Health Promoting Benefits of Edible Mushrooms through Gut Microbiota

The traditional medicinal system has used foods as medicines; one such kind of traditional remedy commonly used consists of mushrooms with medicinal properties. There are several edible mushrooms that have significant medicinal metabolites. These mushrooms can make better prebiotics to stimulate the gut microbiota. 

Prebiotics are substances that induce the growth or action of microorganisms (e.g., bacteria and fungi) that contribute to the well-being of their host . Prebiotics are identified based on the composition of fibers in them. Some of the commonly-known prebiotic foods are as follows: raw chicory root (64.6%), raw Jerusalem artichoke (31.5%), raw dandelion greens (24.3%), raw garlic (17.5%), and raw onion (8.6%). Apart from those mentioned above, mushrooms are also considered a potential source of prebiotics as they contain different polysaccharides, such as chitin, hemicellulose, mannans, α- and β-glucans, galactans, and xylans .

Mushrooms have the advantage of their easy availability and having been studied extensively, when compared to other prebiotics. Mushrooms contain various active polysaccharides and phenolic compounds make it biologically valuable. The gut microbiota comprises of trillions of bacteria that contribute to the nutrient acquisition and energy regulation. The microorganisms present in the gut play an important role in the health of the digestive system, and also have an influence on the immune system. The immune tissues in the gastrointestinal tract constitute the largest and most complex fraction of the human immune system.

Mushrooms were found to play a vital role in immunoregulating pneumococcal pneumonia, atherosclerosis, and antitumor activities. In a recent study, researchers have found that white button mushrooms (WB mushrooms) increase microbial diversity and accelerate the resolution of Citrobacter rodentium infection in mice. Specifically, WB mushrooms were reported to stimulate a local inflammatory response, the production of catecholamines, and their metabolites, and changed the composition of the gut flora. The results of their study provide information on biological changes that occur upon WB ingestion are likely to include direct stimulation of the innate immune systems that produce inflammation and affect the composition of the gut flora which improves GI health by limiting the damage that occurs following injury or infection. Another interesting study provides evidence for hypocholesterolemia properties and prebiotic effects of Mexican Ganoderma lucidum in C57BL/6 mice. In brief, the study explains significant reduction in lipogenic gene expression (Hmgcr, Fasn, Srebp1c, and Acaca) and genes responsible for reverse cholesterol transport (Abcg5 and Abcg8), as well as an increase in Ldlr gene expression in the liver and delineate a new source of bioactive compounds with hypocholesterolemic and prebiotic effects.

Ganoderma lucidium (GL) is a frequently mentioned mushroom that has been reported to reduce obesity in mice by modulating the composition of gut microbiota. GL reduces body weight, inflammation, and insulin resistance in mice fed a high-fat diet. The GL not only reverses gut dysbiosis—as indicated by the reduced Firmicutes/Bacteroidetes ratios and endotoxin-bearing Proteobacteria levels—but also alters the intestinal barrier probity and attenuates endotoxemia. The results confirm that GL can be used as a prebiotic agent to prevent gut dysbiosis and obesity-related metabolic disorders in obese individuals. Mushrooms are shown to improve the antioxidant status via microbiome alterations. The consumption of Agaricus bisporus mushroom affects the intestinal microbiota composition, performance, and morphology, and antioxidant levels of turkey poults. The results of this study state that A. bisporus is able to improve both growth performance and antioxidant activity of turkey poults and it also significantly increased the numbers of lactic acid-producing bacteria and improved the condition of the intestine.

Gut microbiota composition has been reported to alter the gut barrier, affect adipose tissue proliferation, and affect energy metabolism, all of which can be changed through the use of prebiotics. Lentinula edodes-derived polysaccharide alters the spatial structure of gut microbiota in mice; in brief L2 treatment decreased the gut microbiota’s diversity and evenness in the intestine, particularly in the colon and cecum. Other populations also changed in response to L2 treatment include Proteobacteria, Acidifaciens, Bacteroides,  Helicobacter suncus, and Alistipes. Recently some researchers have evaluated the prebiotic properties of edible mushrooms, the selected mushrooms; Pleurotus ostreatus, P. sajor-caju, and P. abalonus represent the bifidogenic effect which can stimulate the growths of Bifidobacterium bifidum TISTR 2129, B. breve TISTR 2130, B. animalis TISTR 2195, and B. longum TISTR 2194 . This study acknowledges that these mushrooms should be studied in future for their assistance in improving hosts health via its prebiotic properties. It is evident that in the above studies that mushroom can act as potential prebiotics to improve the microbiome in favor of host health. There are about 380 or more species of mushrooms that are proven to possess medicinal properties, so a large number of prebiotic sources may be encountered in the future.

Mushroom polysaccharides have been suggested to be potential prebiotics. Lentinula edodes-derived polysaccharide rejuvenates mice in terms of immune responses and gut microbiota. L2 reverses the gut microbiota structure, such as the reduced ratio Firmicutes/Bacteroidetes, the increased Bacteroidia, the decreased Bacilli and Betaproteobacteria, the increased Bacteroidaceae, the decreased Lactobacillaceae, and Alcaligenaceae. Phellinus linteus has been proved to have anti-tumor properties on skin, lung, and prostate cancer cells. Phellinus linteus induces changes in the composition and activity of the gastrointestinal tract microbiota that confer nutritional and health benefits to the host. The Trametes versicolor is a polypore mushroom. Polysaccharopeptide from Trametes versicolor regulates the gut microbiota to maintain the host health. Hericium erinaceus is a Chinese mushroom with nootropic properties that is also known as Lion’s Mane. H. erinaceus renders changes in the composition and activity of the gastrointestinal tract microbiota that confer nutritional and health benefits to the host.

Microbiota play a significant role in human health and disease; often they are referred to as the “forgotten organ”. So far the research on the regulation of microbiota by various mushrooms has been insufficiently studied.

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