Though the benefits of probiotics have been studied for almost a century, only recently have their use skyrocketed, partly owing to the current COVID-19 pandemic. Even if you are not currently consuming probiotics, chances are the thought might have crossed your mind at least once. After all, the current health food buzzword is probiotics, and so many people seem to be consuming them. Be it the ever-simple yogurt or drinks like Yakult or even probiotic capsules, the benefits advertised are many-fold, and one should incorporate them in some form in their diet, especially if experiencing gut health issues (Fig 1).
However, as you begin a journey on improving your gut health, focusing on both prebiotics and probiotics can have compounded benefits when compared to your probiotic regimen alone. Well, what are prebiotics and what do they do?
Prebiotics are defined as fermented short chain oligosaccharides, or fibres, that enhance the activity of our intestinal micro-flora. Simply put, prebiotics are “good food” for your intestinal bacteria and help them to produce functional metabolites, that improve our bodily health. To be functional, a prebiotic must be resistant to colonic digestion by the host while undergoing fermentation by the intestinal microbiota. Applying this definition, there are several digestive fibers which can be utilised as prebiotics. Generally, these include resistant starch, fructo-oligosaccharides (FOS), galacto-oligosaccharides (GOS), and several non-starch polysaccharides. These undergo fermentation and ultimately get released as short chain fatty acids or SCFAs, which aid in several physiological functions of our body.
Now that we know their benefit, one can obtain their prebiotics naturally, from several foods, including chicory root, artichokes, garlic, onion, and cereals such as wheat, barley and millet (Fig 2). If you already have a diet rich in fiber, you can start adding probiotic foods, and vice versa if you already consume probiotics. Either way, it is imperative to modify your diet to add more fiber to have a healthy gut. You will have small issues like bloating, flatulence, or other disorders when you practice a poor diet – constituting less fibre intake – and if continued long term, it can become chronic and may even lead to inflammatory diseases like inflammatory bowel disease (IBD), colitis, persistent diarrhea and other gastrointestinal conditions.
It has been demonstrated that our gut is connected to our brain through a network of millions of neurons, and bidirectional signals between the brain and our gut through the vagus nerve can alter the GI tract’s sensory and motor function whilst impacting our brain functions too. Our enteric nervous system (ENS) regulates our gut function through peristalsis, absorption, and secretion, while our autonomic nervous system (ANS) does the same using the central nervous system (CNS), by controlling digestion, bile secretion, mucus levels and more. As mentioned earlier, SCFAs produced from the fermentation of prebiotics are absorbed into our blood circulation, and reach various tissues, including our brain where they play a pivotal role in regulating our neurological functions. Several mice model studies have confirmed that the SCFAs play a role in ENS homeostasis, stress alleviation, and promote regularity of our neural systems (Everard et al, 2011; Savignac et al, 2015; Burokas et al, 2017). Additionally, some prebiotics are known to increase our native gut microbiome proliferation, promote anti-inflammation, and reducing anxiety-like behaviors signaling a direct effect on our brain function trough the gut-brain axis. However, it’s not just the nervous system that is the point of action for the prebiotics. As you build up your fiber intake, the accretion of the chewing time in the oral cavity can promote saliva and gastric acid production, which also contributes towards higher satiety (Parnell et al, 2006). This also affects our insulin, and ghrelin (hunger hormones) secretions, eventually regulating our food intake and promoting satiation (van der beek et al, 2018). However, the most interesting claim for prebiotic intake is the supposed health implications on our gut immunity. One may be confused about the term “gut immunity”, and rightly so. Though it is well known that our immune system is composed of several barriers, our gut encounters the majority of antigens, and any immunogenic compromise can have adverse health effects almost immediately. So, it is no surprise that the major player in our immune system is located in our gastrointestinal tract – gut associated lymphoid tissue (GALT). GALT induces immune reaction by activating T cells, dendritic cells, macrophages, and mast cells in response to pathogenic entry and prebiotics can enhance our GALT’s action. SCFAs are known to reduce the occurrence of colon cancer, colitis, and may also inhibit colonization of pathogenic bacteria to our epithelial lining through anti-inflammatory pathways (Komiyama et al, 2011; Rivera-Huerta et al, 2017; Rani et al, 2019). Among other functions, SCFAs also act as signaling factors and increase the production of regulatory T cells, improving our gut immunity (Freitas et al, 2014). SCFAs produced by our gut microbiome also increase calcium bioavailability, thereby increasing our bone density and improving iron absorption. Epidemiological research has also suggested a link between a low prebiotic diet and cardiovascular diseases (Kochar et al, 2007; Tang et al, 2019). SCFAs alter lipid metabolism, and possibly lower your risk for heart diseases, by reducing the LDL cholesterol serum concentrations. Overall, the promising benefits of prebiotics promote them as a powerful tool for altering your microbial composition and to strengthen your immunity.
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