What the Research Says About Artificial Sweeteners

Low- and no-calorie sweeteners are in diet sodas, sugar-free gum, yogurts, protein bars and tabletop packets, and the headlines about them swing from reassuring to alarming. Part of the confusion is that "artificial sweetener" covers very different substances with different evidence behind them. Taking them one at a time makes the picture clearer.

A useful number to know is the acceptable daily intake, or ADI, set by regulators. It is the amount a person could consume every day over a lifetime without appreciable risk, and it is deliberately set far below the doses that caused any effect in studies. Most people consume well under the ADI for any single sweetener.

Aspartame

Found in many diet sodas and sold as Equal and NutraSweet. In 2023, the World Health Organization's cancer research agency, IARC, classified aspartame as "possibly carcinogenic to humans", its weakest category, based on limited evidence. At the same time, the WHO and FAO expert committee on food additives reviewed the same evidence and kept the acceptable daily intake at 40 milligrams per kilogram of body weight. For a 70-kilogram adult, that would mean drinking many cans of diet soda every day. The US Food and Drug Administration said it disagreed with the IARC classification. People with the rare inherited condition phenylketonuria must avoid aspartame, which is why products carry a warning.

Sucralose

Sold as Splenda and widely used in baking because it stays stable when heated. It is approved in the US and Europe. Some laboratory and small human studies have raised questions about effects on gut bacteria and blood sugar responses, but results are inconsistent and the doses often higher than typical intake.

Saccharin

The oldest, sold as Sweet'N Low. It carried a cancer warning label in the US from the late 1970s after studies in rats, but later research found the mechanism did not apply to humans, and the warning requirement was removed in 2000.

Acesulfame potassium

Often labeled Ace-K and usually blended with other sweeteners in drinks. It is approved in the US and Europe, and research on it in humans is more limited than for aspartame or sucralose.

Stevia and monk fruit

Both come from plants, and both are often described as natural. Purified steviol glycosides from the stevia leaf, and monk fruit extract, are generally recognized as safe by the FDA. The highly purified forms in products are processed extracts, not ground leaves or fruit, and long-term research on them is thinner than for the older sweeteners.

Erythritol and other sugar alcohols

Sugar alcohols such as erythritol, xylitol and sorbitol are common in sugar-free gum, chocolate and keto products. In large amounts they can cause bloating and diarrhea. A 2023 study published in Nature Medicine linked higher blood levels of erythritol to a greater risk of heart attack and stroke and found it made platelets more prone to clotting in laboratory tests. The study showed an association rather than proof of cause, but it has prompted further research. Xylitol is also highly toxic to dogs, so keep products containing it out of their reach.

Do they help with weight?

In short-term controlled trials, swapping sugary drinks for diet versions tends to produce modest weight loss. Over the long term the evidence is less clear, and in 2023 the WHO issued a guideline advising against using non-sugar sweeteners as a means of weight control, suggesting other ways to reduce sugar instead. The guideline does not apply to people with existing diabetes.

A practical view

For someone replacing several sugary drinks a day, a switch to diet versions is a reasonable step, especially with diabetes, where sweeteners do not raise blood sugar the way sugar does. Water, sparkling water and unsweetened tea or coffee are better still. Gradually reducing how sweet your food and drinks are tends to lower the craving for sweetness over time. If you have a specific health condition, a doctor or registered dietitian can give advice that fits it.