They may not be nature's most beautiful creation, but they're nutritional powerhouses and a great addition to a healthful diet. We're talking about mushrooms, which come in many varieties, are extremely versatile, and are popular in many different cuisines. They're low calorie, contain no fat or cholesterol, and have almost no sodium. Whether you've never had them or they're a centerpiece of your diet, there's a lot to learn--and love--about this fabulous food.

Vitamin D

According to the Mushroom Council, mushrooms are the only natural fresh vegetable or fruit that contains Vitamin D. Four or five white button mushrooms normally provide 15 IU of Vitamin D, but research suggests that exposing mushrooms to the ultraviolet rays found in sunlight may boost Vitamin D levels from 15 IU to 400 IU, the recommended daily amount. Scientists are working on ways to make light-enhanced mushrooms available to the public. Meanwhile, since few other foods contain Vitamin D, it's worth having a handful of mushrooms with your meal.

Other vitamins and nutrients found in mushrooms include:

Riboflavin. Helps keep your body's red blood cells healthy.

Niacin. Keeps skin healthy and your digestive and nervous systems working well.

Pantothenic acid. Helps with hormone production and regulates the nervous system.

Selenium. An antioxidant that protects against cell damage, boosts the immune system, and promotes male fertility.

Copper. Makes red blood cells and bolsters bones and nerves.

Potassium. Maintains mineral and fluid balances in the body, and helps control blood pressure.

The white button mushroom is the country's most popular, accounting for 90 percent of mushroom sales. You can eat them raw, but many people prefer them sautéed with meats and grains, cooked into sauces, or baked into pizzas. Cremini mushrooms can be used in the same ways, although they have a stronger, earthier flavor than white mushrooms do. Large portabella mushrooms are popular sliced, cooked, and eaten on a bun for a meaty-tasting sandwich without the meat, while enoki mushrooms are often found in Asian dishes. Other popular varieties are oyster, maitake, and shiitake mushrooms.

Some people enjoy picking their own mushrooms, which grow wild in many areas. But be warned: Certain varieties of mushrooms are toxic, causing permanent organ damage or death if eaten. They're not always easily distinguishable from harmless mushrooms, so it's best to leave the picking to those with special training.