, Delphine Golay, Ignaz Good, Ulrike Graf Bigler, Beat Gysi, Johannes Haarer, Marcel Halama, Janine Haldemann, Pius Heer, Benjamin Heimgartner, Beat Helbling, Peter Hengstler, Denise Herzog, Cyrill Hess, Roxane Hessler, Klaas Heyland, Thomas Hinterleitner, Claudia Hirschi, Petr Hruz, Pascal Juillerat, Carolina Khalid-de Bakker, Stephan Kayser, Céline Keller, Christina Knellwolf -Grieger, Christoph Knoblauch, Henrik Köhler, Rebekka Koller, Claudia Krieger -Grübel, Patrizia Künzler, Rachel Kusche, Frank Serge Lehmann, Andrew Macpherson, Michel H. Maillard, Michael Manz, Astrid Marot, Rémy Meier, Christa Meyenberger, Pamela Meyer, Pierre Michetti, Benjamin Misselwitz, Patrick Mosler, Christian Mottet, Christoph Müller, Beat Müllhaupt, Leilla Musso, Michaela Neagu, Cristina Nichita, Jan Niess, Andreas Nydegger, Nicole Obialo, Diana Ollo, Cassandra Oropesa, Ulrich Peter, Daniel Peternac, Laetitia Marie Petit, Valérie Pittet, Daniel Pohl, Marc Porzner, Claudia Preissler, Nadia Raschle, Ronald Rentsch, Alexandre Restellini, Sophie Restellini, Jean-Pierre Richterich, Frederic Ris, Branislav Risti, Marc Alain Ritz, Gerhard Rogler, Nina Röhrich, Jean-Benoît Rossel, Vanessa Rueger, Monica Rusticeanu, Markus Sagmeister, Gaby Saner, Bernhard Sauter, Mikael Sawatzki, Michael Scharl, Martin Schelling, Susanne Schibli, Hugo Schlauri, Dominique Schluckebier, Daniela Schmid, Sybille Schmid -Uebelhart, Jean-François Schnegg, Alain Schoepfer, Vivianne Seematter, Frank Seibold, Mariam Seirafi, Gian-Marco Semadeni, Arne Senning, Christiane Sokollik, Joachim Sommer, Johannes Spalinger, Holger Spangenberger, Philippe Stadler, Peter Staub, Dominic Staudenmann, Volker Stenz, Michael Steuerwald, Alex Straumann, Bruno Strebel, Andreas Stulz, Michael Sulz, Aurora Tatu, Michela Tempia-Caliera, Joël Thorens, Kaspar Truninger, Radu Tutuian, Patrick Urfer, Stephan Vavricka, Francesco Viani, Jürg Vögtlin, Roland Von Känel, Dominique Vouillamoz, Rachel Vulliamy, Paul Wiesel, Reiner Wiest, Stefanie Wöhrle, Samuel Zamora, Silvan Zander, Tina Wylie, Jonas Zeitz, Dorothee Zimmermann.