I am using the Now Foods E-400 with Mixed Tocopherols, and have generally like their products over the years. 750g of raw spinach would get you about 15mg of vitamin E. (Have a play on myfooddata). It is not clear that high doses cause cancer, they just associate with some kinds. It could be that people consuming large amounts are also consuming a lot of seeds and all of the linoleic acid and cyanogenic glycosides (or whichever toxins) that come along for the ride. They could be punishing sunflower seeds, and sunflowers love accumulating heavy metals. It could also be downstream of dampening too much oxidation and confusing signalling, but I am just speculating all over the place here.