In short, all detox is quackery ("detox" as a term for alcohol and drug rehabilitation excepted.)
Let's get right down to facts - there is no evidence that today we are living in a toxic environment, and that almost everything we eat is awash with these "toxins." There is also no evidence that these "toxins" stay in the body indefinitely (the liver and kidneys do a pretty good job of flushing most toxic substances out - heavy metals aside, that is), and there's no evidence that eating the "right" stuff can automagically scrub these toxins away.
The body is pretty good at detoxifying itself, you see. You have a liver that already does that and does it admirably. You have kidneys that do the same but with liquids, broadly speaking. These two items are more than capable of filtering out most everyday toxins that actually get into your body. Obviously I'm not saying that they can render you immune to VX gas or enable you to survive taking a good hefty belt from a tub of hydrogen cyanide, and there are certainly substances - mainly heavy metals - that do build up in the body, but unless you're going out your way to consume such items, you'll be just fine with what the Gods gave you. And as long as you don't drink yourself to death every day, in which case you may pickle your liver, but that's just sound common sense really.
Proponents of detox products usually point to how, nowadays, we're allegedly living in an intrinsically toxic environment. They claim air pollution, preservatives and pesticides in food, and in some cases, electro-magnetic radiation, is all around us and our bodies can't cope on their own any more, which is responsible for all our problems. Hmmm. I'm sorry, but this doesn't wash. Maybe it might in, say, Soviet-era industrial centres, but then again, it's allegedly economically viable to refine the soil in Norilsk because it's so full of heavy metal deposits from the old ore refinement plants.
Therefore, if anyone suggests you need to detoxify for whatever reason, or "detox" for short, they're either I. deluded, II. terminally thick, or III. trying to sell you some expensive rubbish you don't need. Most likely the latter. This is not, of course, to say that you can't benefit from not bingeing on Ghetto Burgers, cutting out the fags, and eating more fresh fruit and veg. Just that you don't have to spends £lotsofmoney on ridiculous "health food" or other godawful nonsense - the only thing it's truly healthful for, of course, is the bank balance of the retailer.
So why, then, if it is demonstrable woo, do people fall for it?
Well, my theory is this. It is a form of expiation if you will. The people who this is marketed to are folks from marketing demographics ABC1, who spend most days noshing their heads off on hastily-guzzled bowls of cereal in a morning, loads of caffeinated liquids at work, and huge grease-outs for dinner in the evening, and at weekends, lots of alcohol and chips and gravy or Meatball Marinara afterwards to soak it up, and have limited time or arsedness for physical activity after work. So in lieu of moving around a lot because their jobs involve being sat on their best features, they feel - or are conditioned to feel by the marketrons that peddle this bollox - guilty. They then look around for explanations. However, a visit to their GP as to why they feel so shite would result in advice such as, "work less, drink less, cut out the fags, fewer pies and pasties, more exercise, and everything will return to normal." But they can't do that. If they worked less they'd not get that massive pay rise that they're worth. If they drank less they'd be seen as boring at company team-building events. And so on. But "detoxing" provides both a scientific sounding explanation for why they feel this way and a scientific-sounding way in which they can combat it. So they sign up as a form of mortifying the flesh. After all, if things that are enjoyable (alcohol, big dinners, caffeinated soft drinks, fast cars, sex, chocolate, etc.) are bad for you, then evil-smelling lime-green liquid gack made of aduki beans, kale, wheatgrass, and acai berries must be divinely healthy. And besides, Gwyneth Paltrow (she's that actress who bullied actual authors out of a literary festival with her ghostwritten cookbook, if you must know) does it so and she looks like that at age 41 so something must be done right. Right?
So just as in past days people atoned for their sins by crawling over sharp gravel to touch a statue of the Virgin Mary which
had a rusty old water pipe running through the eaves above it cries blood for the sins of man, now they mortify the flesh for the sins of eating nice things by starving themselves two days a week and similar, and tend to say things like, "hunger is weight leaving the body."
Which tells you what sort of mentality we are dealing with here.