Mushrooms are about 80 percent water by weight, but the remaining 20 percent is packed with nutrients. One medium portabello mushroom has more potassium than a banana, and a 1/2-cup serving of most mushrooms has 20 to 40 percent of the daily value of copper, a mineral with cardioprotective properties.
Mushrooms are the only plant food that contains vitamin D. Shiitakes are the highest, with one cup yielding about 12 percent of the recommended daily value.
Shiitakes also contain lentinan, a polysaccharide (large carbohydrate) that boosts the immune system. Popular button mushrooms, have phytochemcials that inhibit the activity of aromatase, and thus have a role in breast cancer prevention in postmenopausal women. Rounding out the phytochemical trio are triterpenes, steroid-like molecules that inhibit histamine release and have anti-inflammatory properties.
All this nutritional firepower comes in an easy-on-the-waistline form: One cup of mushrooms has only 15 calories.
-from Sheah Rarback's column in today's Miami Herald.