Hericium erinaceus  triggers neurite outgrowth and regeneration of damaged nerves

The culinary mushroom that has been extensively studied for its neurohealth properties is   H. erinaceus(Lion's Mane mushroom). The polysaccharides in an aqueous extract of the Lion's mane mushroom could induce neuronal differentiation and promote neuronal survival.[ 10] The chemical profile of extracts of this mushroom has been actively studied and reported by Kawagishi and co-researchers. Extracts of   H. erinaceus  induced the expression of neurotrophic factors such as NGF in astrocytes.[ 11, 12]

In their studies, hericenones were isolated from the fruiting bodies of Lion's mane while erinacines were isolated from the mycelium of the mushroom. Endoplasmic reticulum stress - attenuating compounds and dilinoleoyl phosphatidylethanolamine, a phospholipid with linoleic acid, an unsaturated fatty acid, purified from extracts of dried fruiting bodies of   H. erinaceus, reduce endoplasmic reticulum stress-induced cell death. This may reduce the risk of neurodegenerative disease-induced cell death.[ 13] Fujiwara   et al.[ 14] investigated the neuroprotective effect of   H. erinaceus  on the ischemic brain damage in a middle cerebral artery occlusion model in mice.   Hericium erinaceus  (300 mg/kg, continuously fed for 14 days after surgery) significantly decreased the size of the cerebral infarcts one day after the occlusion. In another study, a double-blind trial was conducted with 50- to 80-year-old Japanese men and women diagnosed with mild cognitive impairment in order to examine the efficacy of oral administration of   H. erinaceus, for improving cognitive impairment, using a cognitive function scale based on the revised Hasegawa Dementia Scale (HDS-R).[ 15] The subjects in the   H. erinaceus  group took four 250 mg tablets containing 96% of Yamabushitake dry powder three times a day for 16 weeks. Cognitive function scale scores increased with the duration of intake.

Laboratory tests showed no adverse effect of   H. erinaceus. The study suggested that   H. erinaceus  is effective in improving mild cognitive impairment.[ 15] Extracts of   H. erinaceus  induced phosphorylation of c-Jun N-terminal kinase (JNK) and its downstream substrate c-Jun, and increased c-Fos expression, suggesting that   H. erinaceus  promotes nerve growth factor gene expression   via  JNK signaling.[ 16] Furthermore, the efficacy of   H. erinaceus   in vivo  has been examined. Mice given feed regime containing 5% (w/w)   H. erinaceus  dry powder for seven days showed an increase in the level of NGF mRNA expression in the hippocampus.[ 16]

These studies are very encouraging, and the consumption of   H. erinaceus-fresh or processed is acceptable. There are many preparations available off the counter. However, there should be guidelines and monitoring to ensure safety, efficacy, and other parameters to ensure that these preparations are functional as claimed. The best option will be consumption of fresh mushrooms. The processing has been reported to affect the neurite stimulatory activity of   H. erinaceus.[ 17, 18] Cultivation techniques and conditions may affect the medicinal properties of mushrooms too. Though   Hericium erinaceus  is a temperate mushroom, it can be cultivated in Malaysia, a tropical country.

CONCLUSION

The studies done by many researchers as well as on-going studies show that selected mushrooms do have neurotrophic properties that can be beneficial to humans. Regular consumption may promote nerve and brain health. This is particularly useful during injury (as in an accidents) or as we age. Further, there is a need to study the potential mushrooms to elucidate their mechanisms of activities as well as clinical trials. This far, only   H. erinaceus  has been extensively studied. The identification of more varieties of mushroom with these unique properties may contribute to identifying novel chemical agents that can have preventative or therapeutic functions.