The large intestine is closer to the butt hole, and part of its job is to absorb water from poo to keep us hydrated. The small intestine, which is further up, is where nutrients and also potential toxins get absorbed and sent to the blood.
Here's the kicker: a colonic only washes out the large intestine and it "goes nowhere near the small intestine," says Graham. That means any "toxins" in the gut would have been absorbed further up.
"If your bowels work normally there is zero science - zero science - in using colonic lavage," says Graham. "It's a load of rubbish. It's as simple as that."
Two academics papers that trawled through the research on colonics found there is no good science to support using them unless people have digestive issues.
Graham says that it can feel good to get a colonic. (I asked him if it was "like doing a big crap?" And he said "Yeah, that's all, nothing more.") But, he says, there are risks involved.
It's hard to know how common these are, but people can end up with bouts of vomiting, diarrhoea, kidney failure or perforated intestines.
Perhaps the solution to a good detox can be found elsewhere? Juice cleanses are big business right now. It's estimated that cold-pressed juice companies, raked in almost half a billion dollars last year.
With their claims that drinking a diet of juice can "release the toxins built up inside", I thought I'd give it a go. I committed to 24 hours of eating no food whatsoever - only juice, and by the end, I was promised to feel "an energising, clarifying, and brightening effect".
Juice cleanses are a bit vague on the details of how juicing will achieve that. And, after much searching at Science Vs, we couldn't find any evidence to suggest that putting food in a juicer could help you get rid of toxins. But we did notice that a lot of these juicing detoxes, promise that juicing can kickstart weight loss. Can it?
Putting something in a juicer doesn't necessarily make it healthy. Juices can have a lot of calories and a lot of sugar. It all depends on their ingredients. One "green juice" that I was drinking had almost half the sugar found in a can of Coke. It's not added sugar, it's naturally found in fruit, but it's still energy.
All this sugar is part of the reason why two researchers recently wrote in the Lancet that pure unsweetened juice should be characterised as "sugary drinks", just like sodas.
Juices also often lack fibre, says Professor Stella Volpe at Drexel University in Philadelphia.
Our bodies don't digest fibre, instead it creates this "bulk" in our intestines, that might trigger feelings of us being full. Studies going as far back as the 1970s found people get less hungry after eating whole fruits compared to juice.
That means, if people are eating a regular diet and drinking lots of juice, they might be taking in more calories than usual. If they are just drinking juice and otherwise fasting, then during the "juice detox" they're probably consuming less calories than normal, but other symptoms might emerge.
For me? After a day of juicing I felt tired, had a headache and couldn't concentrate. The next morning, suffice to say, I didn't feel brighter or more energised. Given the lack of science behind this juicing nonsense, I shouldn't have been too surprised.
Still, for those who are desperate to detox, science has some great news for you. We are already detoxing on a daily basis. Our kidneys are efficiently sifting through blood for potential toxins to pee out, and part of the liver's job is to take toxic substances and convert them into something harmless. No expensive juicing or colonics required.
