diatomaceous earth -- does it actually kill internal parasites?

What are the uses of Diatomaceous earth? I was led to believe that it will kill internal parasites - now I have been told that it won't.
What is the research? &/or theories behind it?

DE has several uses and it will kill internal parasites over a long period of use when mixed with feed.
Most of the negative press and comments are from people who think this is a fast acting cure all, it is not.
For internal parasite control you have to feed it to animals for a minimum of 30 days, 60 days is better.
For insect control the DE has to remain dry, it works by cutting through the cuticle of the insects shell (the waxy coating) thus dehydrating the insect.
It works on many pest insects. It is a good source of silica(necessary for uptake of many minerals, even in humans).
If it gets wet, it doesn't work for insect control. It will work again once it dries out.
It is a good soil amendment because it provides silica and a few trace minerals that the bacteria and fungi need.

Redhawk

I'm also very curious about the internal parasites claim, mainly because I don't understand it. By what means does it suppress or kill internal parasites?

For external uses, the means are mechanical- slicing through chitin, seeping bugly fluid out until the thing desiccates. That doesn't work if the DE is wet though, right? Which is definitely is if you take it internally...

And if there's some other manner by which it kills certain gut fauna, why doesn't it have a similar effect on soil fauna?

With internal parasites they have to ingest the DE, that's why you have to give it for such a long period of time.
I use pumpkin seeds for internal parasites (specifically worms), they work faster and more reliably for us than using De internally.
I use DE for the external insect pests in the garden, and as an element of compost for soil conditioning.
We also will occasionally use it on our foods (light sprinkle like it was salt) to make sure we get some silica in our systems, since it is important for certain nutrient uptake.

I know some people that use it far more than we do on Buzzard's Roost.
The bacteria of the gut actually break the silica of DE down so that they can use it for their needs.
These bacteria are then eaten by the fungi and from there it gets into the plant roots.

Yes, wet DE is ineffective DE, it only works for desiccation when it is dry, internally it is more a source of silica.
If you want to see how it works when wet, get a piece of wood and use it like it was a sanding medium, it will, when wet, put a nice polish on hardwoods, lots of elbow grease will be required.
I use it as a final polish for French polishing guitars, it works a lot like super fine pumice for that purpose.

So it is healthy for the soil?
I was worried about it killing earthworms etc
I use it in the chicken run were I get nice compost...

In a trial I did on DE as a soil amendment in a garden plot, there was no apparent damage to earthworms or nematodes.
In a secondary trial I found that the soil bacteria surrounded the particles and broke them down, it seems the bacteria use the silica as a source of food.

Another use for DE, ...We had a Wwoof'er staying here one time. She opened one of the bedroom windows without a screen in it. A bat flew in. After she spent a certain amount of time screaming, I caught it with a blanket, and I threw blanket and bat outside. The next morning she brought her blanket back inside, without checking first. Unfortunately a couple of bat bugs had overnight transferred to the blanket, which in her inexperience she hadn't accounted for happening. Two nights later she started to get bit. She thought we had bed bugs. We didn't, we now had bat bugs, ...which are very similar. We tossed the rug, washed the sheets and used DE around the floor boards. Worked great (and the whole incident helped the wwoof'er to find her way back to California). Moral of the story is: Wwoof'ers come and go, but DE will always be your friend. We also very occasionally use DE on garden bugs, but very rarely. Our soil is so good and plants so happy that it's been years since any bug problem. It's kinda funny to me that back in the 60's the better informed, health food store hippies thought DE would kill you, ...like eating glass. Now the same (now old timers) recommend it for internal use. Which is another way of saying, Beware of current orthodoxy.