Freshly made fruit juice is one of life’s great pleasures. From plain and simple orange or apple to complex concoctions containing vegetables, herbs or even spices, it’s never been more popular.

Sales of juicers and blenders have soared. No wonder advocates claim drinking juice and smoothies is incredibly healthy — an easy way of getting huge amounts of micronutrients, including vitamins, minerals and cancer-preventing antioxidants into our bodies.

Jason Vale, the self-styled ‘Juice Master’, even credits the craze with ridding him of psoriasis, eczema and hay fever. So what could be better for a nation in the grip of an ever spiralling fast-food addiction and obesity epidemic than a new-found love of making juices? Well, unfortunately, they aren’t always as healthy as you’d think.

Experts are so concerned about the dangers — some labelling it ‘as bad as Coca-Cola’ in terms of sugar content — that there are calls to ban juice from being one of our ‘five a day’ (drinking 150ml of unsweetened juice qualifies as one of your daily total).

Our addiction to juice is being held partly responsible for weight gain, the spread of type 2 diabetes, and even dental problems.

What’s more, health advisers argue that so much damage is done to the goodness in fruit when you extract the juice or turn it into a smoothie in a blender, it’s far better to just eat the original apple, banana or orange.

"The mechanism of consuming a whole piece of fruit is undoubtedly better for you on every level; weight loss, fibre absorption and nutrients,” says nutritionist Jackie Lynch.

There’s no question that fruit and vegetables are good for us — they help protect against strokes, high blood pressure, heart disease and even some cancers as well as providing important nutrients, including zinc, for the immune system, and folic acid for making red blood cells.

The problem is, juicers reduce many of these health benefits. They extract every drop of liquid from, say, an orange or apple and leaving much of the pith, peel, core and pips behind. But it’s these parts of the fruit that contain the fibre which is so vital for our digestive systems.

Fibre helps promote beneficial bacteria in the gut — vital for preventing constipation and reducing the risk of bowel cancer. It’s also thought to play a major part in keeping our immune systems healthy as well as preventing conditions like inflammatory bowel disease, and autoimmune disorders such as rheumatoid arthritis.

Fibre also helps you to feel fuller for longer   and aids the absorption of nutrients, especially minerals such as calcium, into the body. Take fibre away and you remove these benefits.

There’s also the question of the acid content of fruit giving you an upset stomach. Fruits such as oranges and lemons contain high amounts of citric acid, which may irritate the sensitive lining of the stomach, leading to pain, sickness and upset tummies.

You may think that making your juice in a blender would be better because, unlike juicers, they crush everything, including the fibre, and turn it into a drink.

But it’s still not as good as simply eating the whole fruit, says nutritionist Scott Laidler.

"Even if you use the entire fruit, the blades in your juicer will break down some of the cellulose [part of fibre], affecting fibre levels. You are unlikely to get the same fibre as you would from just eating it,” Laidler says.

Another problem caused by juicing is that nutrients in a piece of fruit start to be lost the moment you cut into it.

Breaking nutrients down

Nutritionist Monica Reinagel says: "The antioxidants and other phytonutrients start to break down almost immediately they are exposed to light and air, as part of the oxidation process, where, for example, apples turn brown once sliced into.”

This means that crushing your fruit in a juicer could lead to losing the benefits of antioxidants such as the polyphenols found in berries, which keep arteries healthy and aid mental health.

Vital nutrients continue to diminish if you store your juice or smoothie in the fridge to drink later. One study reported that up to a quarter of vitamin C content was lost in cut pieces of kiwi, pineapple, mango, strawberry, watermelon and cantaloupe over a period of six days when the fruits were stored in the fridge.

But these aren’t the only problems. Anyone who’s ever had a conventional juicer will know just how tricky those cutting blades can be to clean. Yet fail to do so properly and they become a breeding ground for harmful bacteria.

In 2011, a study looked at the effects of serving drinks from dirty juicers in cafes and found that microbes, including salmonella and E.coli, could thrive if juicers weren’t washed properly.

The Mayo Clinic, a non-profit-making research group in the US, says it’s essential to drink fresh juices soon after they’re made because of their increased vulnerability to bacteria (or, if already contaminated, to bacteria multiplying) when stored, especially if they are not kept cold.

Then there’s sugar, the crystal meth of the masses. We all know that fruit contains a lot of sugar, but while few of us would eat four oranges in one go, that’s how many one standard glass of 250ml juice could contain. That’s a staggering 22g of sugar and nearly 120 calories.

Apples contain even more sugar; 26g in a single 250ml glass. And while blenders like the Nutribullet, which can also be used to make healthier vegetable smoothies, use less fruit than conventional juicers to produce a glassful, they still create problems.

"By crushing your apple rather than simply biting into it, you are effectively making a sugary juice as you release the fructose, a type of sugar which is naturally found in fruit,’ says Laidler.

Usually fructose is contained within the cells of the apple and broken down slowly as part of the digestive process. While you aren’t creating more sugar by crushing the apple, you are making it much easier for your body to absorb.

This means the body has to release the hormone insulin to regulate the increased sugar levels in your body, creating an ‘insulin spike’, which means you need to burn off the sugar by exercising or it will be stored in the body as fat.

And once that sugar wears off, you’ll be hungry again much sooner than if you’d eaten the same amount of calories in protein or fat.

In fact, any time you drink fruit juice rather than eat fruit, you are setting yourself up for a so-called sugar crash, where, just a few hours after eating, you crave something sweet.

Cue a raid on the fridge; and a ruined diet.

If you keep on raising blood sugar like this over a long period of time you may become insulin resistant, which is where the body cells stop responding to the hormone. This is a pre-diabetic state that increases your risk of developing type 2 diabetes.

"When you eat fruit and vegetables, saliva starts to break them down and they pass through the digestive process,” says Lynch. "If you simply decant five pieces into your stomach in liquid form, you are by-passing this necessary and complex process.

"First, you won’t activate the satiety mechanism, which is released by the action of enzymes produced by saliva as you chew the food and helps the body recognise that it’s full, so you may end up eating more.

"Second, you are actually burning fewer calories because your body isn’t using any energy to break down the food. This means that calories from the natural sugars in the juice aren’t offset by those usually used in digestion. Chewing, absorbing and processing food burns up to 200 calories a day in what is called the thermic effect. By consuming juice, you’re basically losing the opportunity to burn up to 200 calories.”

Even dentists are worried about this latest health trend. They’re seeing more cases of acid erosion — the softening and loss of tooth enamel caused by the acid in soft drinks — than ever before. As enamel is the material that protects teeth, softening it can lead to decay, fillings and crumbling molars.

"Juice from fruits has a high acid content and can damage the enamel of your teeth in exactly the same way that a fizzy drink does,’ says Dr Uchenna Okoye, of London Smiling dental practice.

"If you’re going to drink juices, always use a straw. Never brush your teeth straight after drinking, as the teeth are weakened by the exposure to acid.”

This article was first published in The Daily Mail, UK