T cells are critical mediators of adaptive immunity. When T cells recognize pathogens through T-cell receptors, together with costimulatory signals provided by antigen-presenting cells, T cells expand clonally and traffic to tissues, thereby triggering an adaptive immune response. However, an excessive immune response usually leads to severe tissue damage. In contrast, T_reg cells can limit the immune response from T_eff cells to avoid overwhelming inflammatory responses, a process known as “immune tolerance” (66). Several recent studies have shown SCFAs to be critical factors in balancing adaptive immunity and immune tolerance (28, 67). SCFAs produced by inulin fermentation maintain immune homeostasis by suppressing excessive innate responses and stimulating specific adaptive immunity.

The metabolic and functional changes of cluster of differentiation (CD)8⁺ T cells are partially mediated by inulin and SCFAs. Inulin treatment promotes the infiltration CD8⁺ T cells in tumors of several mouse models, and induces a shift to a pro-inflammatory tumor microenvironment (68–70). Furthermore, SCFAs (e.g., butyrate) can regulate the metabolism of CD8⁺ T cells by acting on FFAR3, thereby ensuring rapid and sustained activation of T_eff cells during viral infections (28). In contrast, the mechanisms by which inulin and SCFAs limit autoimmune responses by regulating T_reg cells differentiation are more complex. Butyrate promotes production of extra-thymic T_reg cells in an intronic enhancer CNS1-dependent manner if administered systemically, but increases only intracolonic T_reg cells production if administered locally via an enema (71). Conversely, acetate and propionate promote the accumulation of intracolonic T_reg cells in an FFAR2-dependent manner (66).

IL-10 is a key cytokine for T_reg cells to exert anti-inflammatory effects. IL-10 is secreted by T_reg subsets that express the transcription factor forkhead box P3 (Foxp3). Thus, T_reg cells expressing Foxp3 are crucial in limiting intestinal inflammatory responses (34). An independent study showed that supplementation with long-chain inulin-type fructans promoted the proliferation of CD25⁺ Foxp3⁺ CD4⁺ T_reg cells and reduced the number of IL17A⁺ CD4⁺ T-helper (Th)17 cells, thereby modulating T cell responses and suppressing intestinal inflammatory responses (55). In addition, metabolites of inulin (e.g., propionate) regulate the proliferation and differentiation of CD25⁺ Foxp3⁺ T_reg cells (66, 72). Propionate also improves angiotensin II-induced inflammatory responses by modulating T_reg cells (73).

Histone acetyltransferase (HAT) and histone deacetylase (HDAC) are important for regulating gene expression. Usually, a high acetylation level indicates active transcriptional activity. A low acetylation level is associated with transcriptional repression. In the intestine, if HDAC is overexpressed, the balance of gene expression is disrupted and cell proliferation is abnormal, which eventually leads to tumorigenesis (74). In contrast, the gut microbiota can inhibit HDAC activity by fermenting inulin into SCFAs, thereby regulating the acetylation level of histones and affecting epigenetic changes in immune cells (75, 76). An independent study showed that inulin dietary treatment inhibited HDACs activity (including HDAC2 and HDAC8), and induced protective epigenetic changes in mouse mammary tumor cells (77). In another animal experiment, consumption of an inulin diet increased the level of SCFAs (especially butyrate), which enhanced the host antimicrobial program by inhibiting HDAC3 (23). Similarly, Fernández et al. found that administration of inulin-rich products reduced the number of colon polyps in two animal models of colorectal cancer (CRC), which may be related to HDACs regulation (78). Furthermore, a study using isotope tracing revealed inulin-derived SCFAs to provide carbon sources for histone acetylation (76).Notably, SCFAs are also involved in regulating epigenetic changes and energy metabolism of B cells by suppressing the activity of HDACs (79–82).

In particular, SCFAs contribute significantly in the fight against intestinal inflammation by promoting T_reg cells differentiation through the inhibition of HDACs. Butyrate has also been found to be a potent inhibitor of HDACs (83). Furusawa and colleagues found that butyrate produced by obligate anaerobic bacteria improved colitis by promoting histone H3 acetylation in the promoter and conserved non-coding sequence regions of the Foxp3 locus, thereby supporting differentiation of T_reg cells and enhancing intestinal immune tolerance (84). In addition to directly promoting the differentiation of CD4⁺ T-cell precursors into T_reg cells, butyrate and propionate can induce the differentiation of extrathymic T_reg cells and reduce expression of pro-inflammatory cytokines within DCs by inhibiting HDACs activity (71). Propionate enhances histone acetylation in colonic T_reg cells, drives the proliferation and differentiation of T_reg cells, and enhances T_reg cell-mediated inhibition of colitis. These effects of propionate appear to be dependent on activation of FFAR2 (66). Nevertheless, whether the inhibitory effect of SCFAs on HDACs is dependent on expression of FFAR2 and FFAR3 is controversial, because SCFAs seem to enter cells directly through membrane transport proteins on the cell surface (85). Furthermore, although butyrate and propionate can inhibit HDACs and promote the proliferation and differentiation of T_reg cells, acetate appears to lack this inhibitory activity towards HDACs (71).

Immune cells and cytokines are crucial in the development and regression of inflammatory responses. Inflammation is characterized by excessive infiltration of immune cells (e.g. macrophages, neutrophils), which subsequently release pro-inflammatory cytokines. Simultaneously, regression of inflammatory responses requires the release of anti-inflammatory factors (e.g. IL-10) by immune cells. Inulin and its metabolites can selectively support the development of Th1 and Th17 effector cells and IL-10⁺ T_reg cells, depending on the cytokine milieu and immunological context. SCFAs promote the differentiation of IL-10⁺ CD4⁺ T cells under a physiological state. Once the immune response is initiated, SCFAs turns to support the proliferation of T_eff cells, such as Th1 and Th17 cells (85). Therefore, inulin and its metabolites modulate the balance of the immune response, setting a reasonable “immune tension” that allows T cells to clear harmful substances but avoids exaggerating the level of tissue damage.

ILCs are an important subpopulation of natural immune cells. ILCs (like B cells and T cells) develop from common lymphoid progenitor cells, and share some common characteristics with T cells. However, ILCs do not express antigen-specific receptors (e.g., T-cell receptors, B-cell receptors). In addition, ILCs do not undergo thymic selection, clonal selection, or clonal expansion. Therefore, ILCs respond rapidly to tissue infection and pathogens, but the effector molecules produced are the same as those in Th cells. ILCs can be classified into four categories according to the cytokines they secrete: ILC1s secrete interferon (IFN)-γ; ILC2s secrete IL-5, IL-9, and IL-13; ILC3s secrete IL-22, IL-17A/F, and granulocyte macrophage-colony stimulating factor; regulatory ILC cells secrete IL-10 (86, 87). Multiple GPCR receptors are expressed on the surface of ILCs, and SCFAs have been found to activate GPCR receptors on ILCs and promote tissue repair and host defense, which contributes to regulating adaptive immunity (88–91).

Allergens lead to type-2 inflammatory responses, which are mediated by Th2 cells, ILC2s, and their secreted cytokines. Type-2 inflammatory responses can stimulate B cell proliferation to produce antibodies, mediate humoral immunity, participate in barrier immunity at mucosal surfaces, and play a part in counteracting parasitic infections and allergic diseases (92). An inulin fiber diet promotes type-2 immune responses after spirochete infection in an eosinophil-dependent manner (93). Furthermore, an increased activity of ILC2s plays a key part in asthma development (94), and inulin intervention has been reported to reduce the number of airway eosinophils and improve asthma by suppressing HDAC9 expression in people suffering from asthma (95). Furthermore, direct supplementation with SCFAs can also suppressed ILC2s and lung-related allergic reactions (96).

However, in contradiction to previous evidence, Arifuzzaman and colleagues showed that inulin increased systemic levels of bile acids (particularly cholic acid), which led to an increased IL-33 level via activation of the farnesoid X receptor (FXR) pathway. IL-33 secretion caused subsequent activation of ILC2s and the production of IL-5, leading to increased eosinophilia which exacerbated airway allergic responses (93). SCFAs-mediated FFAR2 expression has been shown to trigger phosphoinositide 3-kinase (PI3K), signal transducer and activator of transcription (Stat)3, Stat5, and mammalian target of rapamycin pathways to promote ILC2s proliferation. However, SCFAs also seem to inhibit the proliferation of ILC2s through a non-FFAR2-mediated mechanism (88). Thus, inulin may maintain optimal amounts of ILC2s in peripheral tissues to modulate type-2 immune responses during infections through multiple pathways. The immunological outcomes of consuming an inulin fiber diet are dependent upon the interactions between various microbiota-derived metabolites and different immunomodulatory pathways (93).

As a member of the IL-10 family, IL-22 has an important role in intestinal immune regulation. IL-22 has been reported to promote epithelial cell proliferation and induce the production of Reg3γ and other antimicrobial peptides (97). ILC3s, γδT lymphocytes and CD4⁺ T cells are the main cell types that secrete IL-22 in the gut (98). Inulin has been reported to promote colon epithelial remodeling by increasing γδT lymphocyte-induced IL-22 production (99). In addition, HFD consumption disrupts enterocyte proliferation, leading to an impaired intestinal barrier, low-grade inflammation, and metabolic syndrome. Conversely, inulin supplementation in a HFD impacts microbiota and promotes IL-22 expression in an ILC3s-dependent manner, which fortifies the intestine, thereby resulting in reduced microbiota encroachment and expression of pro-inflammatory genes (100). Several studies have also shown that SCFAs, which are products of the fermentation of DF (including inulin), promote the proliferation of ILC3s and CD4⁺ T cells and subsequent production of IL-22 through several mechanisms (101, 102).

Toll-like receptors (TLRs) recognize different pathogen-associated molecular patterns and trigger the production of pro-inflammatory factors in macrophages (103). However, sustained production of pro-inflammatory cytokines and chemokines can lead to disruption of immune homeostasis. As a TLR4 ligand, inulin activates TLR4 and regulates expression of inflammatory factors in monocytes (104). Butyrate has been shown to reverse the abnormal expression of ZO-1 and reduce LPS translocation as well as inhibit macrophage activation, pro-inflammatory cytokine production, and neutrophil infiltration, thereby reducing liver injury in rats (105). Similarly, Qiao et al. found that butyrate inhibits the production of TNF-α and IL-6 and myeloperoxidase activity by blocking NF-κB activation in Kupffer cells (106). In ulcerative colitis (UC), butyrate also inhibits NF-κB activation in macrophages and reduces mucosal inflammation (107). In a Staphylococcus aureus-induced mastitis model, intake of high-dose inulin was shown to inhibit HDAC3 by promoting butyrate production in mice, thereby activating the macrophage-mediated antimicrobial defense program (23). Moreover, butyrate administration in influenza-infected mice remodeled bone-marrow hematopoiesis, promoted production of Ly6c^- monocytes, and enhanced alternative macrophage activation, thereby inhibiting CXCL1 production, neutrophil recruitment, and the immune response during infection (28). Recently, the protective effect of butyrate was also observed in a peripheral blood mononuclear cell (PBMC) model of gout, in which butyrate downregulated the production of the pro-inflammatory cytokines IL-1β, IL-6, and IL-8 by inhibiting HDACs (108). In conclusion, these evidences suggest a protective role of inulin and SCFAs in regulating monocyte-macrophage-mediated protection in inflammatory responses and immune processes.

Metabolic syndrome is largely caused by physical inactivity and excess caloric intake. Patients with metabolic syndrome often have abdominal obesity, insulin resistance, hyperglycemia, hyperlipidemia and hypertension. Growing evidence suggests that obesity and metabolic disorders are associated with ecological dysbiosis of the gut microbiota, and that increased intake of DF is beneficial in improving ecological dysbiosis (131, 132). Thus, dietary inulin is a potential agent for improving disorders of glucose and lipid metabolism (20, 125, 128).

Studies have demonstrated that inulin intake modulates ecological dysbiosis, reduces the level of fasting glucose, attenuates insulin resistance, and improves lipid disorders (126, 127). However, some patients may suffer from mild gastrointestinal discomfort, including bloating and loose stools (45, 120, 121, 123). In a mouse model of a Western diet (42% of calories from fat, 43% of calories from carbohydrates, and 15% of calories from protein)-induced dysbiosis colonized with human vegan microbiota, inulin supplementation rendered a shift from protein hydrolysis to glycolytic fermentation of the gut microbiota. This action resulted in fewer sulfur-containing compounds and more SCFAs, which contributed to improved lipid denaturation and glucose homeostasis (133). The same improvement in the metabolism of glucose and lipids was also observed in ob/ob mice upon inulin treatment (42). Inulin also shows a significant improvement in type I diabetes mellitus (T1DM) in addition to T2DM. Disruption of the gut barrier leads to activation of pancreatic islet-reactive T cells and triggers autoimmune T1DM (134, 135), and diet is one of the most important factors in affecting gut homeostasis. Several studies have shown that an inulin-rich diet can promote a beneficial gut microbiota composition, and increase expression of TJ proteins and mucins, thereby preventing and/or treating T1DM (55, 136, 137). The improvement of T1DM by inulin is dependent on its modulation of the intestinal metabolic profile because the fermentation of inulin by gut microbiota promotes SCFAs production and a subsequent increase in the number of Foxp3⁺ T_reg and IL-10⁺ Tr1 cells, which may limit activation of pancreatic islet- reactive T cells (138).

Intriguingly, another study found that mice supplemented with inulin undertook more locomotive activity than those supplemented with cellulose. Those data suggested that inulin intake intensified the willingness of mice to exercise and promoted energy expenditure in obese mice (139). However, the mechanisms behind these changes are largely unknown and may be related to the regulation of the nervous system by inulin metabolites. Guo et al. found that inulin could modulate neurological disorders through the microbiome-gut-brain axis (140). In addition, Shulman and colleagues reported that a HFD induced an increase in acetate production in the intestine of mice, and then the increased acetate level led to activation of the parasympathetic nervous system and promoted secretion of growth hormone-releasing peptide and glucose-stimulated insulin. In that study, direct stimulation of isolated pancreatic islets with acetate failed to promote insulin secretion. However, these changes were not observed when the parasympathetic nerves were cut off, which indicated that parasympathetic nerves in the gut-brain-pancreatic-β-cell axis might be involved in the regulation of inulin or its metabolites (141). However, other researchers have reported no significant effect on appetite after inulin intake

IBD includes Crohn’s disease and UC. Chronic intestinal inflammation is the typical feature of IBD. IBD development is associated with environmental factors, genetic conditions, faults in the immune system, and changes in the microbiota (142). Inulin has been reported to limit intestinal inflammation, modulate the intestinal microbiome, and improve intestinal barrier function. A randomized controlled trial supported the notion that oligofructose-enriched inulin can improve gastrointestinal symptoms in patients with active UC without significant side effects (143). Therefore, inulin is also being used increasingly for IBD treatment (144, 145).

The ameliorative effect of inulin on IBD is related mainly to its: reshaping of intestinal microbiota structure; promoting the growth of beneficial bacteria; inhibiting expression of inflammatory factors; improving the intestinal mucosal barrier. As mentioned above, inulin significantly increased the abundance of beneficial bacteria such as Bifidobacterium rhamnosus. In an animal model induced by DSS, inulin combined with Lactobacillus rhamnosus increased the abundance and diversity of intestinal microbiota, decreased expression of pro-inflammatory cytokines, and relieved UC (146). In a study comparing the differences between inulin and another type of DF, the authors found that inulin had a modulatory effect on the microbiota of mice with DSS-induced colitis, reduced expression of pro-inflammatory cytokines significantly, and improved intestinal barrier function (147). Those results support that the notion that DFs (especially inulin) are promising dietary supplements to alleviate intestinal inflammation. In addition, inulin can be used as an immune- system modulator for the treatment and management of IBD, and its mechanism is related to the promotion of secretion of antimicrobial peptides and improvement of intestinal mucosal immunity (148).

Results in animal IBD models and humans suggest that inulin intake can help to improve the intestinal mucosal barrier and suppress intestinal inflammation (149), but some research teams have reached opposite conclusions. For example, Armstrong and colleagues found that unfermented inulin induced secretion of pro-inflammatory cytokines in a subset of IBD intestinal biopsies cultured ex vivo (150). In several other animal studies, researchers have found that dietary supplementation with inulin may be beneficial for low-grade inflammation and associated metabolic disease, but that it also exacerbates the severity of DSS-induced acute colitis (151–153). Furthermore, treatment with an “antibiotic cocktail” led to intestinal ecological dysregulation and induced colitis in mice, whereas supplementation with inulin-type fructans delayed the recovery of this antibiotic-induced intestinal inflammation and decreased the recovery of T_reg and B cells in the lamina propria. Moreover, although supplementation with inulin-type fructans inhibited expression of certain pro-inflammatory genes in the colon (e.g., inducible nitric oxide synthase, TNF-α), it also reduced sIgA secretion in the colon. Inulin also increased the serum level of LPS, reduced secretion of the anti-inflammatory mediator transforming growth factor-β1, and promoted secretion of the pro-inflammatory cytokine IL-17A (154). In a study on the anti-tumor effect of inulin, inulin promoted the infiltration of γδ T cells and production of IFN-γ in tumors, but also led to expression of several inflammation-related genes in IECs, including TNF-α, cyclooxygenase-9, and MMP-9, thereby exacerbating inflammation in the intestine, but this seems to be associated with immune surveillance. Inulin also triggered the expression of macrophage inflammatory protein-2, IL-22 and the transcription factor Foxp3 in CD45⁺ cells in the lamina propria, and these were beneficial in suppressing inflammation. Those results suggest that an inulin diet triggers activation of γδ T cells in epithelial lymphocytes and immune surveillance in IECs, as well as induction of tissue repair signals and tolerance in cells of the lamina propria (69).

Overall, inulin is beneficial for IBD because it reshapes the intestinal microbiota structure, suppresses intestinal inflammation, and improves intestinal cellular and mucosal immunity. However, the gas produced by fermentation of inulin may aggravate the gastrointestinal symptoms of patients, thus limiting its beneficial effects (155). In two randomized controlled clinical trials, inulin ingestion did not change appetite, intestinal permeability, or levels of inflammatory biomarkers, but caused flatulence and soft stools (122, 124).

Urea accumulation associated with CKD can affect the composition of the gut microbiome and increase the permeability of the intestinal epithelial barrier. If the intestinal barrier is breached, uremic substances, including indole sulfate, para-cresol sulfate, and trimethylamine N-oxide (TMAO), can lead to endotoxemia and systemic inflammation (156, 157). Recently, modification of the gut flora by supplementation with prebiotics has been considered to be a potential therapeutic strategy to reduce uremic toxins of intestinal origin and inflammation. For example, inulin supplementation changed the composition of intestinal microbiota, reduced serum levels of uric acid, and increased degradation of fecal uric acid in patients with renal failure (129). Moreover, intake of inulin-type fructans limited the production of indoles (precursors of indoxyl sulfate) in patients undergoing peritoneal dialysis (158). Similar results were observed by Mitrović et al. They found that inulin treatment reduced the serum level of indoxyl sulfate, improved the glomerular filtration rate, and reduced the level of high sensitivity C-reactive protein levels by altering the gut microbiota composition in patients with CKD (159). In addition, long-term consumption of inulin-containing fructan water reduced serum levels of glucose, total cholesterol, uric acid and creatine kinase in mouse offspring, suggesting that inulin-type fructans contribute to a reduced risk of kidney disease (160).

However, in another study, intervention with inulin-type fructans (10 g/day) for 3 months altered composition of gut microbiome, but did not reduce the plasma TMAO level in patients undergoing peritoneal dialysis (130). This observation may be related to the duration and dose of the intervention. Furthermore, according to the results of a prospective cohort study, higher dietary inulin intake also failed to reduce the incidence of CKD and cardiovascular disease in the population, but prevented hypertension and T2DM, which are major risk factors for cardiovascular and renal events (161). Therefore, given that inulin showed an overall benefit or a neutral effect, inulin is considered to be a safe and reliable strategy to improve the uremic toxin and micro-inflammatory state in patients with CKD (159).

ILC2s and Th2 cells are among the key effector cells in allergic diseases, and the cytokines they secrete (IL-4, IL-5, IL-13) mediate the allergic immune response (162). Inulin and its intestinal metabolites (SCFAs) may be involved in mediating the amelioration of allergic diseases by regulating ILC2s and Th2 cells.

Several studies have shown that inulin supplementation in mice during gestation or lactation induced the growth of beneficial bacteria in the intestine of maternal mice. These beneficial bacteria could also be transferred to their offspring, enhance their intestinal barrier function, and increase the number of B-cell and T_reg subpopulations in lymph nodes. These actions shaped a more tolerogenic immune environment that suppressed Th2 responses to alleviate food allergy (163, 164). Furthermore, in airway allergic responses, propionate ameliorates inflammation by altering bone-marrow hematopoiesis in mice via FFAR3, promotes the production of DC precursors, and inhibits the differentiation capacity of Th2 cells (72). Several studies have demonstrated that inulin diets exhibit benefits for allergic diseases (including asthma), but inulin itself can cause rare allergic reactions (e.g., itching, rash, swelling, wheezing, difficulty in breathing, unconsciousness) (165–167).

In addition, inulin (especially delta inulin) has been used as an adjuvant to enhance the immune response (168). Venom immunotherapy is effective in improving anaphylactic reactions to stings from Hymenoptera spp, but it can also cause severe (and even life-threatening) immune reactions. Plant-based polysaccharide delta inulin is a new adjuvant with low reactogenicity that can enhance vaccine immunogenicity and antigen-sparing. A randomized controlled trial reported the benefit of delta inulin as an immune adjuvant in patients with bee-venom allergy, and found that delta inulin increased the levels of specific IgG₄ significantly during the early induction phase (169). In conclusion, even though inulin may cause allergic reactions, the function of inulin as a dietary supplement to alleviate allergic diseases (e.g., food allergies, asthma) or as an adjuvant to enhance vaccine efficacy has been demonstrated widely and utilized.

Dietary supplementation with whole grains and DF usually reduces the incidence of tumors as well as the risk of postoperative oncologic complications and tumor-related mortality (170, 171). Studies have observed the tumor growth inhibitory effects of inulin, though the mechanisms remain largely unexplored (172, 173). Nevertheless, several mechanisms pertaining to the activity and regulation of inulin in anti-tumor immunity have been elucidated in recent years.

Perhaps the anti-tumor effects of inulin rely largely on its ability to promote immune cell recruitment to the tumor microenvironment. Two studies found increased infiltration of immune cells in the tumor bed after supplementation with an inulin-rich diet (69, 70). Upon subcutaneous injection of a syngeneic B16- ovalbumin melanoma tumor, inulin uptake promoted infiltration of CD4⁺ and CD8⁺ T cells and increased IFN-γ production, thereby triggering an effective Th1 anti-tumor response and inhibiting tumor growth. Meanwhile, inulin treatment increased expression of chemokines (CCL4, CCL8), inflammatory vesicle-related genes (TLR3, TLR7) and antigen presentation-related genes (CD40, Stat1, ICOS), induced anti-tumor immunity, and inhibited the growth of colon tumors. Moreover, either alone or in combination with SCFAs, inulin affected tumor growth, indicating that the anti-tumor effects of inulin were not dependent on SCFAs (70). Notably, in addition to B16-OVA melanoma tumors, the anti-tumor effects of inulin were also confirmed in tumor models of MCA205 fibrosarcoma and MC38 colorectal cancer (CRC) cell lines, and such effects were associated with the response of Th1 cells (69). In addition, γδ T cells are unconventional T cells that recognize metabolism-related molecules and have potent anti-tumor activity. Inulin can activate γδ T cells via γδ T cell receptor signaling, and promote IFN-γ production (174). In mice with 1,2-dimethylhydrazine-induced colon cancer, the amelioration of colon cancer in mice by inulin involved modulation of Janus kinase-1/β-catenin signaling (175).

In liver-associated tumors, the anti-tumor effect of inulin is associated with its metabolites and subsequent immunomodulation. In mice with hepatocellular carcinoma (HCC), an increased acetate level by fecal-bacterial transplantation or direct administration of acetate inhibited the activity of HDACs, increased acetylation of sex-determining region Y-box transcription factor 13 (Sox13) at site K30, and decreased expression of Sox13, thereby reducing IL-17A production by ILC3s and retarding tumor growth. In addition, a combination of acetate with blockade of programmed death (PD)-1/PD-1 ligand promoted anti-tumor immunity significantly and enhanced the treatment efficacy of PD-1 (176).

Inulin has shown protective and tumor-suppressive effects in most CRC studies, but other reports have indicated that inulin intake promotes CRC development. The reason for this discrepancy may be due to differences in gut microbial composition. Inulin supplementation led to increased colonization of polyketide synthase-positive (pks⁺ ) E. coli strain NC101, whereas pks⁺ Escherichia coli can promote carcinogenesis and facilitate CRC progression through the production of colistin (a genotoxin that induces double-stranded DNA breaks) (177). Therefore, given the prevalence of pks⁺ E. coli in healthy and CRC populations, individuals colonized with pks⁺ bacteria should use inulin with caution (178). Furthermore, supplementation of inulin can induce cholestasis and HCC, which may be due to inulin fermentation (179).