Originating from East Asia, shiitake are often found in oriental dishes. They offer a distinct flavor which is unlike button, crimini, and portobello. They are the 2nd most popular mushroom worldwide (the common white button is the 1st).If you look at the nutrition facts for shiitake, they offer some unique benefits, especially when it comes to their mineral content. One cup cooked (145 grams) provides you with 36 mcg of selenium, which is 51% of your daily value, 1.3 mcg of copper (65%), 0.3 mcg of manganese (15%), 1.9 mg of zinc (13%) and under 10% for iron, magnesium, phosphorus, potassium, and calcium.Like most mushrooms, they don't contain many vitamins. The exception is pantothenic acid (vitamin B5) which comes in at 52% of your daily value. The rest are in much smaller quantities; under 15% for riboflavin, niacin, vitamin B6, folate, thiamine, and under 1% for vitamins A, C, E, K, and B12.Mushrooms are often associated as being a good source of vitamin D but that is not true. If and when they are exposed to UV light, it is true that they naturally produce vitamin D, but in the form of D2 (ergocalciferol/viosterol) and not D3 (cholecalciferol). The difference between them is that vitamin D2 is the plant form and according to The American Journal of Clinical Nutrition it "should not be regarded as a nutrient suitable for supplementation or fortification" (1). This it not news, but old knowledge, which makes it especially deceptive that some mushroom packages and their sellers continue to perpetuate the myth that the vitamin D they contain is bioavailable to humans when it is not.Do shiitake mushrooms contains many antioxidants? Not really. Their ORAC of 752 far below most fruits and vegetables. Though this aspect applies to almost all mushrooms consumed for food; the highest is raw portobello at 968 and the lowest is oyster at 664. Even though the former is almost 50% higher than the latter, both of these numbers are low and therefore mushrooms should not be viewed as a good source of antioxidant content. The exception is concentrated chaga extract but that costs around $100 for 100 grams (3.5 ounces). For this reason, the primary health benefits of shiitake and other fungi are their mineral content and phytonutrients, not antioxidants.Are the stems of shiitake mushrooms edible? Many people are under the assumption they are poisonous and should not be eaten, but that's just not true. The stems are safe to eat, including those coming from dry mushrooms. The reason it is advised not to eat them has nothing to do with toxicity, but rather how fibrous they are. Unlike most other forms of fungi, the stems of shiitake can be extremely tough and leathery. For this reason if you are going to consume them, at the very least, cook or boil them for an extended period of time. You also probably wouldn't want to eat too many at a time since their toughness can lead to stomach aches. Those with any kind of GI motility issues should probably avoid the stems altogether. Whether you eat them or take them off and throw away, the choice is yours because technically, they are edible even if they're not the most pleasurable to eat.
USDA Database for the Oxygen Radical Absorbance Capacity (ORAC) of Selected Foods, Release 2 - Prepared by Nutrient Data Laboratory, Beltsville Human Nutrition Research Center (BHNRC), Agricultural Research Service (ARS), U.S. Department of Agriculture (USDA) - May 2010