The King Oyster Mushroom is low in calories and high in protein. Fresh mushrooms contain 3 percent to 21 percent carbohydrates and 3 percent to 35 percent dietary fiber on a dry-weight basis. Mushrooms also contain a number of essential minerals such as phosphorous, potassium, calcium and iron. They are also an excellent source of thiamin, riboflavin, niacin, biotin and ascorbic acid.

Anti-Cancer Qualities
Richard Sullivan, a member of the Division of Cancer Studies, wrote in an article titled Medicinal Mushrooms that various Pleurotus species, such as eryngii, might be associated with anti-cancer activity, positive effects on the immune system, and anti-viral, antibiotic and anti-inflammatory activities. This might be due, in part, to a key active compound found in king oyster mushrooms known as beta-glucans.

Antioxidants
King oyster mushrooms have high antioxidant content. Antioxidants are found in foods and help to combat harmful and cancer-related chemicals known as free radicals. King oyster contains an antioxidant amino acid called ergothioneine, which is stored in higher concentration in organs exposed to oxidative stress such as the kidney, liver and the eyes.

Blood Cholesterol
King Oyster mushrooms produce compounds known as statins. These drugs stimulate receptors in the liver to help clear low-density lipoproteins from the body. Lovastatin is a chemical specific to the king oyster mushrooms, according to TodaysDietitian.com. Lovastatin may reduce cholesterol in the blood and promote vascular health.