Nuts in general have been found to be good for our health. However pistachios in particular because of the presence of gamma-tocopherol which is a form of vitamin E have been found to be of particular benefit in the reduction of some cancers. 

"Vitamin E is made up of a variety of fat-soluble vitamins, including gamma-tocopherol, that perform many functions in the body. Vitamin E-rich foods act as antioxidants, helping to prevent damage from free radicals, protect skin from ultraviolet light, and allow for proper cell communication.
"Pistachios are not only a good source of vitamin E, but are rich in B vitamins -- specifically B6, which is great for the nervous system and helps to promote proper breakdown of sugars and starches," You can read the full article here.