In this study, we found few differences in how individuals with IBS perceive the healthiness of foods compared to individuals without IBS. Food avoidance was more common in participants with IBS. Specifically, avoidance of lactose, gluten, and alcohol was more frequently reported in individuals with IBS than in those without IBS, but avoidance seemed to be driven primarily by abdominal pain. Worry and anxiety concerning the healthiness of diet were more prevalent among individuals with IBS than among those without IBS, with anxiety being especially pronounced.

Attitudes toward foods in regard to their perceived healthiness have not previously been described in patients with IBS. The results of this study show few differences between individuals with IBS and non-IBS individuals regarding the perceptions of the health aspects of food or food components, namely with white flour being the only exception. White flour is complex in the sense that it contains gluten, fructans (i.e., a FODMAP), and other wheat proteins, such as amylose trypsin inhibitors, and is low in dietary fiber [22]. Wheat products have been consistently reported to aggravate symptoms of IBS [23] and have frequently been reported as a food component that individuals with IBS avoid eating to manage their IBS symptoms [18, 24, 25]. In this study, we specifically asked if participants avoided foods because they perceived them as unhealthy and not for the sake of avoiding gastrointestinal symptoms, and nine out of ten individuals with IBS reported avoiding certain foods due to perceiving them as unhealthy. However, it remains unclear whether participants with IBS equated foods that trigger their gastrointestinal symptoms as being “unhealthy” in a broader sense. For example, a food that causes discomfort may be perceived as harmful to their overall health, even if it might conventionally be labeled as healthy for the general population. In individuals with IBS, the concept of healthiness may also be connected to the absence of adverse gastrointestinal reactions rather than solely the nutritional value.

Food avoidance is a known, but somewhat problematic, strategy among patients with IBS to manage their IBS symptoms [26]. In one study, 13.2% of patients reported severe food avoidance and restriction, and these patients had lower caloric intakes and lower intake of several micronutrients compared to patients without food avoidant behaviors [18]. In our study, participants with IBS reported avoiding gluten, lactose, white flour, and alcohol more frequently than participants without IBS. Notably, we observed a sixfold higher odds of lactose avoidance among participants with IBS, even after excluding individuals who reported being lactose intolerant. Lactose, a disaccharide and FODMAP component, is known to exacerbate symptoms in many individuals, particularly those with IBS [27]. The reason why individuals who do not perceive themselves as lactose intolerant still avoid lactose remains unclear, though a combination of psychological factors and adverse reactions to dairy products is likely involved [28]. However, we did not observe differences in dairy product avoidance between participants with and without IBS, which may be due to the increased availability of lactose-free dairy products in Sweden over the past decade.

Alcohol was also reported as avoided more frequently by the IBS group, and this corresponds well with previous research that has shown that alcohol or alcoholic beverages are commonly avoided by individuals with IBS [29]. In a study of Swedish adults with IBS, 31% of IBS patients avoided wine and beer [17]. However, after adjusting for abdominal pain, we no longer observed that IBS itself was a significant determinant of food avoidance. Abdominal pain is a key feature of IBS but was also commonly reported in our study population among individuals without IBS. Having abdominal pain, regardless of IBS, seems to be driving avoidance of certain foods.

In other studies of food avoidance in individuals with IBS, commonly reported avoided foods or food components include dairy products, legumes, apple, white flour, gluten-containing foods, spicy foods, and high-fat foods [17, 30]. Here, we did not note any significant avoidance of fat. This may reflect the spirit of the time when the survey was conducted, as high-fat diets, often abundant in dairy products, had been popular in Sweden for a period of time and thus might not have been perceived as unhealthy.

Anxiety and depression are known to be more prevalent in IBS patients than in the general population [11]. The increased risk of anxiety or depression is, however, also increased among individuals with functional abdominal pain without fulfilling requirements for IBS diagnosis [31]. Anxiety in general, as well as GI-specific anxiety (worry and/or awareness of abdominal discomfort), has been associated with more severe IBS symptoms [17]. In this study, we also showed that patients with IBS felt more worried and anxious in regards to the healthiness of their diet compared to non-IBS individuals. This might pose an additional burden on the patients and could potentially lead to even more severe food avoidance. However, due to the small number of participants, we could not assess whether individuals who felt worried about the healthiness of their diet had an increased risk of food avoidance.

The methodological strengths of this study include the random selection of participants, a fairly high response rate for a postal survey [32, 33], and a high completion rate among respondents. However, as with all dietary studies, there may have been a selection bias, as individuals with a greater interest in health and diet may have been more likely to respond, which may limit the generalizability of the results. In addition, there was a slight overrepresentation of women among the respondents and a somewhat higher proportion of individuals with higher education compared to the general Swedish population, which should be considered when interpreting the results. The study only included individuals aged 20–65 years. However, that does not reduce external validity, since IBS is less common outside of this age range [34].

A limitation in this study is the somewhat small sample size of participants included with IBS, reducing the power to detect true differences between the groups and preventing further sensitivity analyses. A more balanced sample size between participants with and without IBS would have been optimal. Additionally, the diagnosis of IBS was self-reported and, due to the nature of the survey, could not be confirmed by a physician [35]. However, the proportion of individuals reporting IBS closely matched the expected prevalence rate, which enhances the credibility of these reports [3]. Furthermore, we strengthened the validity of the self-reported diagnosis by including a control question about the presence of frequent abdominal pain and/or discomfort, further supporting the accuracy of the IBS diagnosis. Optimally we would have included all diagnostic criteria for IBS in the questionnaire, but since we had to restrict the number of questions included, this was not possible. Moreover, all foods and food components assessed in this study were predefined, which may have left out foods of importance.