A May 2017 study of white button, shiitake and oyster mushrooms has shown that:

“Microwaving and grilling are the best processes to maintain the nutritional profile of mushrooms”

“Mushrooms are considered valuable health foods, since they have a significant amount of dietary fibre and are poor in calories and fat.”

“They have a good protein content (20-30% of dry matter) which includes most of the essential amino acids; also provide a nutritionally significant content of vitamins (B1, B2, B12, C, D and E) and trace minerals such as zinc or selenium.”

“Mushrooms are also an important source of biologically active compounds with potential medicinal value such as beta glucans.”

“A little oil portion while grilling mushrooms is not a problem. This minimal amount will not cause nutrient loses by leaching; in fact, the antioxidant capacity can be even improved.”

“If olive oil is used, the fatty acid profile of the final preparation is enhanced with barely [any] increase in the calorie content."

"Frying and boiling treatments produced more severe losses in proteins and antioxidants compounds, probably due to the leaching of soluble substances in the water or in the oil, which may significantly influence the nutritional value of the final product"