Can stevia nix obesity?

It's natural, calorie-free and as sweet as sugar – no wonder the food industry is excited. But does stevia pass the taste test? Kristen Herhold reports

Sweet and low: the stevia plant, which grows in South America (Alamy)

It looks like sugar, acts like sugar and tastes a lot like sugar, too. But stevia is a sweetener with no calories, which is having a major impact on the food industry and some say could help to fight obesity and diabetes. What's making the food industry excited is that, unlike other sugar substitutes, stevia is an entirely natural product.

Native to South America, it can be traced back thousands of years, to when the people of Paraguay and Brazil used it to sweeten foods. Sold commercially in Japan for more than 40 years, it's only in recent years that it's been available in the UK and the USA. But it's rapidly catching on, with an increase in US sales of 400 per cent between 2008 and 2012, as consumers are drawn to its sugar-like qualities, but with zero calories and zero guilt.

The sugar company Silver Spoon has been quick to get a foothold in the market. Its Truvia product, a sugar substitute made with stevia, has become the second-best selling sugar substitute in the US since its launch in 2008. It has been on the markets in the UK and Europe since 2011, when stevia was approved for consumption by the European Food Safety Authority.

"In each country that we've launched in, the sugar-substitute category has grown following the launch of Truvia," says Mark Brooks, global business director for Truvia consumer products. "You get the great taste, you get the functionality, and you just leave behind the calories for added sugar. So consumers have found a product that resonates with them." Too good to be true? Maybe. The flavour of Stevia takes some getting used to.

With complaints of a liquorice-like aftertaste, not all consumers have been happy with products enhanced with the sweetener. The dairy company Danone, for example, eventually decided to change the recipe for its stevia-sweetened yoghurts because of poor consumer feedback due to its aftertaste.

To combat the aftertaste, some companies are still including sugar in their stevia-sweetened products, finding that the combination can be a little more successful.

"We just launched in the UK a baking-blend product that gives you 75 per cent less calories but is 50 per cent sugar because sugar does something and it'll help your product bake," Brooks says. "We've spent over 80,000 hours doing work with Truvia. We focus on the most important thing, which is taste, because calorie-free is important, coming from a stevia plant is important, all those things have to be true, but ultimately you use Truvia to enhance something else. And so it better taste good."

The marketing director of Silver Spoon, Tony Lucas, however says that aside from a minimal amount of complaints the vast majority of consumers enjoy Truvia. "As with any new food you launch, you get some people who really like the taste of it and some people who aren't so keen on the taste," he said. "As we expected, we had one or two comments from people who didn't like the taste, but the vast majority of people think it's fantastic."

After trying stevia myself as a sweetener in a drink, I did not notice a bad or liquorice-like aftertaste. I was, however, surprised by how chemical it tasted, which is surprising considering it is the only natural sugar substitute.

Products made successfully with stevia may also have potential for helping to combat the growing problem of obesity. According to the National Health Service's 2013 Statistics on Obesity, Physical Activity and Diet, 65 per cent of men and 58 per cent of women are overweight or obese in England, and the numbers continue torise. As the population increases in size, more and more people are looking for ways to shrink down – and cutting out sugar could certainly help. There are, of course, other zero-calorie sugar substitutes, but stevia is the only one of natural origin and that is something consumers find appealing.

"Stevia can help people enjoy natural-origin sweetness while reducing calories as part of a healthful, balanced diet," says Dr Margaret Ashwell, a member of the Scientific Advisory Board of the Global Stevia Institute, an information service provided by the main suppliers of stevia. "There are enormous opportunities for industry to meet national and international pledges to reduce sugar in products to help the obesity crisis." Stevia also allows consumers to satiate their sugar cravings guilt-free. Food scientist Professor Jeya Henry, professor of nutrition and director of the Functional Food Centre at Oxford Brookes University, agrees it has a lot of potential for sating our collective sweet tooth.

"It's much easier for people who don't have diabetes to tell people not to eat sugar, but one of the driving forces of our life is the pleasure of food," he says. "So if you can apply the pleasure of food to stevia, why not? At the end of the day, we are creatures of food desire." But Professor Henry is cautious about hailing it as a cure-all. "Stevia can make some contribution, but it is not a panacea for obesity," he adds.

In the UK, stevia can be found in the reduced-calorie versions of Sprite, Nestea, Tropicana Orange Juice and various yoghurts, sometimes alongside sugar and sometimes replacing it.

In 2010, a panel of 21 European food safety scientific experts read reports on stevia, including its toxicity and its possible effects on genes and the reproductive system and deemed it to be safe. Though the long-term effects of stevia have yet to be extensively analysed, Brooks said consumers should not be worried. "We invested in years of rigorous safety studies," he said. "We would not bring a product to market unless we were confident we could recommend it to our consumers and customers."

Professor Henry says he believes consumers have no need to fear any negative health effects from stevia, with its long history. "It has been used for more than 3,000 years by the South Americans," he says. "Everything we eat and do has a potential risk. I would certainly think that stevia is probably a pretty good bet in our contemporary society where people are always saying Mother Nature is better than anything synthetic."

Dr Robert Lustig, author of Fat Chance: The Bitter Truth About Sugar, however, believes that the lack of research on the long-term effects of stevia is alarming. He says because the body expects real sugar, when it is not given sugar weight-loss goals could backfire.

"We don't have the information yet," he says. "And unfortunately we're not going to be getting that information any time soon. So I have to remain agnostic on that point because the science, the data just isn't there."

Researchers at Purdue University in Indiana found that in addition to being lower in calories than sugar, stevia is also better for your teeth. Unlike sugar, a main contributor to dental caries and tooth decay, stevia does not cause tooth decay and can even fight it by preventing plaque from forming on teeth, the study says.

Though it is produced much like sugar, stevia is still much more expensive due in part to the fact that the demand for stevia is still considerably lower than that of sugar. In fact, stevia can cost 10 times as much as sugar.

Despite its expense, it doesn't look as if stevia's popularity is going anywhere any time soon, and more and more people are likely to continue to enjoy this zero-calorie natural product. "The market will continue to grow," Lucas predicts.

"Each month, we're selling more. People like that it's natural and that it's zero calories, but they also like that it is a granular texture just like sugar. That's what makes it unique."