## 4 Discussion  
Onion (_Allium cepa_) is well known for its activities against free radicals and oxidative damage associated with chronic diseases. The phytochemicals in onion include glucosinolates, flavonoids, isoflav, phenolic acids, phytoestrogens, and carotenoids [26], which provide health benefits such as antioxidant and anti-inflammatory activities. However, onions are considered a high-FODMAP food (10-16% fructans) [27]. FODMAPs include di- and monosaccharides such as fructose and lactose, oligosaccharides originating from fructans and galactans, and polyols [28]. The fructans in onion are poorly absorbed in the human small intestine due to the lack of digestive enzymes. Like many other dietary fibers, they are not digested in the upper gastrointestinal tract and pass through to the large intestine, where they are fermented and utilized by the colonic microbiota, yielding gas [29]. FODMAPs show a negative effect on IBD patients by triggering the symptoms of IBD such as bloating, pain, discomfort, diarrhea, and flatulence. Several studies confirmed that the reduction in FODMAPs in the diet reduces symptoms of irritable bowel syndrome (IBS) [25; 28; 30; 31; 32]. Recent studies have reported that fermentation increases the bioavailability of bioactive compounds including phenolic compounds, flavonoids, and SCFAs, and the consumption of fermented foods increased microbiome diversity and decreased inflammation markers in humans [10; 11; 33]. Fermentation may improve FODMAP properties and gut health. Fermentation increases the production of cell wall-degrading enzymes such as cellulolytic, ligninolytic, and pectinolytic enzymes that may reduce FODMAP and may increase glycosases, which are responsible for hydrolyzing the glycosidic bond of phenolic compounds, resulting in the production of an aglycone form (a molecule without a glycoside chain), which improves absorbability in the intestine [34]. It has been reported that the fermentation of onion raised the content of quercetin (also known as an aglycone) [9], which is one of the most common bioactive compounds found in onions. In order to determine whether fermented onion also improves DSS-induced IBD in human gut health, we orally administered 10-20 g of fresh onion/kg rat/day to each rat, which is equivalent to about one bulb (100-200 g) of fresh onion/60 kg of person/day. Figure 7: GC analysis of short-chain fatty acid (SCFA) content in the digestive cesium of rats. AA, acetic acid; PA, propionic acid; BA, butyric acid. Control, saline; DSS, dextran sulfate sodium; PC, positive control, probiotic; LO, low dose of fermented onion; HO, high dose of fermented onion; FO, fresh onion. Values are expressed as mean \(\pm\) SEM (\(n=8\)); different symbols in the bar graph were representative of statistical significance at (\(p<0.05\)) measured by one-way ANOVA followed by Tukey’s test for multiple comparisons. *\(p<0.05\) vs. CON, **\(p<0.05\) vs. DSS, *\(p<0.05\) vs. PC, **\(p<0.05\) vs. LO, ***\(p<\) vs. HO. The crypts in the intestine provide stem cells with a safe environment for the renewal of the intestinal epithelium, which occurs every 3 to 4 days [35]. The high dose of fermented onion group (HO, 20 g/kg rat) showed significantly lower crypt damage compared to DSS and FO groups, in which crypts showed loss of parallelism, and irregularity in size, spacing, and shape (Figure 2). Crypt damage can lead to a reduction in the number of goblet cells that are produced by the stem cells at the bottom of the crypt. In contrast to the HO group, which showed a significantly high number of goblet cells, there is a loss of goblet cells in the DSS and FO groups. The goblet cells help to maintain the integrity of the intestinal epithelium by secreting mucin, which contributes to the ongoing replenishing of the mucus layer [18]. Therefore, the integrity of goblet cells causes increased mucus production, which is followed by an increase in the thickness of the inner mucus layer, as demonstrated in the HO group (Figure 3).