NEW YORK (Reuters Health) - A higher intake of animal and processed foods, alcohol and sugar is associated with higher levels of intestinal inflammatory markers, researchers say.
"It was surprising, to see such a clear association between what we consider a healthy diet and a healthy gut microbiota composition, and on the other hand less healthy dietary patterns associated with pathobionts and inflammatory markers," said Laura Bolte of the University of Groningen and Dr. Rinse Weersma of University Medical Centre Grongingen, in the Netherlands.
"This was not only observed in patients with inflammatory bowel disease (IBS), but also in healthy controls, implying a role for dietary strategies already at the public-health level," they told Reuters Health in a joint email.
As reported in Gut, the two researchers and their colleagues investigated the relationship between 173 dietary factors and the microbiome of 1,425 individuals spanning four cohorts: IBS (223 individuals) Crohn's disease (CD, 205), ulcerative colitis (UC, 126), and controls (871).
Across cohorts, the mean age ranged from 41 to 47; men made up about half of the UC and control groups, about a third of the CD group and less than a fifth of the IBS group.
Dietary intake was assessed through food-frequency questionnaires, and shotgun metagenomic sequencing was used to profile gut microbial composition and function.
Among the findings with regard to diet, individuals with IBS consumed less bread, potatoes, cheese, spreads and yogurt drinks than controls, which was reflected by a lower protein and plant protein intake. Specifically, protein intake was 68.1 g/day for IBS versus 74.8 g/day for controls and for plant protein, 27.3 g/day versus 30.8 g/day.
Protein and vegetable intake was also lower in CD compared with controls, at 67.1 g/day versus 74.8 g/day and 98.1 g/day versus 109.4 g/day, respectively.
Overall, the researchers identified 38 associations between dietary patterns and microbial clusters. In a meta-analysis across cohorts, 61 individual foods and nutrients were associated with 61 species and 249 metabolic pathways.
For example, processed foods and animal-derived foods were consistently associated with more Firmicutes, Ruminococcus species of the Blautia genus and endotoxin-synthesis pathways. The opposite was true for plant foods and fish, which were positively associated with short-chain fatty acid-producing commensals and pathways of nutrient metabolism.
Bolte and Dr. Weersma said, "Our study provides additional support for the idea that diet can be a rational strategy for the management of chronic inflammatory disorders of modern society. Western diet and food industrialization parallel the rising incidence of IBD in previously considered low-risk countries, and functional studies already show that additives included during food processing, such as artificial sweeteners, are associated with pro-inflammatory changes in the gut microbiome."
"All this evidence adds to the importance of diet for disease development," they said. "Therefore, it is important that we promote healthier dietary habits as clinicians and continue the investigation of consequences of diet and lifestyle."
Dr. Fatima Cody Stanford of the Massachusetts General Hospital Weight Center, in Boston, who was not involved in the study, told Reuters Health by email, "We have known that processed foods negatively impact the gut microbiota while less processed (foods) have a positive impact on the gut microbiota. Also, it is not surprising that plant-based foods have the most beneficial profile."
"We must remember that these are associations," she noted. "These provide additional insight on the importance of a diet that is minimally processed, but associations are just that. Genetics, race/ethnicity, and environmental influences may all have an impact on inflammation. It is highly unlikely that the authors accounted for any of these factors. Indeed, this is not noted in the manuscript."
