Western diet and gut inflammation
10th Aug, 2021

Western diet and gut inflammation


A recent study highlights the association between a higher intake of animal and processed foods, alcohol and sugar, with higher levels of intestinal inflammatory markers (1).

The study investigated the relationship between 173 dietary factors and the microbiome of 1,425 individuals in 4 different cohorts: irritable bowel syndrome (IBS) (223 individuals), Crohn's disease (205), ulcerative colitis (126), and healthy controls (871). The mean age of participants was 40-47 years. Dietary intake was assessed through food-frequency questionnaires, and shotgun metagenomic sequencing  was used to profile gut microbial composition and function. Overall, 38 associations were identified between dietary patterns and microbial clusters. A meta-analysis across cohorts found 61 individual foods and nutrients that were associated with 61 microbial species and 249 metabolic pathways.

Processed and animal-derived foods were consistently associated with more Firmicutes, Ruminococcus species of the Blautia genus and endotoxin-synthesis pathways while plant foods and fish were positively associated with short-chain fatty acid (SCFA)-producing commensals and pathways of nutrient metabolism (1). These associations were seen across the board in healthy participants as well as those with IBS or inflammatory bowel disease (IBD).

Knowledge of the pro-inflammatory and anti-inflammatory capacities of single compounds is increasing through functional experiments. The gut microbiome directly affects the balance of pro-inflammatory and anti-inflammatory responses. Microbial competition for nutrients plays a key role in controlling this balance (2).

Another recent study (in mice and humans) showed that a diet high in sugar and fat causes damage to Paneth cells, immune cells in the gut that help keep inflammation in check. When Paneth cells aren't functioning properly, the gut immune system is excessively prone to inflammation, putting people at risk of IBD and undermining effective control of disease-causing microbes (3).

Diets that are high in red meat, animal fat, dairy products, salt, sugar and alcohol, and low in consumption of legumes, vegetables, fruits and seafood, are rich in refined and unhealthy products and are poor in micronutrients such as vitamin A or D, and fibre. This leads to critical changes in both gut microbiota and immune system, negatively affecting the gut integrity, thereby promoting local and systemic chronic inflammation (4,5,6). In contrast, some functional components found in healthy diets, such as probiotics, prebiotics and polyphenols, are beneficial for the restoration of gut health (7).

A previous study showed that participants who consumed a greater amount of animal protein presented a higher Firmicutes/Bacteroidetes ratio, whereas those who consumed less animal protein, had a higher concentration of Bacteroidetes. Participants that consumed more polysaccharides and plant proteins showed higher concentrations of SCFA (8).

The deleterious effects of the consumption of added sugars, particularly from sugar-sweetened drinks, have been reported in the gut microbiota, promoting an increased Firmicutes/Bacteroidetes ratio and reducing the proportion of favourable butyrate-producers such as Lachnobacterium (9). Likewise, added sugars promote increased gut permeability and endotoxaemia , leading to inflammation and systemic complications (10).

The gut microbiota directly influence the intestinal immune system but also affect systemic immune components and are implicated in a growing number of immune-mediated inflammatory diseases, ranging from diabetes to arthritis and systemic lupus erythematosus (11). Gut dysbiosis and associated inflammation have also been implicated in cancer and cardiometabolic disorders (12,13).


Figure 1. Effect on the gut microbiome of a typical western diet (processed foods, sugar, red meat) compared to the Mediterranean diet (14) CC BY 4.0

Figure 1



This study provides additional support for the idea that diet can be a rational strategy for the prevention and management of chronic inflammatory disorders of modern society. Western diet and food industrialisation 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 (15,16,17,18).

While this study highlights the association between processed foods and intestinal inflammation, it’s important to note that other factors such as genetics, ethnicity and environmental influences might also impact inflammation. These factors were not taken into account in the present study. Nonetheless, the results provide additional insight into the importance of a diet that is minimally processed.

Long-term dietary interventions may be most suited for the modulation of the gut microbiota. Although extreme short-term dietary changes may still change the gut microbiota (19,20), there is a tendency for microbial resilience in adults that correlates with long-term habitual diet (21,22,23).

Modulation of gut microbiota through diets enriched in vegetables, legumes, grains, nuts and fish and a higher intake of plant over animal foods, has the potential to prevent intestinal inflammatory processes at the core of many chronic diseases.


1Bolte LA, Vich Vila A, Imhann F, Collij V, Gacesa R, Peters V, et al. Long-term dietary patterns are associated with pro-inflammatory and anti-inflammatory features of the gut microbiome. Gut. 2021 Jul;70(7):1287–98.
2Desai MS, Seekatz AM, Koropatkin NM, Kamada N, Hickey CA, Wolter M, et al. A dietary fiber-deprived gut microbiota degrades the colonic mucus barrier and enhances pathogen susceptibility. Cell. 2016 Nov 17;167(5):1339-1353.e21.
3Liu TC, Kern JT, Jain U, Sonnek NM, Xiong S, Simpson KF, et al. Western diet induces Paneth cell defects through microbiome alterations and farnesoid X receptor and type I interferon activation. Cell Host & Microbe. 2021 Jun 9;29(6):988-1001.
4Christ A, Lauterbach M, Latz E. Western Diet and the Immune System: An Inflammatory Connection. Immunity. 2019 Nov 19;51(5):794–811.
5Statovci D, Aguilera M, MacSharry J, Melgar S. The Impact of Western Diet and Nutrients on the Microbiota and Immune Response at Mucosal Interfaces. Front Immunol. 2017;8:838.
6Bifulco M. Mediterranean diet: the missing link between gut microbiota and inflammatory diseases. Eur J Clin Nutr. 2015 Sep;69(9):1078.
7Wan MLY, Ling KH, El-Nezami H, Wang MF. Influence of functional food components on gut health. Crit Rev Food Sci Nutr. 2019;59(12):1927–36.
8Garcia-Mantrana I, Selma-Royo M, Alcantara C, Collado MC. Shifts on Gut Microbiota Associated to Mediterranean Diet Adherence and Specific Dietary Intakes on General Adult Population. Front Microbiol. 2018;9:890.
9Ramne S, Brunkwall L, Ericson U, Gray N, Kuhnle GGC, Nilsson PM, et al. Gut microbiota composition in relation to intake of added sugar, sugar-sweetened beverages and artificially sweetened beverages in the Malmö Offspring Study. Eur J Nutr. 2021 Jun;60(4):2087–97.
10Jensen T, Abdelmalek MF, Sullivan S, Nadeau KJ, Green M, Roncal C, et al. Fructose and sugar: A major mediator of non-alcoholic fatty liver disease. J Hepatol. 2018 May;68(5):1063–75.
11Forbes JD, Chen C, Knox NC, Marrie R-A, El-Gabalawy H, de Kievit T, et al. A comparative study of the gut microbiota in immune-mediated inflammatory diseases—does a common dysbiosis exist? Microbiome. 2018 Dec 13;6:221.
12Zitvogel L, Pietrocola F, Kroemer G. Nutrition, inflammation and cancer. Nat Immunol. 2017 Jul 19;18(8):843–50.
13Erridge C. Diet, commensals and the intestine as sources of pathogen-associated molecular patterns in atherosclerosis, type 2 diabetes and non-alcoholic fatty liver disease. Atherosclerosis. 2011 May;216(1):1–6.
14García-Montero C, Fraile-Martínez O, Gómez-Lahoz AM, Pekarek L, Castellanos AJ, Noguerales-Fraguas F, et al. Nutritional Components in Western Diet Versus Mediterranean Diet at the Gut Microbiota–Immune System Interplay. Implications for Health and Disease. Nutrients. 2021 Feb 22;13(2).
15Suez J, Korem T, Zeevi D, Zilberman-Schapira G, Thaiss CA, Maza O, et al. Artificial sweeteners induce glucose intolerance by altering the gut microbiota. Nature. 2014 Oct 9;514(7521):181–6.
16Chassaing B, Koren O, Goodrich J, Poole A, Srinivasan S, Ley RE, et al. Dietary emulsifiers impact the mouse gut microbiota promoting colitis and metabolic syndrome. Nature. 2015 Mar 5;519(7541):92–6.
17Chassaing B, Koren O, Goodrich JK, Poole AC, Srinivasan S, Ley RE, et al. Corrigendum: Dietary emulsifiers impact the mouse gut microbiota promoting colitis and metabolic syndrome. Nature. 2016 Aug 11;536(7615):238.
18Yang H, Wang W, Romano KA, Gu M, Sanidad KZ, Kim D, et al. A common antimicrobial additive increases colonic inflammation and colitis-associated colon tumorigenesis in mice. Sci Transl Med. 2018 May 30;10(443):eaan4116.
19David LA, Maurice CF, Carmody RN, Gootenberg DB, Button JE, Wolfe BE, et al. Diet rapidly and reproducibly alters the human gut microbiome. Nature. 2014 Jan 23;505(7484):559–63.
20Klimenko NS, Tyakht AV, Popenko AS, Vasiliev AS, Altukhov IA, Ischenko DS, et al. Microbiome Responses to an Uncontrolled Short-Term Diet Intervention in the Frame of the Citizen Science Project. Nutrients. 2018 May 8;10(5):E576.
21Faith JJ, Guruge JL, Charbonneau M, Subramanian S, Seedorf H, Goodman AL, et al. The long-term stability of the human gut microbiota. Science. 2013 Jul 5;341(6141):1237439.
22Wu GD, Chen J, Hoffmann C, Bittinger K, Chen Y-Y, Keilbaugh SA, et al. Linking long-term dietary patterns with gut microbial enterotypes. Science. 2011 Oct 7;334(6052):105–8.
23Wu GD, Compher C, Chen EZ, Smith SA, Shah RD, Bittinger K, et al. Comparative metabolomics in vegans and omnivores reveal constraints on diet-dependent gut microbiota metabolite production. Gut. 2016 Jan;65(1):63–72.