The "intrusive elements" of a liver flush are grapefruit juice and olive oil, plus epsom salts to relax the bile ducts. The concept is based on an old eastern european remedy for helping pass gallstones.

I've done it 3 times, each time with increasingly dramatic results.
The recipe at that site is far more complex that it has to be -- simply eat no fat all day, no food/drink after lunch and only limited water (for thirst relief), take your doses of epsom salts, and drink the juice/oil combo at bedtime at it will work fine. It doesn't have to be olive oil ahnd it doesn't have to be grapefuit juice, although a citrus juice will work best. (The original recipe to help pass stones says to stay up and walk all night.)

It's both yuck and wow; very little chance of causing any harm and it does indeed have some dramatic effects afterward. I suggest an enema the evening before starting however -- it'll make the flush easier and reduce the yuck. If you are habitually bloated or retaining water, this can really help get rid of it and jump start weight loss. Drink lots of water the next day; you'll be a bit underhydrated afterwards.

Does it actually cleanse the liver? I have no idea; I certainly don't buy the parasite stuff. But it dies work better than either just an enema of a short fast or both together.