Mushrooms are fungi, not plants, and the place that difference shows up nutritionally is vitamin D. Shiitake contains the precursor ergosterol, which converts to vitamin D2 on exposure to ultraviolet light.
It is the same principle by which cholesterol in human skin becomes vitamin D3. Spreading dried shiitake in sunlight for thirty minutes to two hours multiplies its vitamin D content.
Key benefits
Beta-glucans modulate the immune response
Shiitake's beta-glucans, lentinan among them, bind receptors on immune cells and modulate their response. Purified lentinan has been used in Japan as an adjunct therapy.
Sun-dried, it becomes a vitamin D source
UV-exposed shiitake can reach tens of micrograms of vitamin D per 100 g. Mushrooms are effectively the only non-animal food carrying vitamin D, which matters a great deal in plant-based diets.
Strong umami for the calories
It is rich in guanylate, an umami compound, so dishes taste complete with less salt. That makes it a practical tool in a low-sodium diet.
There is research on cholesterol
Animal studies suggest shiitake's eritadenine affects cholesterol metabolism. Human evidence remains limited, so it is too early to state this as established.
How to eat it well
- Spread them in sunlight for at least 30 minutes before cooking. Dried or fresh, vitamin D rises. Gills facing up is more efficient.
- Do not discard the soaking water from dried shiitake. The umami compounds are dissolved in it.
- Cooking with oil improves absorption of vitamin D and other fat-soluble components.
- Always cook fresh shiitake. Raw consumption is rarely linked to a distinctive dermatitis.
- The stems are tough but perfectly usable chopped fine for stir-fries or stock.
What to watch out for
- Eating raw or undercooked shiitake occasionally causes shiitake dermatitis, a whip-like rash. Cooking it through prevents this.
- Relatively high in purines, so consider the amount if you have gout.
- Avoid with mushroom allergy.
- On immunosuppressants, discuss high-dose mushroom extract supplements with your clinician. Culinary amounts are usually fine.
- Because dried shiitake substitutes umami for salt, you generally need less seasoning alongside it.
Nutrition
Approximate values per 100 g edible portion.
- Calories
- 34 kcal
- Carbohydrates
- 6.8 g
- Fiber
- 2.5 g
- Protein
- 2.2 g
- Selenium
- 5.7 µg
- Copper
- 0.14 mg
- Vitamin B3
- 3.9 mg
- Potassium
- 304 mg
Key nutrients
- Beta-glucan
- Vitamin D
- Fiber
- Selenium
- Copper