When you're trying to lose weight, calories are the name of the game. And mushrooms provide a big blast of deliciousness for very few calories. When watching your weight, it's important to take out the fat, not the flavor.
Mushrooms are standard fare in Asian cultures, and Americans are learning to appreciate them for their texture and flavor. They are low in fat and sodium, and they contain a super-powerful flavor enhancer called glutamic acid, the same amino acid (a building block of protein) found in MSG (monosodium glutamate). Besides lending wonderful flavor to foods, mushrooms contribute more nutrition than you might think.
Mushrooms provide an unusual array of nutrients, not unlike those in meat, making them a particularly appropriate food for vegetarians. Cooked mushrooms are an unexpected protein source, which, even though incomplete, is easily complemented by grains. They also shine in iron, riboflavin, and niacin; offer decent amounts of potassium, selenium, copper, and zinc; and they are full of fiber.
Selenium is helpful for the body's glutathione peroxidase, which is a potent antioxidant. Another powerful antioxidant, a phytochemical called L-ergothioneine, is plentiful in portabella and crimini mushrooms (crimini are a common, brownish variety of button mushrooms) and is not destroyed by cooking.
When possible, stick to cooked mushrooms. They're higher in nutrients than raw mushrooms; for the same volume, you get two, three, or even four times the nutrients. That's because cooking removes water from mushrooms, concentrating nutrients and flavor. Moreover, hydrazines, which are toxic natural compounds in raw mushrooms, are eliminated when mushrooms are cooked or dried.
Some researchers have found that cooked enoki, oyster, shiitake, pine, and straw mushrooms, as well as the more popular button mushrooms, have antitumor activity. Wood-ear mushrooms exhibit blood-thinning properties that may help prevent the dangerous clotting that contributes to heart disease.