Vitamin E refers to a group of eight fat-soluble compounds that include both tocopherols and tocotrienols. Of the many different forms of vitamin E, γ-tocopherol is the most common in the North American diet. γ-Tocopherol can be found in corn oil, soybean oil, margarine and dressings. Researchers have identified an elusive anti-cancer property of vitamin E that has long been presumed to exist, but difficult to find. Many animal studies have suggested that vitamin E could prevent cancer, but human clinical trials following up on those findings have not shown the same benefits.