The Eternal Letdown of Sugar Substitutes

A few months ago, my doctor uttered a phrase I’d long dreaded: Your blood sugar is too high. With my family history of diabetes, and occasional powerful cravings for chocolate, I knew this was coming and what it would mean: To satisfy my sweet fix, I’d have to turn to sugar substitutes. Ughhhh.

Dupes such as aspartame, stevia, and sucralose (the main ingredient in Splenda) are sweet and have few or zero calories, so they typically don’t spike your blood sugar like the real thing. But while there are now more sugar alternatives than ever, many people find that they taste terrible. The aspartame in Diet Coke leaves the taste of pennies in my mouth. And in large amounts, substitutes are bad for you: Last year, the World Health Organization warned that artificial sweeteners could raise the risk of certain diseases, singling out aspartame as “possibly carcinogenic.”

But last week, I sipped a can of Arnold Palmer with a brand-new sweetener that promised to be unlike all the rest. The drink’s strong lemon flavor was mellowed by a light, unremarkable sweetness that came from brazzein, a sugar substitute green-lighted by the FDA last month. Oobli, a California-based company that sells the lemonade-iced tea and manufactures brazzein (which occurs naturally in West Africa’s oubli fruit), has billed it as a “revolution in sweetness.” Yet like everything that came before it, brazzein is far from perfect: To help mask its off taste, the can had some real sugar in it too. For now, Eric Walters, a sweetener expert at Rosalind Franklin University, told me, brazzein is just “an alternative” to the many options that already exist. None has come even close to the real deal.

The ideal sugar alternative is more than just sweet. It must also be safe, taste good, and replicate the distinct way sugar’s sweetness develops on the tongue. In addition to aspartame and other synthetic sugar alternatives that have existed for more than a century, the past two decades have brought “natural” ones that are plant-derived: sweeteners made with stevia or monk fruit, which the FDA first approved in 2008 and 2010, respectively, can now be readily found in beverages such as Truly hard seltzer and Fairlife protein shakes. Stevia and monk fruit have been used “for hundreds of years by the people who live in the regions where they grow, so I don’t have huge worries about their safety,” Walters told me.

All of these sweeteners work in basically the same way. Chemically, molecules other than just sugar can bind to the tongue’s sweet receptors, signaling to the brain that something sweet has landed. But the brain can tell when that something is not sugar. So far, no sweetener has accomplished that trick; off flavors that sometimes linger always give away the ruse.

The problem is that sugar alternatives are like celebrity impersonators: aesthetically similar, reasonably satisfying, but consistently disappointing. Take stevia and monk fruit: By weight, they’re intensely sweet relative to table sugar—monk fruit by a factor of up to 250 and stevia by a factor of up to 400. Because only a tiny amount is needed to impart a sweet taste, those sweeteners must be bulked up with another substance so they more closely resemble sugar granules. Manufacturers used to add carbohydrates such as corn starch—which are eventually broken down into sugars—but they now use erythritol, a calorie-free sugar alcohol, which “doesn’t count as sugar at all,” Walters said.

The end products look and feel similar to sugar, but not without downsides. Erythritol has been linked to an increased risk of heart attack and stroke. And stevia and monk-fruit sweeteners come with an aftertaste that has been described as “bitter,” “unpleasant,” and “disastrous.” When Walters first helped produce stevia 35 years ago, “the taste quality was so awful that we thought no one would buy it,” he said. “But we underestimated how much people would put up with it because it was ‘natural.’”

Brazzein is yet another natural option. Unlike other sugar substitutes, brazzein is a protein, but it is still intensely sweet and low in calories. It is so sweet—about 1,000 times sweeter than sugar—that some gorillas in the wild have learned not to waste their time eating it. That protein has become a health buzzword certainly won’t hurt Oubli’s sales, but its products won’t bolster any biceps: Its teas contain very little—about 1 percent—because brazzein’s sweetness is so potent.

Last month, Oobli received a “no questions asked” letter from the FDA, which means that the agency isn’t concerned about the product’s safety. Oobli’s iced teas and chocolates are the first brazzein-sweetened products to be sold in the U.S., although the sweet protein was identified three decades ago. Thaumatin, another member of the sweet-protein family, has been in use since the 1970s, though mostly as a flavor enhancer. One reason it took brazzein so long to be marketable is that it occurs at such low levels in the oubli fruit that mass-producing it was inefficient. Instead of harvesting brazzein from fruit, Oubli grows the protein in yeast cells, which is more scalable and affordable, Jason Ryder, Oobli’s co-founder and chief technology officer, told me.

One distinction between brazzein and other sweeteners is its chemical size. Compared with sugar, stevia, and monk fruit, brazzein molecules are relatively large because they are proteins, which means they aren’t metabolized in the same way, Ryder said. The effects of existing sweeteners on the body are still being investigated; although they are generally thought to not hike blood sugar or insulin, recent research suggests that they may in fact do so. That may never be a concern with brazzein, Grant DuBois, a sweetener expert and the chief science officer at Almendra, a stevia manufacturer, told me.  

The most compelling upside of brazzein may be that it tastes pretty good. My palate, which is extra sensitive to artificial sweeteners, wasn’t offended by the taste. Would drink again, I thought. But the glaring caveat with Oobli’s teas is that they do contain some actual sugar—just less than you’d expect from a regular drink. The sugar helps mitigate a feature of brazzein’s sweetness, Ryder said.

One of the enduring problems with brazzein and many other popular sugar alternatives is that their sweetness takes more time than usual to develop, then lingers longer than expected. Indeed, although I liked the Arnold Palmer as it went down, I felt a peculiar sensation afterward: a trace of sweetness at the back of my throat that intensified, and felt oddly cool, as I exhaled. It was not unpleasant, but it was also reminiscent of having accidentally swallowed minty gum. If Diet Coke were made with brazzein instead of aspartame, Walters explained, you’d taste caffeine’s bitterness and the tartness of phosphoric acid before any sweetness, and when all of those flavors dissipated, the sweetness would hang around. “It’s just not what you want your beverage to be,” he said.

Balancing brazzein with a touch of sugar achieves the goal of reducing sugar intake. But most of the time, people who seek out products sweetened with sugar alternatives want “zero sugar,” DuBois said, “so that’s not really a great solution to the problem.” The perfect sweetener would wholly replace all of the sugar in a food, but brazzein probably won’t get there unless the peculiarities of its sweetness can be fully addressed. “If I knew how, I could probably make millions of dollars,” Walters said.

The future of sugar substitutes may soon offer improvements rather than alternatives. Last year, DuBois and his colleagues at Almendra published a peer-reviewed paper describing a method to speed up slow-moving sweetness by adding a pinch of mineral salts to sweeteners, which helps them quickly travel through the thick mucus of the tongue, resulting in a vastly improved experience of sweetness. “It works with stevia, but also aspartame, sucralose, monk fruit—it works very well with everything we’ve tried,” Dubois said, noting that it would probably also work with brazzein. With the right technology, sweeteners, he said, can become “remarkably sugarlike.”

Yet searching for the perfect sugar alternative is a fool’s errand. No matter how good they get, a single substance is unlikely to satisfy all tastes and expectations about health. As my colleague Amanda Mull wrote when aspartame was deemed carcinogenic over the summer, there’s always something. Much is left to be learned about the health effects of natural sweeteners, which may not be as natural as they seem; some stevia products, for example, are chemically modified to taste better, Walters told me

More than anything, sweeteners exist so that people can indulge in sweet treats without needing to worry about the consequences. They can address most of sugar’s problems—but they can’t do everything. “If you pick one sweetener and put it in everything, and drink and eat it all day long, that’s probably not a good thing for you,” Walters said. A sugar-free, flawlessly sweet chocolate may someday come to exist, but I’ll probably never be able to gorge on it without dreading my next blood test.