Beat me to it, although I was going to say go the whole nine yards and get the colonoscopy, too
I'm at that age, so I asked a few friends about it. You're spot-on, cause the consensus is that the prep is the really unpleasant part, not the actual procedure. So, if you're going to cleanse, get the colonoscopy, and at least you will be doing SOMETHING good for you.
You do NOT have a "half inch of spackle" inside your colon. (Contrary to the assertions in a popular late-night U.S. infomercial...)
The fad is nonsense still hanging around from the turn of the century. That is, the LAST century. Apparently, it become popular in the early 1900's, and has since been throughly debunked by medical research and our understanding of physiology.
I'm curious as to whether this is as popular in continental Europe, which has much tighter control over over-the-counter "holistic" medicines and supplements. (In the U.S., we have practically none, and it's big business with the center section of Whole Foods Market turned into a bazaar of the bizarre, at outlandish prices to boot.)
I tend to go with the recommendations and opinions of the Center for Science in the Public Interest (CSPI), which publishes the Nutrition Action newsletter. They are the organization most responsible for getting our food labeling laws updated (for example, most recently, to get labeling of trans-fats.) They are also hugely in favor or regulating supplements, etc. more in the manner that Germany does.
They say it's nonsense.