The Label Rule: Stevia vs Sucralose

Flip over a “zero sugar” drink, yogurt or protein bar and there’s a good chance you’ll find one of two names: stevia (often listed as steviol glycosides or Reb A) or sucralose. Both are intensely sweet, both add essentially no calories, and both have loyal fans and fierce critics online.

This week’s Label Rule puts them side by side.

What are they?

Stevia sweeteners come from the leaves of Stevia rebaudiana, a plant native to South America. The sweet compounds are called steviol glycosides; rebaudioside A (Reb A) and stevioside are the best known. They’re extracted and purified from the leaf, so the white powder in a packet is a long way from a crushed green leaf. Depending on the compound, they’re roughly 200 to 400 times sweeter than sugar.

Sucralose is made from ordinary table sugar in a multi-step chemical process that replaces three of sugar’s hydroxyl groups with chlorine atoms. That small change makes it around 600 times sweeter than sugar and means the body largely doesn’t absorb or use it for energy.

So one is plant-derived and one is manufactured from sugar. That’s a real difference, but, as we say in every Label Rule, a natural origin is not, on its own, evidence of safety, and a lab origin is not evidence of harm.

At a glance

Why are they there?

Both let manufacturers cut sugar and calories while keeping food sweet. Because they’re so potent, only tiny amounts are needed, which is why tabletop sweeteners are usually bulked out with something else to make them measurable. Check the label: common bulking agents include erythritol, dextrose or maltodextrin, and the last two do contain carbohydrate.

Stevia’s aftertaste is also why you’ll often see it blended with other sweeteners or flavourings.

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What does the evidence say?

Both are approved, with generous safety margins. The FDA sets an acceptable daily intake (ADI): an amount considered safe to consume every day over a lifetime. According to the FDA, typical consumption of these sweeteners is not expected to exceed their ADIs. To reach sucralose’s ADI, a 70 kg adult would need to consume 350 mg a day, every day, far more than most people get from food and drink.

They don’t appear to help with long-term weight control. In 2023, the World Health Organization issued a conditional recommendation against using non-sugar sweeteners as a way to control body weight. Its review found no long-term benefit for body fat in adults or children, and observational links with type 2 diabetes and heart disease, although those links may partly reflect the fact that people at higher risk are more likely to choose sweeteners in the first place. The guideline explicitly does not apply to people with existing diabetes.

Your gut bacteria may respond, differently for different people. A 2022 study in Cell gave 120 healthy adults sachets of saccharin, sucralose, aspartame or stevia for two weeks, at doses below the ADI. All four changed participants’ gut microbes. Saccharin and sucralose, on average, impaired glucose tolerance; responses varied widely from person to person. It was short and relatively small, so it raises questions rather than settling them.

Open questions about sucralose. A 2023 laboratory study reported that sucralose-6-acetate (an impurity found in sucralose and a compound formed from it in the gut) showed signs of damaging genetic material in cells in a dish. In-vitro findings don’t tell us what happens at real-world doses in people, but they merit follow-up. Separately, Germany’s Federal Institute for Risk Assessment (BfR) has advised caution about heating sucralose to high baking temperatures, because potentially harmful chlorinated compounds may form, while the data remain incomplete.

Stevia has fewer red flags, but less data on long-term use. High-purity steviol glycosides have a clean regulatory record. Note that whole-leaf stevia and crude extracts are not approved as food additives in the US.

The Label Rule verdict

Neither stevia nor sucralose is a health food, and neither is the villain it’s sometimes made out to be. Both are well within safety limits at the amounts most people consume.

If you’re choosing between them, stevia has the simpler story: a plant-derived sweetener with fewer open questions. Sucralose has a longer track record in food but more unresolved research, and it’s probably best not used for high-heat baking.

The bigger lesson from the evidence is that swapping sugar for sweeteners isn’t a shortcut to better metabolic health. Using them to step down from sugary drinks can be a sensible bridge. But the long-term goal the research points towards is simpler: getting used to food and drinks that are less sweet overall.