New data show that mushrooms retain most nutrients after they are cooked.

Recent USDA-ARS research indicates that mushrooms contain several key nutrients, including copper, potassium, folate and niacin. Investigators examined several varieties of mushrooms--white button, oyster, shiitake, enoki, portabella, crimini and maitake--to create a unique nutrient profile for each.

Scientists collected mushrooms from retail outlets across the United States to get a nationally representative sampling. The mushroom varieties were analyzed to determine their amount of fat, fiber, protein, carbohydrate, vitamins and minerals, and ergosterol, a precursor to vitamin D.

While most varieties were analyzed in their raw state, white button mushrooms, which are commonly used in recipes, were also analyzed after they were stir-fried and microwaved to gauge the levels of nutrients retained after cooking. Adding to existing data, portabella mushrooms were analyzed after they were grilled, and shiitake mushrooms were analyzed after they were stir-fried.

Most nutrients were found to be fully retained when the product was cooked, while others were retained after cooking at between 80% and 95% of their levels in the raw mushrooms. All of the mushrooms provided a significant amount of copper. Each cup of stir-fried white button mushrooms provided 0.3 mg of copper, which is about one-third of the recommended daily intake for adults. Copper helps the body produce red blood cells and drives a variety of chemical reactions that are key to human health.

The mushrooms also provide a significant amount of potassium, a mineral that helps the body maintain normal heart rhythm, fluid balance, and muscle and nerve function. Two-thirds of a cup of sliced, grilled portabella mushrooms contains the same amount of potassium as a medium-sized banana.

The new nutrient values for mushrooms will appear in this year's update to the ARS' Nutrient Data Laboratory-managed USDA National Nutrient Database for Standard Reference, Release 19. It will be available soon at www.ars.usda.gov/nutrientdata.

In other USDA-ARS research, scientists are determining how different strains of shiitake mushrooms and growing media affect mushroom growth.

Further information. David Haytowitz, USDA-ARS Nutrient Data Laboratory, Building 005, Room 105 BARC-West, Beltsville, MD 20705; phone: [phone]; fax: [phone]; email: [e-mail].