An influence of diet on IBD risk is plausible
One mechanism through which diet may exercise a causal influence on the risk of IBD is by affecting the microbiome. In 2011, investigators studied 98 healthy volunteers who answered questionnaires about their diet. The researchers also used 16s rDNA sequencing to characterize the population’s stool samples. A diet high in animal protein, amino acids, and saturated fats was associated with large populations of Bacteroides. A diet low in fat and in animal protein, but high in carbohydrates and simple sugars was associated with large populations of Prevotella. When the investigators conducted a controlled-feeding study of 10 patients, microbiome composition changed within 1 day of initiating a high-fat-and-low-fiber or a low-fat-and-high-fiber diet (Science. 2011;334[6052]:105-8.). A more recent study showed that the diversity of the microbiome increased with the adoption of an animal-based diet (Nature. 2014;505[7484]:559-63.).
Diet also may exert a causal influence on IBD risk by altering the intestinal barrier. In an experimental model, 5-mg/mL concentrations of fiber from plantain and broccoli significantly reduced the translocation of Escherichia coli through a human intestinal epithelial barrier (Gut. 2010;59[10]:1331-9.). Increased fiber intake may thus result in reduced intestinal inflammation, said Dr. Ananthakrishnan.
Observational and experimental evidence thus support an effect of diet on the risk of IBD, and experimental evidence indicates that this effect is biologically plausible. Nevertheless, “there are many missing links,” and further study will clarify the role of diet in IBD incidence, said Dr. Ananthakrishnan.