DE was originally given the designation "food grade" by the government because DE was mixed with grains in storage bins to help keep it dry and as an insecticide. That's where the term "food grade" came from. It was never intended to be eaten, only used as a drying agent/insecticide.
DE is ineffective when wet, until it dries. It is not a worm preventative nor a wormer. It is wet inside chickens innards, as all mammals, including humans, therefore it is ineffective.
DE can kill insects as a drying agent. It has never been proven to do anything else.
DE is 90% silica, the most common mineral in the earth's crust. There is nothing nutritional about DE, it is indigestable, It cannot benefit the body in any way and there's no scientific evidence to prove it.
DE is hyped for sales purposes.
If you decide to purchase it for what it is intended to do; help keep coops dry, a preventative for lice/mites, keeping feed dry from moisture...then you've gotten your money's worth. Anything else is a waste of time and money with this product.
For safety reasons regarding INHALING DE... I refer this link again:
http://www.cdc.gov/niosh/docs/81-123/pdfs/0552.pdf