The principle problem facing the treatment of stevia from a regulatory position is a general lack of study. While the sweetener has been generally accepted as a harmless sugar substitute, there is a paucity of long-term, scientific study into the potential negative effects of stevia and sweeteners like it. While several concerns have been addressed through study, there are still questions that need answering and the perhaps too easy acceptance of stevia seems based, at least in part, on less-than-concrete evidence (the long history of use in Japan, for example, has helped with its positive image).

Meghan Azad, assistant professor of pediatrics and child health at the University of Manitoba, told the New York Times, “Overall, for nonnutritive sweeteners, we lack evidence, but that’s especially true for stevia.”

Azad was the lead author of a review of long-term use of nonnutritive sweeteners, which concluded that, aside from potentially not aiding with weight loss, they were associated (in some studies) with increased incidence of obesity, diabetes and heart disease. However, neither Azad nor her co-authors found any long-term studies of stevia specifically that could be added to the review. While it is possible that their broader conclusions of concern could be applied to stevia, without specific evidence, and given the general lack of hard evidence currently present, it is hard to make any prescriptive decision about the treatment of stevia.

Azad continued however, “Just blindly assuming that these are a healthy alternative to sugar is probably not a wise move without the evidence to back it up.”

One of the main attractions of stevia, aside from its more natural origins, is the lack of calories contained in stevia sweeteners. For those looking to control their diets by cutting down sugar and other calorific foodstuffs, the promise of a sweetener with no calories seems like it could be too good to be true. By cutting down on the calories, but still providing the sweetness, stevia could allow consumers to satisfy any cravings they have without putting their health at risk of any obesity concerns arising from high calorie intake.

Nutritionist Keri Gans, a spokesperson for the American Dietetic Association, told NBC News, “Given our nation’s problem with obesity, stevia and other artificial sweeteners have a place for people who consume more calories than they should from sweets. But artificial sweeteners should not take over your diet because that means you’re eating way too many processed foods.”

Moreover, the calorie-cutting effects of stevia may not be as beneficial as advertised. Although yet to be conclusively studied on a large scale and over a long period of time, it has been suggested by researchers that the taste of sweetness without any calorific reward may in fact lead to altered regulation and consumption of sugar in other foods. A small study published in the International Journal of Obesity in December 2016 for example, found that participants who received a stevia sweetened drink in the morning rather than one sweetened with sugar were likely to compensate by eating more at lunch.

Similarly, in February 2008 it was reported by scientists at Purdue University that rats fed food with the artificial sweetener saccharin went on to consume more calories and put on more weight than rats fed food sweetened with glucose. While not a direct comparison, the study lends weight to a broader belief that artificial sweeteners may disrupt calorie regulation. Rather than being the miracle supplement suggested by the lack of calories, it may in fact be that the lack thereof lends stevia and sweeteners like it to pose an equal or greater calorific risk to sugar.

In spite of these concerns, stevia’s success shows no sign of slowing in the near future. According to FoodDive, stevia-included product introductions increased by 25% in 2017 and US stevia sales are expected to grow by 7% per year until 2022. In terms of growth and market value alone, stevia is making a significant impact, with Statista reporting that the global market value grew from $336m in 2014 to $578m in 2017. Additionally, according to research by the International Stevia Council, stevia has been found to be the most favourably viewed of all low-and-no calorie sweeteners.

According to Bloomberg, stevia is doing any better and has become a $4bn industry in the last decade (the difference between Bloomberg and Statista’s numbers is likely due to differing scopes, Bloomberg’s numbers seem likely to include stevia’s usage across a variety of industries whereas Statista may only account for stevia as a sweetener). As sugar usage continues to come under questioning and governments implement sugar taxes, the importance of finding a sweetener that can satisfy in the same way as sugar is becoming ever more important for companies. With its all natural image, lack of calories, and paucity of negative research, stevia may be well placed to become the number one sugar alternative.

“There is this war on sugar waging, so stevia is in a good place,” Sara Girardello, head of high intensity sweetener research at LMC International Ltd, told Bloomberg. “Everybody is in it now.”