Coca-Cola Life will contain a natural sweetener - but how do sugar substitutes measure up?

Quest to find a sugar alternative is now a multibillion-pound industry

Sweet sensation: the body produces physiological changes as soon as sweet things are in the mouth (Getty Images)

Drinkers of Coke generally fall into one of two camps: diet (zero calories, no sugar) or "full fat" (the original, sugary version). From September, though, a compromise option will be added, as the drinks giant launches Coca-Cola Life, which contains 89 calories.

A 330ml green can of this new drink contains 22.1 grams of sugar, compared to 35g in regular Coke. But to keep it just as sweet as the original, its maker has added stevia, a calorie-free extract of the leafy South American stevia plant that many see as the next big thing in low-calorie sweeteners. It represents a big step forward for the sugar-replacement industry, which is already growing fat on our growing demonisation of sugar.

Studies have linked excess sugar consumption not only to obesity and diabetes but also to heart disease and depression. A slew of new books advocate the low-sugar lifestyle, from model Daisy Lowe's Sweetness & Light to journalist Nicole Mowbray's compelling account of quitting sugar, Sweet Nothing.

The World Health Organisation says that sugar should comprise just 5 per cent of our calories. That's roughly 25g per day, or six teaspoons (less than in one can of original Coke). According to the National Diet And Nutrition Survey, non-milk sugars currently make up more than 11 per cent of Brits' daily calories, with teenagers getting more than 15 per cent of their energy from it.

For food lovers, this presents a conundrum. Because sugar may be bad for us – but it's everywhere. Not just in packaged food; not just in cakes and puddings. It's in plenty of "savoury" dishes too: Japanese sushi rice and Sicilian caponata, Middle-Eastern stews and Malaysian curries. No wonder the quest to find an alternative – a product mimicking sugar's delicious taste, without the ruinous side effects – has become a multibillion-pound industry.

The sugar-replacement business – which began in 1879, when researchers at Johns Hopkins University discovered a calorie-free coal derivative named saccharin – is worth a reported £6.3bn. It's predicted to exceed £8bn by 2018. Supermarket shelves heave with the results: agave nectar, manuka honey, Truvia, Splenda and Canderel. But what are these products – and can they offer an alternative to those of us who don't feel able to forgo sugar for ever?

Broadly speaking, sugar substitutes fall into three categories. There are artificial sweeteners – chemical additives, such as aspartame (in Canderel) and sucralose (in Splenda). Then there are the natural alternatives to table sugar: among others, honey, maple syrup and agave nectar, extracted from Mexico's cactus-like agave plant. These all contain sugar – but in a supposedly "healthier" form than table sugar (more on this later). The third group consists of naturally sweet substances that don't contain any sugar – or calories.

The first – the artificial sweeteners – taste OK in diet soda but you can't imagine pastry chefs adding them to their profiteroles. They may also share sugar's ill effects. In studies, rats fed on artificially sweetened foods ate more overall than those fed on sugar.

Going green: The new Coca Cola Life sweetened with stevia (COCA COLA)

"The body produces physiological changes as soon as sweet things are in the mouth," explains Susan Swithers, professor of behavioural neuroscience at Purdue University in the US. "These contribute to regulating blood sugar and producing feelings of fullness. When sweeteners are used, the calories don't arrive. Over time, normal responses to sweet tastes get smaller, and we may eat more."

There's also something inherently unappealing about cooking with a lab-concocted chemical. Far more tempting are the agaves, honeys and maple syrups. They come with celebrity supporters, including Gwyneth Paltrow and Lowe, and taste delightful. For manufacturers, business is booming. Between 2008 and 2013, the British maple-syrup market grew from £8m to £12m; sales of honey increased 8 per cent between 2010 and 2012 to reach £107m.

Yet despite their wholesome reputation, they're not that different from sugar. They have roughly the same number of calories. But whereas table sugar is sucrose, a compound of half glucose, half fructose, these alternatives tend to be high in fructose. Some agave nectars are 92 per cent fructose. Unlike glucose, which is absorbed into the bloodstream as it passes through the small intestine, fructose isn't metabolised until it reaches the liver. As such, it doesn't produce the same immediate blood-sugar spike linked to cravings for more sugar and falls lower on the glycemic index than sucrose and glucose.

But fructose has its own problems. Michael Goran, professor of preventive medicine at the University of Southern California, says: "Fructose is converted to fat, which either stays in the liver or gets exported into the circulation. Build-up of fat in the liver causes liver problems and insulin resistance." A claim often made of these products is that they're better for us because they are less refined than table sugar. However, that doesn't negate their ill effects. As nutritional expert Ian Marber puts it: "We seem to be elevating many products to being great, when in fact they are pretty much the same." Marion Nestle, professor of nutrition at New York University agrees. "The bottom line is that diets are healthier when they contain less sugars of any type."

Which brings us to the third group: naturally sugar-free sweeteners. There are around 100 naturally occurring chemicals that taste sweet. They can be found in animals' tears and spit, egg whites and plants. To be used as a commercial sweetener, however, they must meet all sorts of requirements – withstanding temperature changes, sweetening in solution, storing well.

Get it wrong, and the effects are disastrous. In 2012, scientists tried using an amino acid drawn from South Africa's molomo monate plant in soft drinks. The results tasted great but, when exposed to sunlight, turned dark yellow and smelled of faeces.

The best natural prospect so far is stevia, the sweetener found in the new Coca-Cola Life. Used in Japan and South America for decades, it arrived in the UK in 2011. Between 2008 and 2012 there was a 400 per cent global increase in stevia product launches, according to Mintel.

Mainly sold in the UK as Truvia, it contains neither sugar nor carbohydrate, and doesn't raise blood sugar. More research is needed – but in 2010 it was deemed safe by a panel of 21 European food safety experts.

Still, stevia's not perfect. Some complain of a bitter aftertaste. In moderation, it's subtle; in concentration it would be off-putting. You can bake with it, but have to add extra liquid to create bulk – stevia is sweeter than sugar so recipes call for a smaller volume. However, food and drink manufacturers have had some success when using it alongside sugar to reduce the calorie count of their products.

For now, then, the hunt goes on. In the meantime, gourmands have two options. They can shrug off the health consequences and continue to enjoy the same foods that they have always eaten. Or they can cut back on sugar and its substitutes, and train their palates to enjoy less sweet food. "There's not really a cheat," says Mowbray. "The only way is to change your perception of sweetness and treat yourself in other ways." This might be easier than it sounds. While profiteroles are off the menu, cooks are finding creative ways to cut down on sugar.

Mowbray's book includes recipes for porridge and "energy balls" made from sweet potato and almond butter, as well as brownies and chocolate mousse made with avocado and raw cocoa. "Rather than replacing sugar, use the change to try new flavour combinations," says chef Mike Denman, of London restaurant Plum + Spilt Milk. "Cinnamon can be a really good addition," says Mowbray. "People add it to coffee or porridge."

As for the perfect sugar substitute? One thing's for certain. Whoever does discover it will be left feeling very sweet indeed.

HOW TO CUT BACK ON SUGAR – AND STILL ENJOY YOUR FOOD

Swap low-fat for full-fat

"Low-fat yoghurts often have more sugar added to them than their full-fat counterparts," explains the author Nicole Mowbray.

Experiment with spice

Martyn Moody, of London's Blueprint Café, recommends cooking with cinnamon and cloves: "You'll find that you don't need as much sugar because the spices provide depth of flavour."

Try new things

"There are plenty of delicious dishes that don't rely on sugar," says Plum + Spilt Milk chef Mike Denman. "Rather than trying to replicate those that do, try new recipes or use ingredients that are naturally sweet, such as onions."

Treat yourself

The occasional sweet treat isn't going to kill you, says Mowbray: "If you cut back on sugar on a day-to-day basis, then it doesn't matter if you have that one slice of cake. If there's something I really want, I will have it."