Shiitake

East Asian mushroom with a firm bite and deep umami. Cook fresh in a pan, wok or oven; dried in stocks and stews. Cook it through: raw, it can cause a rash.

What is shiitake? From the wok to the lab

You’ll find it in supermarkets and Asian restaurants all over the world: shiitake (Lentinula edodes), with its meaty brown cap and very leathery stem. After the common cultivated button mushroom, it’s the second most widely grown mushroom on the planet. Its high glutamic acid content gives it such a deep, meaty umami that it can carry an Asian broth on its own. What many home cooks don’t know: this humble kitchen mushroom is one of the most researched mushrooms in medicine. For decades, researchers in Asia have used shiitake as a source for isolating complex compounds studied in cancer treatment.

What’s in the thick cap

Besides a good amino acid profile for a vegetarian food and the unusual fact that shiitake dried in the sun can build up plenty of vitamin D2 (ergocalciferol), one polysaccharide gets most of the scientific attention:

• Lentinan: A tightly structured 1,3-beta-D-glucan isolated from shiitake. In Japan, purified lentinan has been officially approved since the mid-1980s as a drug given alongside standard treatment for advanced stomach and bowel cancer. That’s a purified medicine – not something you get from a mushroom stir-fry.
• Eritadenine: A small compound that, in studies, reduced cholesterol levels in the blood by acting on an enzyme.

What studies look at: white blood cells

AHCC and natural killer cells

In biohacking circles you’ll often come across a mysterious acronym, promoted against seasonal colds and stubborn viral infections such as Epstein-Barr: **AHCC** (active hexose correlated compound). It’s a concentrated, fermented extract made mainly from the fibrous underground mycelium of shiitake. Double-blind, placebo-controlled studies at well-known US universities measured higher numbers and activity of natural killer cells (NK cells) and macrophages in the blood of people taking AHCC. These white blood cells patrol the body for abnormal and infected cells and release proteins called perforins to break them down. Keep in mind: AHCC is a supplement extract, so these results say nothing about eating shiitake.

Eritadenine and cholesterol

In rodent studies, raw shiitake largely prevented the steep rise in cholesterol caused by a very high-fat diet. Eritadenine inhibits an enzyme in the liver involved in building and remodelling blood cholesterol, and in these animals it increased the amount of fat excreted via the gut. These were animal studies.

Kitchen tip: cook it, then sun it

Never eat the cap of a shiitake raw: in rare cases, the raw mushroom triggers an itchy rash that looks like whip marks (shiitake dermatitis). Cook it until soft. And before you use the often hard, dried shiitake from the Asian supermarket in your ramen, lay them in direct sunlight in the garden for two hours, gills facing up! Mushrooms behave a bit like human skin: UVB light from the sun makes them produce vitamin D within a few hours – and it ends up on your plate at dinner.