The relationship between gluten and gut microbiota is currently the subject of growing scientific interest, especially in order to understand how a gluten-free diet may influence the balance of intestinal bacteria.<\/b><\/i><\/p>\n
Abstract<\/span><\/strong> Highlights<\/span><\/strong> The paradox of the gluten-free diet<\/span><\/strong><\/p>\n A gluten-free diet represents the indispensable treatment for celiac disease and is increasingly widespread also among non-celiac individuals. However, in recent years several studies have observed that adopting a gluten-free diet may be associated with changes in the composition of the gut microbiota.<\/p>\n In particular, some studies have reported:<\/p>\n reduction in Bifidobacterium<\/p>\n<\/li>\n reduction in Lactobacillus<\/p>\n<\/li>\n increase in Enterobacteriaceae<\/p>\n<\/li>\n<\/ol>\n These alterations have been observed not only in patients with celiac disease but also in healthy individuals who adopt a gluten-free diet.<\/p>\n The explanation most frequently proposed attributes such changes to the reduction of fermentable carbohydrates present in gluten-containing cereals, such as fructans and arabinoxylans. The gut microbiota can in fact use fermentable fibers coming from many other dietary sources, including legumes, fruit, vegetables, seeds and resistant starch. Moreover, gluten is a protein that during digestion generates numerous peptides partially resistant to enzymatic degradation, some of which may reach the intestine and be further metabolized by the microbiota. is it possible that the human microbiota, especially in populations with high consumption of gluten-containing cereals, has also developed a metabolic adaptation toward peptides derived from incomplete gluten digestion?<\/p>\n At present there are no definitive answers, but this hypothesis represents an interesting field of research for better understanding the relationship between gluten, diet and gut microbiota.<\/p>\n 1. Gluten-free diet and changes in the microbiota<\/span><\/strong> 2. The most common interpretation: reduction of fermentable carbohydrates<\/strong> 3. A critical point: fibers can come from many other sources<\/strong> 4. What happens to gluten during digestion<\/span><\/strong> 5. The role of the microbiota in gluten degradation<\/span><\/strong> 6. Bioactive peptides derived from gluten<\/span><\/span><\/strong> 7. The central role of short-chain fatty acids<\/span><\/strong> In-depth section<\/span><\/strong> Adaptation of the microbiota to the diet<\/span><\/strong> Modifying the ecological balance of some bacterial populations:<\/strong> In summary<\/span><\/strong> Conclusion<\/span><\/strong> The gut microbiota is a complex ecosystem whose stability depends above all on the availability of fermentable fibers and plant polysaccharides. At the same time, gluten is a protein partially resistant to digestion and its degradation can generate numerous peptide fragments that reach the intestine and can be further metabolized by the microbiota.<\/p>\n In addition to the possible ecological role of these peptides as substrates for some bacterial populations, gluten digestion can also generate bioactive peptides with potential biological effects, including modulation of inflammation, protection of the intestinal mucosa and antimicrobial activity. The physiological role of many of these peptide fragments in humans, however, remains still poorly clarified.<\/p>\n The gut microbiota is a complex ecosystem that depends above all on the availability of fermentable fibers and plant polysaccharides. At the same time, the possible role of peptides derived from incomplete gluten digestion represents a field of research that is still little explored. Better understanding these interactions will be fundamental to clarify the relationship between gluten, diet and gut microbiota health and to evaluate whether peptides derived from gluten may play a functional role in the intestinal ecosystem.<\/p>\n Scientific bibliography<\/span><\/strong> [2] Golfetto L. et al. [3] Bonder MJ. et al. [4] Kaliciak I. et al. [5] Hansen LBS. et al. [6] Sanz Y. [7] Prandi B. et al. [8] Gianfrani C. et al. [9] Sanchiz A. et al. [10] Mamone G. et al. [11] Pecora F. et al. Glossary<\/strong> 2. Enzymatic substrate<\/strong> 3. Metabolite<\/strong> \n","protected":false},"excerpt":{"rendered":" The relationship between gluten and gut microbiota is currently the subject of growing scientific interest, especially in order to understand how a gluten-free diet may influence the balance of intestinal bacteria. Abstract A gluten-free diet is the main treatment for celiac disease and is increasingly widespread also among non-celiac individuals. Several studies have shown that […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[73],"tags":[3579,3573,3575,3561,3565,3591,3583,3593,3559,3563,3557,3571,3567,3577,3585,3569,3581,3589,3587],"class_list":["post-13277","post","type-post","status-publish","format-standard","hentry","category-article","tag-bifidobacterium-gluten-microbiota","tag-celiac-disease-microbiota","tag-dysbiosis-celiac-disease-microbiota","tag-gluten-and-gut-microbiota","tag-gluten-digestion-microbiota","tag-gluten-digestion-peptides-microbiota","tag-gluten-fermentation-gut-bacteria","tag-gluten-free-diet-gut-bacteria-changes","tag-gluten-free-diet-gut-microbiota","tag-gluten-free-diet-microbiome","tag-gluten-gut-microbiota","tag-gluten-microbiome-research","tag-gluten-peptides-microbiota","tag-gut-bacteria-gluten-digestion","tag-gut-microbiota-fiber-fermentation","tag-gut-microbiota-gluten","tag-lactobacillus-gluten-microbiota","tag-scfa-gut-microbiota","tag-short-chain-fatty-acids-microbiota"],"yoast_head":"\n
\nA gluten-free diet is the main treatment for celiac disease and is increasingly widespread also among non-celiac individuals. Several studies have shown that adopting a gluten-free diet may be associated with changes in the composition of the gut microbiota, including a reduction in Bifidobacterium and Lactobacillus and an increase in Enterobacteriaceae. The most common interpretation attributes such changes to the reduction of fermentable carbohydrates present in gluten-containing cereals. However, fermentable substrates for the microbiota may also derive from many other dietary sources. Gluten is also a protein partially resistant to digestion, and its degradation may generate peptides that reach the intestine and are further metabolized by the microbiota. This article analyzes the available evidence on the relationship between a gluten-free diet and gut microbiota and discusses the still little explored hypothesis of a possible ecological role of peptides derived from incomplete gluten digestion in the intestinal microbial ecosystem.<\/p>\n
\n1 – A gluten-free diet may modify the gut microbiota.
\n2 – In some studies a reduction in Bifidobacterium and Lactobacillus is observed.
\n3 – The most common explanation is the reduction of fermentable fibers present in wheat.
\n4 – However, the microbiota can also obtain fibers from legumes, fruit, vegetables and resistant starch.
\n5 – Gluten is a protein partially resistant to digestion and some of its peptides reach the intestine.
\n6 – The microbiota possesses enzymes capable of degrading these peptides.
\n7 -The possible ecological role of gluten peptides in the microbiota is a field of research that is still little explored.<\/p>\n\n
\nHowever, this interpretation raises some questions.<\/p>\n
\nThis raises a question that is still little explored:<\/p>\n
\nSeveral studies show that adopting a gluten-free diet may be associated with changes in the gut microbiota.
\nIn particular, the following have been observed:
\n1 – decrease in Bifidobacterium
\n2 – decrease in Lactobacillus
\n3 – increase in Enterobacteriaceae
\nThese changes have been detected both in subjects with celiac disease even after years of a gluten-free diet, and in healthy individuals adopting a gluten-free diet [1][2][3].
\nA study conducted on healthy subjects showed that a short-term gluten-free diet is associated with:
\n1 – reduction in Bifidobacterium
\n2 – reduction in Lactobacillus
\n3 – increase in Escherichia coli and Enterobacteriaceae [1].
\nAlterations of the microbiota have also been observed in celiac patients treated with a gluten-free diet, suggesting that normalization of the microbiota does not always occur completely despite clinical remission of the disease [2][4].
\nSome studies report that 60\u201380% of celiac patients still show intestinal dysbiosis despite a correct gluten-free diet. Probiotics and dietary modifications can modulate the microbiota in celiac patients, but no therapy has yet demonstrated that it can stably correct dysbiosis<\/b><\/span><\/p>\n
\nThe explanation most frequently proposed is that a gluten-free diet entails a reduction of fermentable complex carbohydrates, with a consequent decrease in the substrates available for beneficial intestinal bacteria. By eliminating cereals such as wheat, rye and barley, the intake of some components of the wheat food matrix is in fact reduced, including:
\n1 – fructans
\n2 – arabinoxylans
\n3 – some fermentable fibers
\nThese compounds are important substrates for the gut microbiota and contribute to the production of beneficial metabolites such as short-chain fatty acids [5][6].
\nAccording to this interpretation, therefore, the alterations observed in the microbiota would be mainly due to the modification of the food matrix and the intake of fermentable fibers, rather than to the absence of gluten itself [5].<\/p>\n
\nHowever, fermentable substrates for the microbiota can come from many other dietary sources, including:
\n1 – legumes
\n2 – fruit
\n3 – vegetables
\n4 – seeds
\n5 – tubers
\n6 – rice
\n7 -resistant starch
\nNumerous studies indicate that the following are particularly important for microbiota health:
\n1 – fermentable fibers
\n2 – complex plant polysaccharides
\n3 – resistant starch<\/b>
\ncomponents that do not depend exclusively on wheat consumption.
\nTherefore, claiming that the wheat food matrix is indispensable for maintaining intestinal eubiosis is not supported by definitive evidence.<\/p>\n
\nGluten is a complex protein composed mainly of:
\n1 – gliadins
\n2 – glutenins<\/b>
\nDuring gastrointestinal digestion some protein sequences are particularly resistant to enzymatic hydrolysis. This happens because gluten contains sequences rich in proline and glutamine, which make complete degradation by human digestive enzymes difficult [7][8].
\nConsequently, some peptides derived from gluten digestion may reach the small intestine and the colon in the form of partially digested protein fragments.<\/p>\n
\nSeveral intestinal bacteria possess enzymes capable of further degrading peptides derived from gluten.
\nAmong the most studied genera are:
\n1 – Lactobacillus
\n2 – Bifidobacterium
\n3 – Bacteroides
\n4 – some species of Clostridium
\nThese microorganisms possess microbial peptidases capable of degrading proline-rich sequences present in gluten peptides [9][10].
\nSome studies also suggest that specific strains of Bifidobacterium and Lactobacillus may reduce the formation of toxic gliadin peptides and modulate the immune response associated with gluten [11].<\/p>\n
\nA further little explored aspect concerns the possibility that microbial degradation of gluten produces peptides with biological activity. Proteomic analyses have shown that gluten digestion generates numerous peptide fragments with potential biological and immunological activity [7][12].
\nEnzymatic digestion of food proteins can in fact generate bioactive peptide fragments with different biological functions, including:
\n1 – modulation of inflammation
\n2 – protection of the intestinal mucosa<\/b><\/span>
\n3 – antimicrobial activity.
\nAmong these, the following have been described, for example:
\n1 – the peptide \u03c9-gliadin \u03c9(105-123) from einkorn, which in in vitro studies showed protective effects on the intestinal mucosa
\n2 – the peptide p10mer (QQPQDAVQPF) identified in some wheat varieties
\nThese results suggest that gluten degradation could generate biologically active peptides. The physiological role of many of these peptides in humans remains still poorly clarified and represents an emerging field of research.<\/p>\n
\nThe gut microbiota performs numerous important metabolic functions, including the production of short-chain fatty acids (SCFAs):
\n1 – butyrate
\n2 – propionate
\n3 – acetate
\nThese metabolites derive mainly from the fermentation of dietary fibers and perform fundamental functions:
\n1 – nourishment of intestinal epithelial cells
\n2 – strengthening of the mucosal barrier
\n3 – modulation of the immune system
\n4 – reduction of intestinal inflammatory processes.
\nFor this reason, the intake of fermentable fibers is considered one of the most important dietary factors for maintaining the balance of the microbiota [6].<\/p>\n
\n<\/span>Can undigested gluten have an ecological role in the microbiota?<\/span><\/strong><\/p>\n
\nAn aspect rarely discussed in the relationship between gluten and microbiota concerns the possible role of gluten peptides that are not completely digested. Since some gluten sequences resist enzymatic digestion, part of the protein fragments can reach the colon. Some microorganisms of the microbiota possess enzymes capable of further degrading these peptides. Among the most studied genera are:
\n1 – Lactobacillus
\n2 – Bifidobacterium
\n3 – some species of Clostridium
\n4 – Bacteroides
\nHere these peptides can be used as a metabolic substrate by some intestinal bacteria, thanks to the presence of specific microbial peptidases [9].<\/p>\n
\nThe gut microbiota is strongly influenced by the habitual diet of populations.
\nIt has been demonstrated that:
\n1 – populations with a diet rich in plant fibers show microbiotas dominated by Prevotella
\n2 – Western populations show greater prevalence of Bacteroides
\nThis demonstrates that the human microbiota can adapt to the food sources habitually consumed.
\nSince in Western countries the consumption of gluten-containing cereals has been very high for millennia, it is plausible that part of the human microbiota has also adapted to the presence of peptides derived from incomplete gluten digestion. If this hypothesis were correct, the complete elimination of gluten could modify the ecological balance of some bacterial populations. At present, however, this hypothesis has not yet been demonstrated and requires further studies.<\/p>\n
\nThe possible modification of the ecological balance of the gut microbiota could consist above all in changes in the composition and functions of the bacterial communities of the intestine:
\n1. Reduction of some bacteria \u201cadapted\u201d to gluten<\/strong>
\nIf some intestinal microorganisms are capable of using peptides derived from gluten as a substrate, completely eliminating gluten could:
\nreduce the availability of this nutrient
\ndecrease the growth of those bacteria that metabolize it.
\n2. Increase of other bacterial species<\/strong>
\nWhen a nutritional source changes, other bacterial species can become more competitive and increase in number. This can lead to a different proportion among the various bacterial groups.
\n3. Changes in the metabolic products of the microbiota<\/strong>
\nIntestinal bacteria produce substances that are important for the organism, such as:
\nshort-chain fatty acids (SCFAs): acetate, propionate, butyrate
\nvitamins
\nmetabolites that influence the immune system.
\nIf bacterial species change, the quantity or type of metabolites produced may also change.
\n4. Possible effects on digestion and immunity<\/strong>
\nA different microbiota balance could theoretically influence:
\nthe digestion of some nutrients
\nintestinal permeability
\nthe intestinal immune response.<\/p>\n
\nThe modification of the biological balance could mean:
\n1 – change in the bacterial species present
\n2 – change in their proportions
\n3 – change in the metabolic substances produced by the microbiota.
\nHowever, as mentioned in the text, this hypothesis is still under study and there is no definitive evidence that the elimination of gluten significantly modifies the microbiota in healthy people.<\/p>\n
\nScientific evidence indicates that a gluten-free diet may modify the composition of the gut microbiota. However, it is still not clear whether such changes are mainly due to the reduction of fermentable fibers, to overall dietary modifications, to adaptations of the microbiota, or to the absence of gluten itself.<\/p>\n
\n[1] De Palma G. et al.
\nEffects of a gluten-free diet on gut microbiota and immune function in healthy adult human subjects
\nBritish Journal of Nutrition, 2009
\nDOI: 10.1017\/S0007114509993533
\nAbstract \u2013 key points<\/strong>
\nstudy on healthy adults following a gluten-free diet
\nreduction in Bifidobacterium and Lactobacillus
\nincrease in Enterobacteriaceae and E. coli
\nreduction in the intake of fermentable polysaccharides.<\/p>\n
\nLower bifidobacteria counts in adult patients with celiac disease
\nBMC Gastroenterology, 2014
\nDOI: 10.1186\/1471-230X-14-86
\nKey points<\/strong>
\nreduced abundance of Bifidobacterium in celiac patients
\npersistent alterations of the microbiota even with a gluten-free diet.<\/p>\n
\nThe influence of a short-term gluten-free diet on the human gut microbiome
\nGenome Medicine, 2016
\nDOI: 10.1186\/s13073-016-0295-y
\nKey points<\/strong>
\nthe gluten-free diet modifies the composition of the microbiota
\nvariations observed especially in fermenting bacteria.<\/p>\n
\nInfluence of gluten-free diet on gut microbiota composition in patients with coeliac disease: a systematic review
\nNutrients, 2022
\nDOI: 10.3390\/nu14102083
\nKey points<\/strong>
\nsystematic review of studies on microbiota and celiac disease
\nthe microbiota in treated celiac patients often remains altered.<\/p>\n
\nA low-gluten diet induces changes in the intestinal microbiome
\nNature Communications, 2018
\nDOI: 10.1038\/s41467-018-07019-x
\nKey points<\/strong>
\nrandomized study on healthy adults
\na low-gluten diet modifies the microbiota and intestinal fermentation.<\/p>\n
\nEffects of a gluten-free diet on gut microbiota and immune function
\nGut Microbes, 2010
\nKey points<\/strong>
\ndiet is one of the main factors that modulate the microbiota
\ncomplex carbohydrates represent a key energy substrate.<\/p>\n
\nPeptides from gluten digestion: comparison between old and modern wheat varieties
\nFood Chemistry, 2017
\nDOI: 10.1016\/j.foodchem.2016.12.120
\nKey points<\/strong>
\nidentification of numerous peptides derived from gluten digestion.<\/p>\n
\nGliadin peptides resistant to gastrointestinal digestion
\nJournal of Immunology Research
\nKey points<\/strong>
\nsome gluten peptides resist digestion
\nthey interact with the intestinal immune system.<\/p>\n
\nMicrobial peptidases: key players in reducing gluten immunogenicity
\nApplied Sciences, 2025
\nKey points<\/strong>
\nmicrobial enzymes degrade gluten peptides.<\/p>\n
\nAnalytical and functional approaches to assess gluten immunogenicity
\nFrontiers in Nutrition, 2023
\nKey points<\/strong>
\nanalysis of gluten proteins and derived peptides.<\/p>\n
\nGut microbiota in celiac disease
\nFrontiers in Immunology, 2020
\nKey points<\/strong>
\nBifidobacterium and Lactobacillus modulate the response to gluten.<\/p>\n
\n1. Metabolic substrate<\/strong>
\nIt is the molecule that is used in a metabolic reaction to produce energy or to be transformed.
\nExamples:<\/strong>
\nglucose
\nfatty acids
\namino acids
\nPractical example:<\/strong>
\nGlucose is a metabolic substrate of glycolysis, because it is degraded to produce ATP.<\/p>\n
\nIt is the specific molecule on which an enzyme acts.
\nEach enzyme recognizes a specific substrate (like a key in a lock).
\nExample:<\/strong>
\nlactase enzyme
\nsubstrate: lactose
\nThe enzyme transforms the substrate into products.<\/p>\n
\nIt is any molecule that participates in metabolism, so it can be:
\na substrate
\na product
\na reaction intermediate
\nExample in glycolysis:<\/strong>
\nglucose \u2192 glucose-6-phosphate \u2192 fructose-6-phosphate
\nThese intermediate molecules are metabolites.<\/p>\n