New studies show sticking a tube up what I had better call your back passage, flushing gallons of water into it, then, er … letting it all out again does not have miraculous health benefits. This news may not be as significant as the collapse of the global economy, but neither is it a total surprise. Both depend on sets of completely irrational beliefs.

I am no expert in the flushing out of debt from the rich to the poor, but I do unfortunately know something about the up-your-bum stuff. Colonic irrigation, now called colonic hydrotherapy (nicer and less agricultural?) was, like everything from IVF to Scientology, once only the province of wacky celebrities. Yet we are all, as Britney declared, Toxic. Modern life is rubbish. The idea that our bodies are festering with nastiness makes some sort of sense, though in my defence, I have always believed myself to be nothing without my toxins.

The idea of a detox has an appeal. Cut down the booze. Eat simply. Give your system a break; let your mind roam free. As we enter Ramadan, one sees in the cyclic nature of fasting and feasting something elemental. As children starve in Somalia, though, there remains an awful decadence in connecting empty guts to spirituality. There is nothing spiritual about famine.

We all live with this dreadful duality. We can witness the passive gaze of those who are too broken to ask for help and on the next page we can read advice from that paragon of health, Courtney Love. Love was a big fan of colonics until 2007. Then she stopped, following a fraught car journey in which she had "to use the lavatory after one treatment went 'horribly wrong'". Lovely.

Now people fly all the way to Thailand to stick tubes up themselves and squat over holes. Last year I found myself deep in the West Country being asked to do much the same. I had agreed to go to what I believed was a spa with a friend who was grieving. We both thought some sort of R&R would do her good. To be frank, I didn't think too much about it, imagining a week of eating salad in the countryside. When I arrived, I realised we were at a hippy bootcamp. The next shock was to find not only was there no food but we were expected to perform DIY colonic irrigation twice a day! All we had was watered-down juice and psyllium husks mixed with water, which as far as I could tell was indistinguishable from wallpaper paste. This was all combined with endless group therapy, some vaguely Buddhist meditation and lectures on nutrition from people who, despite no medical training, knew better than the entire medical establishment.

Right from the start I thought the colonic business was deeply dangerous because it involved balancing on a board over a loo with a bucket of water. I wasn't so much worried about perforating my bowel (one of the more unpleasant side-effects of this practice), but falling off this narrow board, breaking my back and having the bucket fall on my head, thus leaving me unconscious and in the care of these new-age nutters. For ever.

It is fair to say I lost my mind. My resistance, of course, was met with condescension. I was angry because the toxins were coming out. My feelings of hunger weren't actual feelings of hunger – I was getting in touch with my inner child. If this were true, I would have eaten it. My questioning was part of my over-intellectualised armour, rather than the result of my reading about the philosophy of what was going on while I was unable to sleep. Electrical devices were frowned upon, but of course I had smuggled in an iPad. Thank Christ.

The group of people I was with were mostly lovely. They felt what they were doing was providing all sorts of benefits. It's true that if you don't eat anything and give yourself constant enemas, weight loss will occur (though not last). Yet as any doctor will tell you, we have organs to detox us – kidneys and livers – and if they don't work, we are in big trouble. Colonic irrigation depends on finding something else to remove. So we had lectures about "mucoid plaque" – undigested stuff that stays in your guts for decades, producing all kinds of bad symptoms.

This confused philosophy is not new. For the Egyptians, then the Greeks and then extending into the medieval period, the idea of "auto-intoxication" was prevalent – decomposing food inside the intestines causing illness. But those who actually cut bodies open – surgeons or those conducting autopsies – find no evidence of the intestines full of strange black stuff that the colonic cult boasts of in its group sessions. I sat in wonder as middle-class women, one after another, explored and examined in detail, not to put too fine a point on it, their own shit.

The "evidence" for this, as with much alternative medicine working, then, is anecdotal and exists only in the imagination – but that imagination is vivid enough for a thriving business. All the fine doctors and sceptics who rail against such nuttiness never take into account the psychological reasons that people seek out these forms of help. Why do we want to feel cleansed, for instance? Debunkers of alternative therapies rarely treat the symptoms – they just dismiss the silly practices.

More and more I see closed arguments between new-agers immune to evidence (with their prana and vital energies and chi, which in the end, come mighty close to God) and fundamentalist rationalists who will not budge an inch.

Surely good doctors always have worked "holistically". The fears of Big Pharma are now fuelled, weirdly, by the rightwing as well as the flat-Earthers. But who cannot worry about the drugging of the underclass with antidepressants and Ritalin? Science provides the best answer until a new one comes along, and until that bizarre week of fasting, I saw myself as a sceptic. Yet, strangely the sceptics' sneers are now as off-putting to me as jangling dreamcatchers.

Many of the sceptic movement's proponents do it no favours. Science and evidence are their gods, but they lack the emotional intelligence to win anyone over. I objected to taxpayers funding the Pope's visit as much as the next atheist, but the spectacle of "intellectual" men sneering at devout Catholic women was horrible. Fundamentalist atheists and sceptics are not interested in changing minds, but simply shoring up each other's cleverness.

The best advocates of science, such as Brian Cox, show us that transcendence already exists in the universe. The best humanists acknowledge that rituals around birth, death, cleansing and fasting are part of our narrative. I want a scepticism that queries rather than condemns. So I am perfectly happy to say colonic irrigation is crap, but not happy to insult everyone who veers away from the mainstream. Snake oil comes in vast containers these days, from the top down. Deep down, the problem is not in our bottoms, but in our minds.