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Are Artificial Sweeteners Bad for You?

A WHO warning about aspartame has reignited the decades-long debate


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You know that routinely guzzling sugary drinks and scarfing down sweets is not a healthy habit. Doing so can lead to weight gain, type 2 diabetes, heart disease and other serious diseases and complications.

But is replacing all that added sugar with low- and no-calorie sweeteners any healthier? That’s a question of ongoing debate.

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On July 13, 2023, an agency within the World Health Organization (WHO) named the widely used artificial sweetener aspartame a possible cause of cancer, citing limited evidence of an increased risk for liver cancer in humans. A review by a second group within WHO found the evidence less convincing, however, and said the data “indicated no sufficient reason to change the previously established acceptable daily intake” of aspartame. The group said an adult weighing approximately 150 pounds would need to drink, for example, between nine and 14 cans of diet soda a day to exceed that limit.

“The assessments of aspartame have indicated that, while safety is not a major concern at the doses which are commonly used, potential effects have been described that need to be investigated by more and better studies,” Francesco Branca, director of WHO’s Department of Nutrition and Food Safety, said in a statement.

Aspartame has been at the center of the sweetener controversy for decades. In addition to possible cancer risk, other studies have linked it to potential health concerns, including cardiovascular disease and disruptions in the gut microbiome, a community of microorganisms that live in the digestive tract and help the body carry out various functions.

Still, the U.S. Food and Drug Administration (FDA), which approved aspartame in 1974 and has studied it since, maintains that the sweetener is safe when “used under the approved conditions.” The FDA responded in disagreement to the WHO group’s assessment, adding that it reviewed the same studies used in the evaluation and “identified significant shortcomings” in the research.

Other sweeteners under scrutiny 

study published in February 2023 in the journal Nature Medicine found a link between the sweetener erythritol and an increased risk of heart attack and stroke. Erythritol is a common sugar replacement found in many products marketed for the popular low-carb keto diet. Low amounts occur naturally in some fruits and vegetables; the body also produces low levels of erythritol to aid in energy metabolism. When used as a sweetener, however, erythritol levels are typically 1,000 times greater than levels found naturally in foods, according to a summary of the research from the National Institutes of Health.

For the study, a team of researchers from the Cleveland Clinic looked at levels of erythritol in the blood of more than 4,000 adults who were already at higher risk for cardiovascular diseases. What they found was that people with the highest levels of erythritol in their blood were more likely to have a heart attack or stroke.

A few other findings to note: When the researchers mixed erythritol with blood samples from healthy individuals, the blood platelets were more likely to clot, which can increase risk for heart attack and stroke. And when a small group of healthy individuals drank a beverage sweetened with the compound, the levels of erythritol in their blood increased 1,000-fold and remained elevated for several days.

Senior study author Stanley Hazen, M.D., points out that “the very people who are most vulnerable to heart disease” — people with type 2 diabetes or obesity, for example — are the ones who are more likely to be targeted with foods sweetened with no-calorie sugar substitutes, also called nonnutritive sweeteners. 

“And yet, by trying to [make a healthy choice], they may inadvertently be contributing to heightened risk,” says Hazen, chairman for the Department of Cardiovascular and Metabolic Sciences at the Lerner Research Institute and co-section head of preventive cardiology at the Cleveland Clinic. He emphasizes that more research is needed to better understand the potential risk.

What a Diet Soda a Day Can Do to Your Heart

An analysis of health data from more than 200,000 adults found that people who drink 2 liters or more per week (about 67 ounces) of artificially sweetened drinks — a rough equivalent of about a can of diet soda a day — have about a 20 percent higher risk of developing an irregular heart rhythm, known as atrial fibrillation, compared to people who consumed none. The risk was 10 percent higher among people who drank similar amounts of sugar-sweetened beverages, the analysis found.

Atrial fibrillation, or A-fib, is a risk factor for stroke and heart failure. More than 12 million people are expected to have the heart condition by 2030, according to the Centers for Disease Control and Prevention.

The study was published March 5, 2024, in Circulation: Arrhythmia and Electrophysiology, a peer-reviewed journal of the American Heart Association. 

“While there is robust evidence about the adverse effects of sugar-sweetened beverages and cardiovascular disease risk, there is less evidence about adverse health consequences of artificial sweeteners,” Penny Kris-Etherton, an emeritus professor of nutritional sciences at Penn State University, said in a statement from the American Heart Association. “We still need more research on these beverages to confirm these findings and to fully understand all the health consequences on heart disease and other health conditions. In the meantime, water is the best choice, and, based on this study, no- and low-calorie sweetened beverages should be limited or avoided.”

Sweeteners go by many names

A number of calorie-free sugar substitutes are on the market — some are referred to as artificial, some natural. And chances are, you’ve consumed them without realizing it.

“They’re increasingly used because consumers are concerned about sugar. And so, companies are responding to that not with the most obvious thing — making foods less sweet — but they’re using these instead,” says Dariush Mozaffarian, M.D., a cardiologist and professor of nutrition at the Friedman School of Nutrition Science and Policy at Tufts University.

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Six artificial sweeteners have been approved by the FDA:

  • Saccharin (Sweet’N Low). You can find it in sugar-free gums and candies, even toothpaste.
  • Aspartame (Equal). You can find it in popular zero-calorie soft drinks.
  • Acesulfame potassium (Sunett, Sweet One). You can find it in frozen desserts, candies, beverages and baked goods.
  • Sucralose (Splenda). You can find this in baked goods, even salad dressings.
  • Neotame (Newtame). You can find this in baked goods.
  • Advantame. This sweetener, with no brand name, is also used in baked goods.

There are others, too, that the FDA considers “generally recognized as safe” and that don’t have to go through the same safety review as those on the list above. They include:

  • Luo han guo (Monk Fruit in the Raw)
  • Purified stevia leaf extracts (Truvia)
  • Sugar alcohols, like erythritol. Sugar alcohols are neither sugar nor alcohol, but carbohydrates that have chemical characteristics of both, according to the FDA. And while they are found naturally in some fruits and vegetables, the kind you find in packaged products are commercially produced. Other than erythritol, common sugar alcohols include maltitol, sorbitol and xylitol.

These nonnutritive sweeteners pop up in a range of products, from yogurts to oatmeal to ice cream. Sometimes they’re mixed with other sweeteners.

Wondering if there’s a difference between artificial sweeteners and the so-called natural ones? Mozaffarian says “that’s a little bit of an artificial distinction,” since many of the natural options are used at levels much higher than a person would consume if they, say, ate a slice of watermelon or a handful of grapes.

“Something being natural doesn’t necessarily mean it’s safe at [high] doses,” Mozaffarian says. “At the same time, something artificial doesn’t necessarily mean that it’s harmful.”

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Should you make the sweetener switch?

There’s no doubt that cutting down on the amount of sugar you consume through foods and drinks can be a boon for your health. And most Americans have some work to do: The average U.S. adult consumes about 77 grams of sugar per day — more than three times the recommended amount for women, according to the American Heart Association.

But should you swap the real stuff for a zero-calorie alternative?

Not so fast. Mozaffarian says one way to think of nonnutritive sweeteners is more like a bridge and less like a destination. “If you’re going to have a 20-ounce soda, it’s probably better to have a diet [soda]. But, you know, better to have neither,” he says. (The WHO said in May that replacing sugar with zero-sugar sweeteners does not help with weight loss and management over the long term.)

If you’re trying to limit your intake of nonnutritive sweeteners, know that doing so can be difficult. They creep into a lot of packaged products, and many people are not familiar with all the varieties on the market. (You may have heard of aspartame — but acesulfame potassium or adventame?) What’s more, manufacturers aren’t required to include sugar alcohols, like erythritol, in the ingredient list on a food’s label.

“Sometimes you’ll see it just as natural sweeteners or natural flavors,” the Cleveland Clinic’s Hazen says.

A good rule of thumb: “If it tastes sweet and it says low-sugar, it’s likely got one of these in it,” Mozaffarian says. Packages advertised as low-calorie can be another giveaway, adds Martha Field, an assistant professor in the Division of Nutritional Sciences at Cornell University.

Many experts and organizations stress that more research on sweetener safety is needed, including long-term studies. While we wait, Field says, “it never hurts to be more aware of what you’re eating.” And if you’re concerned about the effects of sugar or sugar substitutes on your health, talk to your doctor or a dietitian, who can “help you sort through some of your personal risks,” Field adds.

Another tip to help you avoid added sugar and sugar substitutes: Stick to a diet rich in whole foods as much as possible. “I always recommend to my patients to shop the produce aisle,” Hazen says.

Editor's note: This story, originally published April 10, 2023, has been updated to reflect new information.

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