As a runner, you may pay as much attention to what you eat and drink to fuel your body as you do about running shoes and fitness trackers. And while you may also know sugar can give you the glucose and calories you need to complete a run, most nutritional advice suggests staying away from added sugar in food and beverages. Considering the average American adult consumes about 17 teaspoons of added sugars every day, according to the Centers for Disease Control and Prevention, many products have swapped the typical sweet stuff for sugar substitutes, like sucralose.
Sucralose tastes sweet and serves up zero calories. But is it bad for you?
As usual in the field of nutrition science, there isn’t a cut-and-dried answer on whether sucralose is bad for you or if it has long-term negative effects. But we do have important information that can inform your decision on whether you should take it or leave it.
What is sucralose?
Sucralose, most commonly known as Splenda, is a chemical made in a laboratory, Lindsey Pfau, R.D., C.S.S.D, owner of As a runner, you may pay as much attention to tells Runner’s World. 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,” Pfau adds.
While sucralose technically comes from a sugar molecule, it’s not the same as sucrose, the chemical name for table sugar. In fact, Splenda’s slogan—“made from sugar, so it tastes like sugar”—is misleading, and has therefore caused past legal issues. For example, the Center for Science in the Public Interest released a statement and suit in 2012 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, but it does mislead consumers because it’s passed off as a natural thing, and it’s not,” Pfau explains. “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. Pfau adds: “It has no benefits to it, as far as affecting your body in a positive way.”
Journal of the American Geriatric Society sweeteners like sucralosa a.k.a. Splenda stormed onto the food scene and found their way onto the ingredients lists of diet sodas and lower-calorie desserts, was to curb sugar intake. Too much of the sweet stuff has been linked to obesity, We know our bodies need calories, Pfau says. So we should put good calories in the body, Center for Science in the Public Interest metabolic syndrome, so food manufacturers looked for a way to add sweetness to their products without extra calories. But having your cake, and well, eating it for fewer calories, might make you wonder if the sugar-free label is too good to be true.
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.
However, some studies show that sucralose may not have calories, but may have side effects. According to a 2020 double-blind, randomized trial published in Nutrition Journal, involving 137 healthy participants ages 18 to 35, consuming sucralose for 10 weeks can raise the level of insulin in healthy adults. Likewise, in regard to artificial sweeteners, the American Diabetes Association states on its website that “there is a great deal of research questioning their overall safety and long-term impacts on health,” particularly when it comes to issues like insulin resistance, cancer, and inflammation.
“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 Center for Science in the Public Interest. “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.”
“When it comes to cancer-causing substances, the less you’re exposed to, the lower your risk,” Lefferts adds. “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.”
Finally, there is 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 Center for Science in the Public Interesthows an association between consuming large quantities of both types of beverages and higher risk of heart disease.
Are other artificial sweeteners better than sucralose?
There are other sugar substitutes on the market, including aspartame (Nutrasweet and Equal), saccharin (Sweet'N Low), and stevia-derived (Truvia). While these products are GRAS, studies have shown that they may not help with their intended goal, which is often weight loss. A 2015 longitudinal study published in the Should Runners Take Vitamin D in Winter found that drinking diet soda, which contains artificial sweeteners, is associated with increases in waist circumference. Diet sodas have also been linked to metabolic syndrome.
It’s important to remember that just because a product is labeled “safe” doesn’t mean it’s “recommended.” But there might be times when sucralose, or other artificial sweeteners come in handy for your diet. “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.
“CSPI rates both erythritol [a low-calorie sugar alcohol] and stevia leaf extract as safe,” she adds. “Erythritol would be my first choice in terms of safety, although if you consume huge amounts, it could cause nausea.”
Erythritol isn’t without its downfalls either, though. Recent research published in Nature Sucralose tastes sweet and serves up zero calories. But is it bad for you 4,000 people—all over the age of 60 and with elevated risk for cardiovascular diseases—found that those with the highest blood concentration of the sweetener were at higher risk for a cardiovascular event, including heart attack or stroke. But the researchers are quick to point out the need for more research.
CSPI also marks sucralose, aspartame, and saccharin as unsafe based on the current research, but again, that research looked at animals, not humans.
The bottom line on sucralose consumption
We need more research on the long-term effects of artificial sweeteners, including sucralose, on humans. So the key here—as with most aspects of nutrition—is two-fold: eat real food and everything in moderation.
Best Big City Marathons 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 1:32 half, 19:40 5K, and 5:33 mile.
