The most commonly consumed mushroom in the United States is Agaricus bisporus or the white button mushroom. A. bisporus has two other forms - Crimini or brown mushrooms with a more earthy flavor and firmer texture, and Portabella mushrooms with a large umbrella-shaped cap and meaty flavor.
All three mushrooms, but especially the fresh button mushrooms, possess substances that inhibit the activity of aromatase (an enzyme involved in estrogen production), and 5-alpha-reductase (an enzyme that converts testosterone to DHT). The latest findings show that white button mushrooms can reduce the risk of breast cancer and prostate cancer. An extract of white button mushrooms decreased cell proliferation and decreased tumor size in a dose-dependent manner. The chemoprotective effect can be seen with an intake of about 100 grams (3.5 ozs) of mushrooms per day.