Stop the juices

EAT, DON'T DRINK

I  wake at 3am, head pounding, dripping in sweat, shaking and itching all over. I know I’m going to be sick, but when I try to walk to the bathroom, I feel faint and lights start flashing in front of my eyes. I crawl instead, vomit and crawl back to bed. My mind is muddled, but one thought makes its way through the fug: am I dying?

No, I’m 48 hours into a juice fast. On each of the past two days, I’ve drunk four small vegetable and fruit juices and eaten precisely nothing. This equates to a daily calorie content of 400, less than a quarter of my usual intake.

Downstairs, the people running the retreat I’m attending take one look at my grey, frightened face and do a pinprick blood-sugar test on my finger. It reads 3.6 millimoles per litre, which is low; the normal range is between four and eight. I’m experiencing – as a variety of doctors, dietitians and nutritionists later tell me – hypoglycaemia.

“A blood-sugar reading under four means you’re having a hypo,” the NHS dietitian Nicky Vernede, who works for Oxford Health Foundation Trust, says. “That should only really happen when you have diabetes. That’s low for a normal, healthy person. Two consecutive days of 400 calories is extreme fasting – your body would have been in complete shock.”

Back at the retreat, I return to my room, climb into bed and am given some apple juice and – rejoice! – solids: glucose tablets and crackers with hummus. I take a few cautious sips and nibbles and instantly feel better. My eyelids become heavy and when I awake several hours later, I am human again.

The juice fast may not have agreed with me, but there are a lot of evangelists out there. Of the 15 people on my retreat, I was the only one to react in that way. Many were regulars and swore by the regime, returning home pounds lighter, energised, deeply rested and with glowing skin and sparkling eyes.

Food is a status symbol like never before, and there’s no middle ground when it comes to the obsession with what we put into our mouths. It’s either all (I give you the fetishisation of home baking and the ubiquitous cupcake) or nothing (the rise of fast-based diets). The claims made by juicing proponents are as big as the money involved: these elixirs can purportedly do anything from aiding weight loss and helping skin conditions to curing arthritis and cancer.

The medical community, however, is less enthusiastic. “So many people seem to find some benefit from it and there are so many books about it, you think maybe there is something in it. But everything I know about it suggests it’s not a good idea. I’ve heard the anecdotes, but show me some bloody evidence that it works,” Michael Mosley, the doctor and television documentary maker, says.

But hold on, this is the same Michael Mosley who made the 2012 Horizon documentary that offered a compelling, science-based argument for intermittent fasting, before going on to write the bestseller The Fast Diet, a fasting-based eating plan working on the 5:2 model. This involves eating normally five days per week and fasting (well, consuming 500-600 calories) on the other two.

“I’d never recommend juice on a fasting day,” he says. “It’s about solid food.” The problem with juice fasts, Michael says, is the lack of protein. “You need protein to fill you up. Unless you have adequate amounts of it, within 24 hours your body starts to cannibalise itself and get protein from your muscles.

A juice diet is zero protein, so you will lose a small amount of fat and a large amount of muscle. And if you lose muscle your metabolic rate will slow down.” Which, if you’re trying to lose weight, is hardly welcome news.

Science behind sugar

Then there’s the lack of fibre in juice. Dr Robert Lustig is the author of Fat Chance: The Hidden Truth About Sugar, Obesity and Disease and has spent 16 years treating childhood obesity. “Eat your fruit and veg, don’t drink it,” he says. “There are two types of fibre, soluble and insoluble.

When you juice, the soluble fibre is still there, but the insoluble fibre is sheared to smithereens by the blades. Consumed together these two fibres form a gel in your intestine, which limits the rate of absorption of sugar. That’s a good thing – it means all the sugar isn’t delivered to the liver at once, because when that happens the liver is going to turn it into fat. But when you juice, this gel can’t be formed.” The result is a spike in blood-sugar levels. “If you look at the blood-sugar rise after eating an apple compared with drinking apple juice, the latter creates a much higher rise,” Dr Robert says.

Fructose – the type of sugar found in fruit and many processed foods – is the big enemy here, according to Dr Robert’s research. Glucose is removed from the bloodstream by insulin, but there’s no equivalent hormone for fructose. That job falls solely to the liver, which, if overwhelmed by fructose (say, if you’re drinking gallons of juice), can convert it to liver fat. This increases the likelihood of insulin resistance, furred arteries and heart disease.

The other problem with fructose is that it suppresses leptin, the hormone that tells you when you are full, so you don’t know when to stop. Dr Robert acknowledges there is a big difference between juicing vegetables (which are low in sugar) and fruit, but is unequivocal in his belief that juicing fruit is akin to drinking cola.

Public Health England’s (PHE) chief nutritionist, Dr Alison Tedstone, also points out the dangers of dental decay from too much juice, as the acid strips tooth enamel – something I’ve heard anecdotally: a couple of friends gave up juicing because their teeth hurt. “Detoxing is a nonsense term; it’s not a physiological thing,” says obesity researcher Zoë Harcombe. “There’s a lot of money in the juicing industry – all those retreats and fancy machines. But people are deluded.”

As for me, the probability of another juice cleanse hovers around zero. I might buy a green juice when once I’d have grabbed a Diet Coke, and I do occasionally knock up an apple, kale and cucumber concoction to help face a hangover, since the idea of eating greens with a bacon sandwich seems ridiculous. But whether this makes me healthy or delusional, I’m still not entirely sure.