In Australia, steviol glycosides, extracted from the Stevia rebaudiana plant, are approved for use by Food Standards Australia New Zealand (FSANZ) as an intense sweetener under the food additive number 960.
Under the FSANZ code, there are no guidelines concerning use of the word “natural” for marketing food additives. But Dr Alan Barclay, spokesperson for the Dietitians Association of Australia, says the idea that stevia extracts are completely natural is misleading. “People are not buying pure stevia leaves straight off the plant – they are buying a highly purified extract that is usually blended with sugar alcohols and oligosaccharides such as dextrins.”
There is currently debate in the EU about labelling steviol glycosides as natural. Some health food stores in the UK and France refuse to stock stevia-based products, and marketers are considering alternative claims such as “stevia from a natural source”.
Steviol glycosides do not taste like white sugar and have a bitter aftertaste that falls somewhere between liquorice and treacle. As a result, stevia cannot supply more than 50% of the sweetness in a manufactured food or drink and still be palatable.
For this reason, steviol glycosides are often mixed with other substances to provide bulk, or improve taste and texture. This means the low-kilojoule and low-GI benefits of stevia can end up being compromised by other added ingredients, including sugar, sugar alcohols, maltodextrin, unspecified “flavourings”, lactose, croscarmellose sodium, sorbic acid, cellulose powder and silicone dioxide.
As an example, Pepsi Next states it is “sweetened naturally with stevia”. However, a quick look at the ingredients list reveals that after carbonated water, sugar is the second-highest ingredient. One can contains 27.8g total sugars (more than five teaspoons) and 445kJ. It does have 30% less sugar than regular Pepsi, but being “naturally sweetened” doesn't make it a healthy drink.
Compared with sweetener products from brands such as Equal and Hermesetas, which have flavours and other additives, Natvia has only two ingredients, steviol glycosides and erythritol. The marketing blurb says its stevia is “100% natural” and mixed with a “naturally occurring nectar known as erythritol”.
Erythritol is a sugar alcohol – a type of carbohydrate found in fruits and vegetables – and Barclay says it’s going a bit far calling it completely natural. “Although erythritol does occur naturally, to obtain the amounts required, it is actually produced by the food industry in manufacturing plants.”
Natural or not, the good news is that there is currently no evidence to suggest stevia is unsafe. The World Health Organization has determined a recommended daily upper limit of 4mg per kilogram of body weight per day – an amount most people would be hard pressed to consume.
Stevia and obesity
Stevia has been hailed as “a key ingredient in the fight against obesity”, but as Di Harvey from Diabetes Victoria points out, kilojoule-free sweeteners have been around for a long time yet have had little impact on obesity. She adds that low-kilojoule sweeteners also tend to be added to heavily processed foods that are high in kilojoules, refined carbohydrates and sodium, which should be minimised anyway.
While it’s true that sugar is high in kilojoules and devoid of nutrients, evidence suggests our overall dietary patterns are more important in terms of weight loss than simply the amount of sugar we consume. Ultimately, Barclay says the evidence around the weight-loss advantages of low-kilojoule sweeteners isn’t compelling.
A systematic review in 2012 determined there is insufficient evidence that NNS used in drinks and foods reduce the consumption of added sugars and carbohydrate intakes, or that they benefit appetite, energy balance, body weight or cardiovascular disease risk factors.
“Rather than fixating on and excluding an individual food, such as sugar, people should focus on eating less of all foods to reduce overall kilojoule intake and eat more whole foods in their natural form,” says Barclay.