Inflammatory diseases significantly enhance morbidity and mortality among patients. One of the most common chronic inflammatory diseases is Inflammatory Bowel Disease (IBD), which significantly affects the daily life of patients. IBD can affect the gut epithelial barrier function and promote alterations in the gut microbiome. Recently, scientists reviewed the role of sulforaphane from cruciferous vegetables (e.g., broccoli) in preventing IBD by regulating inflammation and altering the gut microbiome. This review is available in The Journal of Nutritional Biochemistry.
Review Article: Interplay of Broccoli/Broccoli Sprout Bioactives with Gut Microbiota in Reducing Inflammation in Inflammatory Bowel Diseases. Image Credit: Pakhomov Andrey / Shutterstock
IBD Symptoms and Occurrences
IBD is associated with host-microbe-environment interactions in the human gastrointestinal (GI) tract. Common symptoms of IBD include diarrhea, abdominal pain, weight loss, fatigue, and bloody stool. In addition, IBD patients are at risk of having concurrent cardiovascular disease, arthritis, cancer, and kidney or liver disease.
There are two primary forms of IBD, i.e., ulcerative colitis (UC) and Crohn’s Disease (CD). As the name suggests, UC occurs in the colon, and inflammation is found along the mucosal epithelial layer. CD is an autoimmune disorder, and, in this case, inflammation might occur anywhere in the GT tract. Several studies have indicated that prolonged inflammation could result in colorectal cancer (CRC). In addition, some IBD patients experience overlapping clinical symptoms of UC and CD.
Although a global prevalence of IBD has been recorded, the most significant incidence was observed in the United States, the United Kingdom, Canada, and western European counties. IBD development is maximum in populations with high-stress levels and reduced access to essential resources (e.g., education, employment, and good living conditions).
IBD is caused due to various factors that include environmental, genetic, and immune responses. In IBD and CRC patients, a higher concentration of pro-inflammatory interleukin (IL) cell signaling peptides, such as IL-6 and IL-8, were found in the plasma and serum samples.
Typically, palliative treatment is used to reduce IBD symptoms. This approach targets inflammation to improve host homeostasis and gut microbiome composition. Even though over-the-counter drugs for inflammation cause ulcers, non-steroidal anti-inflammatory treatments (NSAIDs) and corticosteroids reduce the risk of cancer incidence. NSAIDs are also associated with side effects and disruption of the gut microbiome. Hence, there is an urgent need for novel non-steroidal treatment to cure chronic inflammation while maintaining GI function and microbial communities.
Microbial therapeutics, such as probiotics and fecal microbial transplant (FMT), have shown promising results in IBD treatment. In addition, plant-derived bioactive metabolites with non-steroidal anti-inflammatory properties play an important role in restoring host-microbial homeostasis and gut health. For instance, dietary bioactives, such as sulforaphane, can mitigate the inflammatory response.
Effectiveness of Broccoli Sprout Bioactive Metabolites in Remediating IBD
A diet rich in cruciferous vegetables, such as broccoli and broccoli sprouts, was found to reduce inflammation, which has been linked to a reduced risk of cancer. Importantly, bioactive metabolites related to broccoli and broccoli sprouts were found to improve both forms of IBS, i.e., UC and CD.
A high intake of cruciferous vegetables has been correlated with decreased serum levels of pro-inflammatory cytokines, such as IL-1β, TNFα, and IL-6. It also promoted the inhibition of NFκB.
Cruciferous vegetables contain glucosinolates (GSLs), which can be metabolized into various compounds. Isothiocyanates (ITCs) are a byproduct of GSLs categorized as dietary bioactive metabolites with anti-inflammatory and anti-cancer activities. Epithiospecifier protein (ESP) is a metabolite in the plant cell cytoplasm and converts GSL to ITC-nitrile. Since these compounds denature at high temperatures, cooked broccoli exhibits lower ITC and GSL concentrations.
Sulforaphane (SFN), a type of ITC, is found in mature broccoli and broccoli sprouts. Several studies have indicated that SFN regulates inflammation pathways by inhibiting NF-ᴋB. This downregulation of pro-inflammatory cytokines is extremely important for developing and maintaining IBD. Theoretically, SFN inhibits NF-ᴋB by interacting with Keap1, suppressing polyubiquitination and promoting Nrf2 nuclear accumulation.
Recent documents provided strong evidence of the interaction between broccoli and broccoli sprouts and gut microbiota. This interaction provided stronger protective effects against GI inflammatory diseases. Several studies have shown that SFN is metabolized by GI bacteria. Importantly, this compound also prevents microbiome dysbiosis and improves barrier function. These functions help in reducing the severity of IBD-like colitis in mouse models. Therefore, as the gut microbiome aids in the production of broccoli sprout-derived bioactives, changes in the gut microbiota can affect its availability and efficacy in preventing IBS.
Alteration of Gut Microbiota by SFN
Although it is known that broccoli can modify gut microbiome, the exact roles of fiber and ITCs for this modification are not yet known. Nevertheless, mice fed with a broccoli stem diet and human cells treated with SFN revealed improved lipid metabolism markers, balanced gut microbiome, and reduced triacylglycerols. SFN-enriched broccoli diet reduced Desulfovibrionaceae and Mucispirillum schaedleri, which are associated with pro-inflammatory activity in the GI tract.
Broccoli diets enhance the concentration of Bacteroides in human gut microbiota. In addition, enhancement in Clostridium spp., Proteobacteria, and butyrate-producing bacteria was observed. Interestingly, an individual’s BMI was found to influence the modification of microbiota by broccoli diets. An in vivo experiment revealed that mice fed with 10% freeze-dried broccoli for around two weeks improved cecal microbiota to hydrolyze GLR.
Based on the evidence, broccoli and sprouts effectively improve gut microbiota and reduce inflammation in irritable bowel syndrome.