Shiitake

Shiitake (Lentinula edodes) is not only a proven medicinal mushroom. Due to its aromatic smell and taste, the fungus is also sought after as a delicacy and enjoys great popularity especially in Asian cuisine. The aroma is mainly created by eight carbon atoms (C8 aromas) alcohols and ketones which have a characteristic mushroom smell. In addition to the C8 molecules, sulfurous compounds also contribute to an intense garlic-like aroma. The substances responsible for this include lenthionine, dimethyl disulfide, dimethyl trisulfide and 1,2,4-trithiolane. The umami taste of shiitake, which intensifies the inherent taste of food, is mainly due to non-volatile compounds such as 5-ribonucleotides and the amino acids aspartate and glutamate.¹ 

Lentinian, the bioactive beta-glucan fraction of shiitake, is considered an efficient immune system stimulator. It improves the release of IgA on the mucosal surfaces, increases the formation of monocyte-specific T cells and intensifies the cytotoxic effect of macrophages on bacteria and viruses.⁴ The oral intake of Lentinula edodes also leads to an increased formation of special antibodies (IgG2 and IgM heterophilic antibodies),⁵ which can build up additional specific immune protection. Shiitake shows well documented antibacterial and antifungal effects. In an animal study, the number of intestinal bacteria decreased significantly after feeding Lentinula edodes, which was attributed to the antibacterial ingredients such as lenthionin, terpenoids and polyphenols.⁶
 

In addition to a general boost of the body's own immunological activities, shiitake extract also appears to increase the intestine-associated immune defence. In animal experiments, the number of lymphocytes in the small intestine increased by 40 % after oral administration of shiitake.⁷ In healthy subjects, more B-cells circulated after 6 weeks of taking Lentinula edodes.⁸ Changes in the composition of the intestinal flora have also been documented.^9,10 Thus, Lentinula edodes can increase the growth of probiotic bifidobacteria and lactobacteria, which in turn activates the intestine-associated immune defence and thus promotes the immune functions of the entire organism.¹⁰
 

For some time now, Lentinula edodes has been the focus of scientific interest because of its lipid-modulating and weight-reducing properties.¹¹ These effects can be attributed to different mechanisms, including the modulation of the intestinal microbiome.¹² Lentinula-edodes fungal fibres serve as a substrate for the digestion and metabolism of intestinal microbes. The metabolites excreted by the intestinal microbes alter the host's energy balance, absorption in the intestine, appetite and lipid metabolism and thus have effects on weight and fat metabolism.⁹ In 2014, an in vivo study suggested that shiitake changes the body's fat metabolism. For example, in animals fed a high-calorie, high-fat diet, triacylglycerol did not accumulate in the fatty tissue but in the liver.¹¹ The cholesterol regulating effect of shiitake is probably mediated by the ingredient eritadenin. Studies show that this active ingredient has a positive effect on total cholesterol levels via the phospholipid metabolism of the liver, increases HDL cholesterol and is also involved in methionine metabolism.^13,14,15
 

The extract AHCC (Active Hexose Correlated Compound) obtained from Lentinula edodes, with its high content of alpha-glucans and other immunomodulating polysaccharides, is increasingly becoming the focus of clinical studies and is also showing scientific relevance in human papillomavirus (HPV) infections. In a randomised controlled trial, daily administration of AHCC over a period of six months resulted in elimination of HPV infection in 63.6% of 22 subjects with two-year persistent HPV infection of the high-risk type, while only two of the 19 subjects in the placebo group had a negative HPV result.¹⁶  
 

The use of Lentinula edodes in cancer therapy has been proven in practice and confirmed by studies. In addition to the immune defence directed against the tumour, an essential mechanism of action in adjuvant cancer therapy, the shiitake-born lentinians also inhibit tumour growth.^17,18 In vivo, the administration of an aqueous shiitake mycelium extract in rats with renal cancer led to dystrophic changes in the tumour cells as well as to tumour necrosis. Lentinula edodes also showed cytotoxic effects in in vitro studies with the human lung adenocarcinoma cell line A549 and the human laryngeal carcinoma cell line HEp-2.¹⁹ Initial pilot studies with the beta-glucan Lentinan isolated from shiitake also show that it improves certain immune parameters of chemotherapy patients, reduces the side effects of therapy and thus leads to a better quality of life.^20,21
 

¹ Dermiki, M. et al. 2013. Contributions of non-volatile and volatile compounds to the umami taste and overall flavour of shiitake mushroom extracts and their application as flavour enhancers in cooked minced meat. Food Chem. 141(1):77–83.
² Rahman, M. A. et al. 2018. Lentinula edodes (shiitake mushroom): An assessment of in vitro anti-atherosclerotic bio-functionality. Saudi J Biol Sci. 25(8):1515–23.
³ Bao, X. F. et al. 2002. Structural features of immunologically active polysaccharides from Ganoderma lucidum. Phytochemistry. 59(2):175–81.
⁴ Zhang, J. et al. 2002. Activation of B lymphocytes by GLIS, a bioactive proteoglycan from Ganoderma lucidum. Life Sci. 71(6):623–38.
⁵ Hsu, H. Y. et al. 2008. Reishi immuno-modulation protein induces interleukin-2 expression via protein kinase-dependent signaling pathways within human T cells. J Cell Physiol. 215(1):15–26.
⁶ Ma, C. et al. 2008. Differential protein expression in mouse splenic mononuclear cells treated with polysaccharides from spores of Ganoderma lucidum. Phytomedicine. 15(4):268–76.
⁷ Chen, S. D. et al. 2008. Effects of fermentation products of Ganoderma lucidum on growth performance and immunocompetence in weanling pigs. Arch Anim Nutr. 62(1):22–32.
⁸ Zhang, Y. et al. 2008. Effect of Ganoderma lucidum capsules on T lymphocyte subsets in football players on "living high-training low". Br J Sports Med. 42(10):819–22.
⁹ Anwar, H. et al. 2019. Shiitake Culinary-Medicinal Mushroom, Lentinus edodes (Agaricomycetes), Supplementation Alters Gut Microbiome and Corrects Dyslipidemia in Rats. Int J Med Mushrooms. 21(1):79–88.
¹⁰ Wachtel-Galor, S. et al. 2004. Ganoderma lucidum („Lingzhi“), a Chinese medicinal mushroom: biomarker responses in a controlled human supplementation study. Br J Nutr. 91(2):263–9.
¹¹ Handayani, D. et al. 2014. A high-dose Shiitake mushroom increases hepatic accumulation of triacylglycerol in rats fed a high-fat diet: underlying mechanism. Nutrients. 6(2):650–62.
¹² Shimizu, T. et al. 2018. Effects of Dietary Intake of Japanese Mushrooms on Visceral Fat Accumulation and Gut Microbiota in Mice. Nutrients. 10(5). pii: E610.
¹³ Asada, N. et al. 2019. Effects of Shiitake Intake on Serum Lipids in Rats Fed Different High-Oil or High-Fat Diets. J Diet Suppl. 16(3):345–56.
¹⁴ Yoon, K. N. et al. 2011. Antihyperlipidemic Effect of Dietary Lentinus edodes on Plasma, Feces and Hepatic Tissues in Hypercholesterolemic Rats. Mycobiology. 39(2):96–102.
¹⁵ Martin, K. R. 2010. Both common and specialty mushrooms inhibit adhesion molecule expression and in vitro binding of monocytes to human aortic endothelial cells in a pro-inflammatory environment. Nutr J. 9:29.
¹⁶ Smith, J. A. et al. 2022. AHCC® Supplementation to Support Immune Function to Clear Persistent Human Papillomavirus Infections. Frontiers in Oncology. 12:881902.
¹⁷ Ng, M. L., Yap, A. T. 2002. Inhibition of human colon carcinoma development by lentinan from shiitake mushrooms (Lentinus edodes). J Altern Complement Med. 8(5):581–9.
¹⁸ Ina, K. et al. 2013. The use of lentinan for treating gastric cancer. Anticancer Agents Med Chem. 13(5):681–8.
¹⁹ Vetchinkina, E. et al. 2016. Antitumor Activity of Extracts from Medicinal Basidiomycetes Mushrooms. Int J Med Mushrooms. 18(11):955–64.
²⁰ Ostadrahimi, A. et al. 2014. Effect of Beta glucan on quality of life in women with breast cancer undergoing chemotherapy: a randomized double-blind placebo-controlled clinical trial. Adv Pharm Bull. 4(Suppl 1):471–7.
²¹ Kataoka, H. et al. 2009. Lentinan with S-1 and paclitaxel for gastric cancer chemotherapy improve patient quality of life. Hepatogastroenterology. 56(90):547–50.
²² Avinash, J. et al. 2016. The Unexplored Anticaries Potential of Shiitake Mushroom. Pharmacogn Rev. 10(20):100–4.17) Ng, M. L., Yap, A. T. 2002. Inhibition of human colon carcinoma development by lentinan from shiitake mushrooms (Lentinus edodes). J Altern Complement Med. 8(5):581–9.

References Interactions
Stargrove, M. B. et al. 2008. Herb, Nutrient and Drug Interactions: Clinical Implications and Therapeutic Strategies. Mosby Elsevier, St. Louis, Missouri. 1. Auflage.
Gröber, U. 2011. Mikronährstoffe: Metabolic Tuning – Prävention – Therapie. WVG Wissenschaftliche Verlagsgesellschaft Stuttgart. 3. Auflage.
Gröber, U. 2014. Arzneimittel und Mikronährstoffe: Medikationsorientierte Supplementierung. WVG Wissenschaftliche Verlagsgesellschaft Stuttgart. 3. Auflage.