The role of the Dutch dietary and physical activity guidelines in inflammatory bowel disease: Implications for clinical practice

Inflammatory bowel disease (IBD) is a chronic inflammatory disorder of the gastrointestinal tract of which Crohn’s disease (CD) and ulcerative colitis (UC) are the main subtypes. Both are characterized by a variable and unpredictable disease course with periods of active disease alternating with periods of remission. The pathogenesis of IBD seems to be a complex interaction between the gut microbiota, immune system, genetics and environmental factors like diet and physical activity. Besides the likely contribution to the development of IBD, diet and physical activity also significantly impact the disease course and clinical outcomes in patients with established IBD. However, evidence-based guidelines in clinical IBD practice are lacking, which hampers the guidance of IBD patients who are interested in diet and physical activity as part of their treatment. All currently available evidence regarding beneficial effects of nutrients and physical activity in IBD is in line with the Dutch guidelines for a healthy diet and physical activity. However, these guidelines as a whole have not been investigated in IBD yet. Therefore, the aim of this thesis was to investigate the health effects of the Dutch dietary and physical activity guidelines as part of treatment in IBD patients.

First, we used an online survey to investigate associations between the habitual diet of IBD patients and disease activity. The Dietary Inflammatory Index (DII) was used to determine the inflammatory potential of the diet. A higher DII indicates a more pro-inflammatory diet that is not in line with the Dutch dietary guidelines, while a lower DII indicates the opposite: a more anti-inflammatory diet that is in line with the guidelines. We found that the inflammatory potential of the diet was associated with clinical disease activity in Crohn’s disease patients, meaning that patients who consumed a diet more in line with the Dutch dietary guidelines had a lower disease activity and vice versa. No significant association was found in ulcerative colitis patients.

We also used an online survey to investigate associations between level of physical activity of IBD patients and disease activity. We found that the level of physical activity, based on the number of minutes per week and the intensity of activities, was inversely associated with clinical disease activity in Crohn’s disease patients, while no significant association was found in ulcerative colitis patients. Interviews performed to further elucidate the association between physical activity and clinical disease activity revealed that IBD patients generally experience beneficial effects of physical activity, such as improved general fitness, quality of life, and self-image. However, barriers caused by active disease like pain, fatigue and urgency may put them off to be physically active.

Hereafter, an observational study during the Nijmegen Four Days Marches was performed. In that study, we assessed whether moderate-intensity physical activity is safe for IBD patients since this type of physical activity is an important part of the Dutch physical activity guidelines. We found that cytokine responses during this repeated prolonged moderate-intensity walking exercise were not different in IBD patients compared to controls without IBD. Furthermore, faecal calprotectin was not affected by the walking exercise when comparing concentrations of IBD patients who participated in the marches to concentrations of IBD patients who did not. In contrast to these objective findings, there was a slight increase in subjective clinical disease activity in CD patients who participated in the marches, but not in UC patients. Since faecal calprotectin better correlates with endoscopic disease activity than clinical disease activity questionnaires, we overall concluded that it seems safe for IBD patients to perform repeated prolonged moderate-intensity exercise without substantial exacerbation of inflammation.

We then performed a combined lifestyle intervention study based on the Dutch dietary and physical activity guidelines. During this 6-month study, personal dietary and physical activity advice was provided by a dietician and physiotherapist. This resulted in a substantial improvement of diet quality, while the level of physical activity remained the same. Over time, impact of disease on daily life reduced and fatigue decreased, while clinical disease activity, health-related quality of life and faecal calprotectin did not change. Improvement in diet quality was associated with a lower impact of disease on daily life and less fatigue. No associations were found between physical activity and disease-related outcomes.

Lastly, we investigated the use of a web-based tool, the Eetscore, to assess diet quality and provide personalized dietary advice to IBD patients based on the Dutch dietary guidelines. In this prospective cohort study, diet quality of IBD patients improved following dietary advice of the Eetscore and this improvement was associated with a slight improvement in health-related quality of life. The Eetscore seems to be a practical and useful tool to monitor and support a healthy diet in IBD patients.

From this thesis, we conclude that the inflammatory potential of the diet and level of physical activity are associated with disease activity in CD patients, while no associations were found in UC patients. Besides, moderate intensity physical activity does not appear to have harmful effects on IBD and can be safely performed. The Dutch dietary guidelines are consistent with a more anti-inflammatory potential of the diet. When applying the Dutch dietary and physical activity guidelines, impact of disease on daily life and fatigue decreased; likely as a result of a substantial improvement in diet quality. Also, when informing patients about the Dutch dietary guidelines via web-based dietary assessment and advice, diet quality improved.