Shiitake

Shiitake is notable for FODMAPs, sorbitol, histamine, tyramine and salicylate. Clear on sucrose, lactose, oligosaccharides, fructose, nickel, oxalates and gluten.

Yes — shiitake is high in FODMAPs. Shiitake is used for umami as much as for substance, and dried shiitake is steeped to make broth - which puts the mannitol straight into the liquid everyone drinks. A dashi built on shiitake is the highest-exposure form of this mushroom, higher than eating the caps.

Yes — shiitake is high in sorbitol. Shiitake carries the heaviest polyol load of the common mushrooms, mannitol above all, and drying concentrates it further. Dried shiitake is the form most likely to cause trouble.

Shiitake contains only low levels of histamine. Shiitake is low when fresh, and that qualifier does more work here than usual. Mushrooms are mostly water and spoil from the inside, and it is that spoilage that builds histamine; a fresh one is low, one that has darkened in the fridge is not. Dried mushrooms have spent weeks doing exactly what drying does.

Shiitake contains only low levels of tyramine. Shiitake is low in tyramine fresh. Mushrooms have been surveyed processed and unprocessed, and it is the processing that moves them - dried, pickled or left to darken, they carry more than they did in the punnet. Amounts vary by brand and recipe, so always check the label of the exact product.