Smoking and Diet: Impact on Disease Course?

The impact of current smoking on inflammatory bowel disease (IBD) course has been studied extensively; smoking is deleterious in Crohn's disease (CD), and beneficial in ulcerative colitis (UC). Except for enteral nutrition, there are only limited data regarding the impact of diet on disease course.

Current smoking worsens the course of CD, increasing the incidence of flares, the need for steroids, immunosuppressants and re-operations. Conversely, smoking cessation has a rapid beneficial effect on disease course, decreasing the risk of flares and of post-operative recurrences. From 3 months after the quit date, quitters have a disease course similar to that of never smokers. Achieving smoking cessation in CD is thus an important goal of therapy. On the contrary, smoking improves the course of UC and in particular, is associated with a decreased need for colectomy. Smoking cessation increases the risk of flare and the need for steroids or immunosuppressants. However, patients with UC should not be discouraged to quit, because the beneficial effect of smoking for their disease is counterbalanced by the deleterious systemic effects of tobacco. Among dietary interventions, only exclusive enteral nutrition was shown to induce remission and achieve mucosal healing in some patients with CD. The beneficial effect of liquid-defined diet is observed whatever be the type of administration (orally or by tube), the type of diet regarding protein and fat content and resulting alterations in the gut microbiota. In UC, enteral nutrition has no effect. Finally, popularized restrictive diets in IBD as the specific-carbohydrate diet and the gluten-free diet have not been rigorously tested. In a small trial, a semi-vegetarian diet was shown to be effective in maintaining remission over 2 years in CD.

Patients with IBD should not smoke and avoid passive smoking. Aside from the defined liquid diets, there is no rationale for advising particular diets.