Artificial sweeteners aren’t hard to find. They sweeten diet drinks, protein products, flavored yogurt and other foods labeled “sugar-free” or “zero sugar.” They can also be found in products that don’t advertise themselves as lower- or zero-sugar. Artificial sweeteners can cut added sugar and calories, and they have little immediate effect on blood sugar — but their long-term health effects are harder to pin down.

Short-term studies suggest artificial sweeteners may be useful when they replace sugar. Longer observational studies have linked frequent use with type 2 diabetes, heart problems and some cancers, but they cannot prove the sweeteners caused those outcomes.

Lea Obeid, a registered dietitian with Houston Methodist, says no single answer applies to every person or product. Whether an artificial sweetener is useful depends on why someone chooses it and how that choice fits into the person’s overall eating pattern.

What are artificial sweeteners?

Artificial sweeteners are synthetic ingredients that add sweetness with few or no calories in the amounts typically used. Common examples include:

• Acesulfame potassium, also called acesulfame K or Ace-K

• Aspartame

• Saccharin

• Sucralose

Artificial sweeteners fall within a broader category of ingredients used in place of sugar.

“Sugar substitute is an umbrella term for anything sweet that you would use to replace regular sugar,” Obeid says. “Artificial sweeteners are one type of sugar substitute, but not all sugar substitutes are artificial sweeteners.”

Stevia and monk fruit are non-nutritive sweeteners derived from plants or fruit. Xylitol and erythritol are sugar alcohols. The body processes each category differently, so research on one sweetener may not apply to another.

When can artificial sweeteners be useful?

An artificial sweetener can change the amount of sugar, calories or carbohydrates in a food or drink. Whether that change is useful depends on the person’s goal and what happens elsewhere in the diet.

If the goal is to cut added sugar

Americans consume a lot of added sugar — people ages 2 and older get about 12-13% of their total daily calories from added sugars. The American Heart Association recommends limiting added sugars: men should consume no more than 36 grams or 150 calories of sugar a day, and women should limit themselves to 25 grams or 100 calories or less.

Because artificial sweeteners are much sweeter than sugar, only a small amount may be needed. The amount used in one serving can provide few or no calories.

“From a calorie perspective, artificial sweeteners can be helpful for someone who is trying to reduce their overall intake,” Obeid says. “They can also help lower added sugar while maintaining sweetness.”

Sugar-sweetened beverages account for about 24% of the top sources of added sugars in the American diet. Replacing several sugar-sweetened drinks a day with artificially sweetened versions could substantially reduce added sugar and calories. Choosing artificially sweetened products in addition to the rest of your usual diet may not.

A science advisory from the American Heart Association, supported by the American Diabetes Association, addressed low-calorie drinks as replacements for sugar-sweetened beverages. The advisory concluded that these drinks may be useful for adults who regularly consume large amounts of sugary beverages. Water remains the preferred option, but a low-calorie drink may offer an alternative for someone who is not ready to make that switch.

The advisory applies to drinks, not every artificially sweetened food. It also notes that the calorie benefit may be lost if a person consumes more calories from other sources. Changing the sweetener does not change the rest of the food.

If the goal is to manage blood sugar

Regular sugar is a carbohydrate that the body breaks down into glucose. Artificial sweeteners generally aren’t processed the same way, or are used in amounts too small to contribute a meaningful amount of carbohydrates.

“Artificial sweeteners have minimal to no effect on blood sugar levels,” Obeid says. “That can help someone maintain sweetness while reducing the amount of added sugar they consume.”

For someone with diabetes or prediabetes, the immediate effect on blood sugar may carry more weight in the decision.

“With diabetes or prediabetes, the amount and timing of carbohydrates matter,” Obeid says. “Artificial sweeteners may offer another option, but the individual’s goals and overall eating pattern still need to be considered.”

A “sugar-free” food is not necessarily carbohydrate-free. Flour, milk and other ingredients may contribute carbohydrates even when a product contains an artificial sweetener. The total carbohydrate line on the Nutrition Facts label includes carbohydrates from the full product, not only added sugar.

Substantial changes in carbohydrate intake may affect the needs of people who take insulin or other blood sugar-lowering medication. A physician or registered dietitian can help account for those changes.

If the goal is weight loss

Artificial sweeteners may lower calorie intake when they replace sugar directly. That does not mean they produce lasting weight loss on their own.

In May 2023, the World Health Organization released a guideline examining whether non-sugar sweeteners should be used for long-term weight control or to reduce the risk of chronic disease. The guideline covers artificial sweeteners such as aspartame and sucralose, as well as non-nutritive sweeteners derived from natural sources, including stevia. It does not include sugar alcohols such as xylitol or erythritol.

The WHO recommended that people without diabetes not rely on non-sugar sweeteners for those purposes. The recommendation is conditional because the organization rated the evidence as uncertain. It does not mean the review found approved sweeteners to cause disease, and it does not change established safety limits for individual sweeteners.

Trials reviewed by the American Heart Association found modest weight differences when low-calorie sweetened beverages replaced sugary drinks. Some included other changes, such as drinking more water or receiving weight-management support, so researchers could not always isolate the effect of the low-calorie beverage.

In the evidence review behind the WHO recommendation, shorter trials also found small weight differences mainly when non-sugar sweeteners replaced sugar and reduced calorie intake. Comparisons with water showed no weight advantage, and most trials lasted three months or less.

Longer observational studies have linked greater use to a higher body mass index or increased risk of obesity. Some of the association may run in the other direction. A person who already has excess weight or related health concerns may be more likely to choose diet products. Researchers call this reverse causation.

Switching one product will not necessarily reduce total daily calorie intake. Any effect on weight depends on whether the substitution changes overall calorie intake.

What do we know about the long-term health questions?

The long-term research on artificial sweeteners is less clear than their immediate effects on calories or blood sugar. Some studies have found associations with type 2 diabetes, heart problems and cancer, but the results vary by sweetener, health outcome and how the research was conducted.

Type 2 diabetes and heart health

Observational studies have associated higher artificial sweetener intake with type 2 diabetes and heart problems. The findings do not prove that artificial sweeteners caused those conditions.

A 2023 study published in Diabetes Care followed more than 105,000 French adults for about nine years. Higher intake of artificial sweeteners, including aspartame, acesulfame potassium and sucralose, was associated with a greater likelihood of developing type 2 diabetes. Although the researchers accounted for many differences in health, diet and lifestyle, people with existing health concerns may still have been more likely to choose artificial sweeteners.

A review published in The American Journal of Medicine combined findings from 16 prospective studies involving more than 1.4 million people. Greater intake of artificially sweetened beverages was associated with more cardiovascular events. The studies differed in how they measured intake and health outcomes. People with a higher risk of heart disease also may have been more likely to choose low-calorie drinks.

The American Heart Association has noted similar limitations in observational research. Long-term randomized trials that measure events such as heart attacks, strokes or deaths are limited.

Research has not determined whether frequent artificial sweetener use contributes directly to type 2 diabetes or heart disease. It also has not identified an amount at which occasional consumption causes either condition.

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Do artificial sweeteners cause cancer?

Research has not established that artificial sweeteners approved for use in the U.S. cause cancer in people. Findings from human studies are inconsistent and vary by sweetener and cancer type.

The National Cancer Institute reports that some studies have found associations between artificially sweetened beverages and certain cancers, while others have not. An umbrella review that accounted for the quality of previous reviews found only weak evidence of an association with developing or dying from cancer overall.

In 2023, the International Agency for Research on Cancer classified aspartame as “possibly carcinogenic to humans.” The classification was based on limited evidence, primarily involving liver cancer. The working group could not confidently rule out chance, bias or other differences among participants as explanations for the findings.

The phrase “possibly carcinogenic” describes the strength of evidence that a substance could cause cancer under some circumstances. It does not show how likely cancer is at the amounts people normally consume.

The Joint FAO/WHO Expert Committee on Food Additives conducted a separate assessment focused on expected exposure. It concluded that the evidence linking aspartame consumption with cancer in people was not convincing and retained the existing acceptable daily intake. The American Cancer Society supports further study while noting that commonly consumed amounts are not considered a major safety concern.

Do artificial sweeteners affect the gut microbiome?

Artificial sweeteners may affect the gut microbiome, but human research has not established that they consistently change gut bacteria or cause health problems. The gut microbiome is the community of microorganisms living in the digestive tract. Its makeup can be influenced by diet, medication and many other factors.

“Some studies suggest that non-nutritive sweeteners may alter the gut microbiome and affect the body’s blood sugar response,” Obeid says. “The evidence is still limited, and the effect may depend on the sweetener.”

Most of the research in this area has been conducted in animals rather than people.

In a 2021 study published in the Journal of Gastroenterology and Hepatology, acesulfame potassium was shown to produce changes in gut bacteria, inflammation, increased intestinal permeability and small-intestine injury in animals. The dose was higher than the amount people typically consume. The researchers also could not determine whether the bacterial changes caused the intestinal damage.

A 2022 animal study published in Frontiers in Nutrition reported changes in gut bacteria and the intestinal barrier after several doses of sucralose. The animal subjects did not gain weight, and the researchers noted that the findings may not apply to human metabolic health.

The findings may help guide human studies, but they cannot predict whether a particular sweetener or amount will affect an individual’s gut.

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Why the guidance on artificial sweeteners sounds conflicting

Guidance on sweeteners can sound inconsistent because organizations do not always evaluate the same use or health outcome. Replacing regular soda with a diet soda is a different question from using artificial sweeteners for long-term weight control. Cancer agencies and food-safety committees consider other types of evidence.

The American Heart Association examined low-calorie drinks as replacements for sugary beverages. It found that these drinks may be useful for adults who regularly consume large amounts of sugar-sweetened beverages. It did not evaluate artificial sweeteners as a long-term way to prevent disease.

The World Health Organization examined whether people should use non-sugar sweeteners for long-term weight control or to reduce the risk of chronic disease. Its 2023 guideline recommends that people without diabetes not rely on them for those purposes. The recommendation is conditional because the organization rated the evidence as uncertain and acknowledged that existing differences among sweetener users may have influenced the findings. People with pre-existing diabetes were outside the scope of the WHO recommendation — it did not evaluate non-sugar sweeteners as part of diabetes management, and it excluded studies conducted only in people with diabetes from its review. The exclusion is not an endorsement or a conclusion about the sweeteners’ long-term effects for people with diabetes.

Cancer organizations and food-safety committees also examine separate questions. The International Agency for Research on Cancer evaluated whether aspartame could present a cancer hazard under some circumstances. The Joint FAO/WHO Expert Committee on Food Additives assessed risk at expected exposure levels.

These differences in scope help explain why a sweetener can be approved for use, classified as a possible hazard and not recommended as a long-term weight-control strategy. None of those findings determines whether an artificially sweetened product is the right choice for a particular person.

How to decide whether to use artificial sweeteners

What the artificial sweetener would replace is central to the decision: a daily sugar-sweetened drink presents a different opportunity than the few slices of birthday cake you might have once a year. And, for individuals living with prediabetes or diabetes, artificial sweeteners can be a way to enjoy some foods without significantly affecting their blood sugar.

That said, a “zero sugar” label alone does not determine whether a food or drink fits someone’s needs. Serving size, total carbohydrates, protein, fiber, sodium and saturated fat provide more information about what the food or drink offers.

“When selecting between products or deciding whether to use actual sugar versus an artificial sweetener depends on personal preference and whether the person enjoys the taste, but also if the person is living with diabetes,” Obeid says. “I’m very big on maintaining the taste of food because food is pleasure, and you still want to enjoy the food that you’re having.”

Obeid says a general rule for evaluating whether a product is high in added sugars is to look at the Nutrition Facts label: anything between 0 and 5 grams is low, 5 to 9 grams is medium, and anything in double digits is high. From there, think about how often and how much of a product you might consume. As the saying goes, the dose makes the poison.

Plus, Obeid recommends noticing whether highly sweetened products affect other food choices.

“Some artificial sweeteners are 200 times sweeter than sugar,” Obeid says. “Regular exposure to such intense levels of sweetness may condition the palate to prefer increasingly sweet flavors, potentially making naturally sweet foods seem less satisfying and increasing one’s tolerance for sweetness.”

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This is a practical consideration, not a proven biological effect that will occur in everyone. Taste preferences and responses to various sweeteners differ.

If an artificially sweetened version of a food is not satisfying, a smaller amount of regular sugar may be a better choice. Water and unsweetened drinks can also reduce added sugar without replacing it with another sweetener.

Research has not identified a precise amount that separates harmless from harmful use.

“I don’t think people need to go to the extreme of choosing no-sugar versions of everything,” Obeid says. “Think about how frequently you eat the food and how much you have at one time.”