In an effort to curb sugar intake, which has been linked to obesity, type 2 diabetes, tooth decay, and metabolic syndrome, food manufacturers looked for a way to add sweetness to their products without extra calories. And thus, zero-calorie sweeteners like Splenda stormed onto the food scene and sucralose found its way onto the ingredients lists of diet sodas and lower-cal desserts alike. But having your cake, and well, eating it too, makes you wonder if the sugar-free label is too good to be true.
As usual in the field of nutrition science, there isn’t a cut-and-dried answer on whether using Splenda or other sucralose-based products can have long-term negative effects. But here’s what we do know.
What is sucralose?
Sucralose, often recognized its brand name, Splenda, is a chemical made in a laboratory, explains Lindsey Pfau, R.D., C.S.S.D, owner of Rise Up Nutrition. It’s a non-nutritive, zero-calorie sweetener that’s very similar to sugar. “[Chemists] adjusted some of the bonds of the sugar molecule so your body doesn’t digest or absorb it,” she says.
More From Runner's World
So yes, while sucralose technically comes from a sugar molecule, it’s not to be confused with sucrose, the chemical name for table sugar. Pfau says the brand’s slogan—“Made from sugar, so it tastes like sugar”—is misleading, which has caused past legal issues. (In 2005, the Center for Science in the Public Interest released a statement saying Splenda should be more truthful in its marketing, and in 2007, the makers of Equal, whose main ingredient is aspartame, sued the makers of Splenda over the slogan for the same reason.)
“It’s clever marketing,” she says. “But it does mislead consumers because it’s passed off as a natural thing, and it’s not. The sugar molecule is natural—you can find it in foods across the Earth—but once you bring it to a laboratory and start tampering with it, it’s no longer sugar. It doesn’t function in the body like sugar.”
Regular sugar—whether that’s cane, honey, maple syrup, even high-fructose corn syrup, is absorbed and digested by the body, Pfau explains. But sucralose, which is 600 times sweeter than real sugar, doesn’t provide calories or nutrients. “It has no benefits to it, as far as affecting your body in a positive way,” she says.
So, is sucralose bad for you?
Here’s where things get a little confusing. The U.S. Food and Drug Administration says sucralose is “generally recognized as safe,” or GRAS. That means that experts consider the substance in question safe based on available research.
“All artificial sugars are GRAS, and they’re on the market because the research we have so far states that if they’re consumed in amounts that are reasonable for humans, they’re safe, that they won’t cause immediate or long-term health detriments,” Pfau says.
There is research that has found that when lab animals were given extremely high amounts of sucralose, they developed cancer. But it’s hard to replicate these studies in humans because of ethics—it could put humans at risk.
“There have been some studies of sucralose in humans, but no long-term studies that would assess whether it caused cancer or other effects over the long term,” says Lisa Lefferts, M.S.P.H., senior scientist for CSPI. “It is difficult to obtain human evidence on whether an additive causes cancer or other long-term effects. Our biggest concern with sucralose is that it causes cancer in animals, and thus may also cause cancer in humans.”
There’s also some evidence to suggest that artificially sweetened drinks may not be any healthier than sugary drinks for your heart: A 2020 research letter published in the Journal of the American College of Cardiology shows that consuming large quantities of both types of beverages are associated with higher risk of heart disease.
That said, if you’re following the mantra, “Everything in moderation,” you should be okay, both Lefferts and Pfau say.
What is the safest artificial sweetener to use?
“When it comes to cancer-causing substances, the less you’re exposed to, the lower your risk,” Lefferts says. “There is not thought to be an amount that is without risk. However, the risk is extremely small when eating small amounts, like a packet or two [of Splenda] a day.”
When it comes to making changes to your diet to improve health, zero-calorie sweeteners can serve a purpose, Pfau says.
As we previously reported, the U.S. Dietary Guidelines recommend consuming no more than 10 percent of calories from sugar. That’s about 13 teaspoons per day. The current average is 42 teaspoons.
Is sucralose ever recommended?
“As a dietitian, I might recommend or encourage people to use sucralose as a stepping stone or temporary solution to wean themselves off sugar if they’re consuming too much,” Pfau says.
If, for example, a person’s long-term goal is to lower his or her blood sugar levels, which are putting him at risk for diabetes, a zero-calorie sweetener like Splenda can satisfy a sweet tooth while not affecting weight or blood sugar, Pfau says, emphasizing that this would not be a long-term solution. Other sugar alternatives may do that job a little better, Lefferts adds.
“CSPI rates both erythritol [a low-calorie sugar alcohol] and stevia leaf extract as safe,” she says. “Erythritol would be my first choice in terms of safety, although if you consume huge amounts, it could cause nausea.”
CSPI marks sucralose, aspartame, and saccharin as unsafe based on the current research, but again, that research looked at animals, not humans.
Here’s the bottom Line
The key here—as with most aspects of nutrition—is: Everything in moderation, including zero-calorie, non-nutritive sweeteners like sucralose-based Splenda.
A can of diet soda or two a week likely won’t cause negative long-term health effects, but research has found that diet soda drinkers not only didn’t lose weight, but in many cases, they gained weight. It’s unclear why this may be, but experts suggest one reason could be because people eat more knowing they didn’t consume any calories through a diet drink.
Another theory is that when you taste sweetness from a zero-calorie sugar alternative, your pancreas secretes insulin to process that sugar. But because there aren’t any calories, your body becomes confused, disrupting the normal metabolic process.
Working with a dietitian is a good way to balance using sugar alternatives and consuming a healthy diet for a host of long-term health benefits.
As for runners who rely on sugar (the kind with calories!) to fuel their muscles for workouts, choosing sucralose won’t give their bodies what they need. You’re better off opting for the real thing and enjoying it in moderation or specifically on days when you need it, like a long run day.
“We know our bodies need calories,” Pfau says. “So we should put good calories in the body.”
Heather is the former food and nutrition editor for Runner’s World, the author of The Runner’s World Vegetarian Cookbook, and a seven-time marathoner with a best of 3:31—but she is most proud of her 19:44 5K and 5:33 mile. Her work has been published in Health.com, Bicycling, Cooking Light, Popular Mechanics, The Boston Globe, CNN, Glamour, and The Associated Press.