An overview of the lithium content and lithiation of the cultivable macrofungal species, Agaricus bisporus and Pleurotus spp.

Background: Lithium (Li) therapy has long been used as an effective treatment for bipolar affective disorders and research continues on its reported benefits in treating neurodegenerative brain diseases. However, it also elicits side-effects which may be related to the form and quantity of dosage. The mycelium and fruiting bodies of popular edible macrofungi, A. bisporus and P. ostreatus have shown promising results in the ability to enrich Li and could potentially serve as an alternative, more calibrated and bio-accessible source.  
Scope and approach: This review is focused to feature results from studies that have been carried out, both on the natural occurrence of Li in wild and cultivated common edible Agaricus spp. and Pleurotus spp. mushrooms as well as on the lithation of their mycelia and fruiting bodies.  
Key findings and conclusions: Lithium occurs ubiquitously in wild Agaricus and Pleurotus fungi at relatively low concentrations, typically ranging from < 0.02 to ~1.0 mg kg^{− 1} dry weight (dw). Cultivated, retailed specimens show similar (0.03–~0.5 mg kg^{− 1} dw) concentrations. In contrast, the lithiated mycelia of P. ostreatus achieved a maximum Li concentration of ~1600 mg kg^{− 1} dw, and the edible fruiting bodies of A. bisporus and P. ostreatus were found to be lithiated to levels of ~40 mg kg^{− 1} dw and ~10–~100 mg kg^{− 1} dw. The Li concentration of 38 mg kg^{− 1} dw achieved for A. bisporus using Li₂O compost fortification represents around 200 to 400-fold enrichment relative to the control or retail mushrooms. The process of compost fortification did not introduce contaminant elements such as Cd, Hg, Pb, above the regulation levels within the EU, or above those typically seen in the retail products. Such enriched mushrooms consumed as part of the diet, would allow a more controlled release of Li in the digestive system because of the longer digestion period (as compared to Li salts which are rapidly absorbed) which could potentially reduce or remove some of the side effects that have been reported. More targeted studies are required in order to clarify the absorption and pharmacokinetics of Li contained in these enriched mushrooms.