It seems what is lacking are the pre/post tests that are available for fuctional liver testing...I know that Great Smokies Lab and others Labs have a test that measures this, as well as how the liver breaks down estrogen, which would be an interesting testament to the Liver Flush or other detox methods.
There is a book I found written by two Naturopaths, one who has founded many of these tests with Great Smokies: http://www.detox.org/bennett.html
They don't talk about liver flushes, but have a very detailed section about impaired detoxification and how the various stages and areas of liver function can be impaired: very scientific! Loree