There is growing evidence to suggest that dietary patterns influence the structure and function of the microbiome in people with inflammatory bowel disease (IBD), the details of which are highlighted in a viewpoint published in The Lancet Gastroenterology & Hepatology.
Changes in the epidemiology of IBD and the increased prevalence in newly industrializing countries have led experts to investigate the role of environmental factors that influence disease etiology and progression. Low habitual fiber intake and other long-term dietary trends are prospectively associated with new-onset IBD. While many human trials that assess outcomes in IBD use dietary interventions, the efficacy of results vary.
As the gut microbiome plays a major role in determining the health of its human host and indicates a level of interindividual variation in its configuration due to diet and intervention, the differences in microbiomes provide researchers with opportunities to study them for personalized precision nutrition.
“Research into microbiome-based predictors of response and research linking microbiome readouts to potential dietary modifications could offer enhanced clinical interventions,” the viewpoint authors wrote.
The researchers described the evolution of dietary patterns and the outcomes they have on the composition and function of the gut microbiome, as well as the role of dietary patterns on immune function and inflammation in people with IBD. In addition, they reviewed new studies analyzing dietary interventions and the implications this research has on the design of future studies that use precision nutrition in IBD.
Patterns in Western diets, which include the increased consumption of red meat and processed meats, prepackaged foods, high fat dairy, and artificial sweeteners, have changed fat consumption patterns, compared with nonwesternized societies. Changes in fiber intake can quickly affect microbial abundance. The increase in saturated fats, decreased monosaturated fats, and an imbalance in the ratio of polyunsaturated fatty acids can all influence gut dysbiosis, thereby causing changes to the intestinal barrier. For example, the increased intake of omega-6 polyunsaturated fatty acids along with the decreased intake of omega-3 polyunsaturated fatty acids are linked to increased permeability of the gut barrier and to endotoxemia.
In addition to fatty acid intake, protein consumption is also associated with alterations to gut microbiota, leading to an increase in microbes that are associated with disease pathogenesis-associated genes and metabolites, including: mucin-degrading bacteria, immunoglobulin G-bound bacteria, proteobacterium phylum, Escherichia coli, Ruminococcus family, and Ruminococcus gnavus. Patients with IBD may also have a decrease in Faecalibacterium prausnitzii.
In patients with IBD, potential mechanistic markers of host-microbe interactions include increased pathogen-associated molecules, an increase in bile acids, and a decrease in short-chain fatty acids. These can, in turn, lead to changes in the intestinal environment such as inflammation, disruptions in mucus layers, reduced thickness, and increased penetrability.
Conversely, the Mediterranean diet is defined by the high intake of vegetables, legumes, nuts, minimally-processed whole grains, extra-virgin olive oil, polyunsaturated and monounsaturated fats, and a lower intake of dairy, eggs, meat, and saturated fats. It also includes greater total and soluble fiber consumption than the Western diet. Adherence to the Mediterranean diet is associated with increased microbial abundance and diversity and a significant reduction in the risk of later-onset Crohn disease.
The Japanese diet includes high daily intake of polyphenol-rich green tea, rice, miso, fruits, vegetables, as well as many weekly servings of fish, soybean, pickles, and seaweed. Although lifestyle changes such as smoking, alcohol intake, and reduced physical activity are confounding factors associated with the microbiota, the rate of IBD in Japan has increased by 9.5 times in the last 3 decades, which is thought to be due to the shift away from the traditional Japanese diet.
As there is still significant variability across populations and timepoints in healthy and disease states, the current understanding of the human microbiome is still limited. Factors associated with the pathogenesis of IBD include genetic susceptibility, microbiome, immune response, and environmental triggers. These factors can often trigger one another.
Current guidelines from the International Organization for the Study of Inflammatory Bowel Disease (IOIBD) recommend that patients with Crohn disease and ulcerative colitis include modest quantities of all macronutrients and increase their nutrient-dense food intake by including more high-fiber fruits and vegetables. The IOIBD also recommends that people with Crohn disease restrict their intake of saturated fats, and that emulsifiers, thickeners, processed foods, trans-fats, and unpasteurized dairy be restricted for all patients with IBD. In addition, the guidelines recommend the restriction of red meat and myristic acid intake for people with ulcerative colitis.
Microbiome modifications using evidence-based dietary interventions are often challenging. Exclusive enteral nutrition is the only current, well-established dietary intervention for microbiome modification, especially for luminal Crohn disease in children; however, long-term maintenance of remission is not often achieved, although this may be due to low compliance. Because other dietary interventions do not take biological mechanisms and interindividual heterogeneity into consideration, they provide only modest success.
Merging a patient’s genetic and environmental background with their metabolic, genomic, and microbial profiles may allow for better dietary treatment approaches for disease prevention and management.
“With developments in nutrigenomics and integration of individual-level data on genetic and metabolic profiles and environmental exposures, personalised nutrition advice and improved clinical outcomes should be feasible. Such individual-level stratification of the intestinal ecosystem will lead to more specific modulation of inflammation by diet, and can perhaps be combined with microbe, microbial products, or pharmaceutical agents for more effective interventions,” concluded the authors.
Disclosure: Multiple authors declared affiliations with industry. Please refer to the original article for a full list of disclosures.
Sasson AN, Ingram RJM, Zhang Z, et al. The role of precision nutrition in the modulation of microbial composition and function in people with inflammatory bowel disease. Lancet Gastroenterol Hepatol. Published online July 13, 2021. doi:10.1016/S2468-1253(21)00097-2