Sucralose vs stevia: which is better for blood sugar?

Neither sucralose nor stevia raises blood glucose on its own, and both are approved in Australia by Food Standards Australia New Zealand (FSANZ). The open questions are about gut bacteria and long-term effects. In a 2022 trial, sucralose worsened glucose tolerance in some people over two weeks, while stevia did not show that effect.

Here is how the two compare on the things people ask about most.

Does sucralose raise blood sugar?

No, sucralose on its own does not raise blood glucose. The body does not break it down for energy, and most of it passes through the gut unchanged. The National Diabetes Services Scheme (NDSS), run by Diabetes Australia, lists sucralose with the non-nutritive sweeteners, which contain no kilojoules or carbohydrate.

The packet can be a different story. Sucralose is so sweet that sachets and spoonable products need a filler. Splenda sachets sold in Australia have used dextrose and maltodextrin (Foodwatch, 2014), which are both made of glucose. The amount per sachet is small, but it is not zero.

Some small studies have looked at whether sucralose changes how the body handles sugar eaten at the same time. In a 2013 study by Pepino and colleagues in Diabetes Care, 17 people with obesity drank sucralose or water before a glucose drink. After sucralose, their glucose peaked higher and their insulin rose about 20% more. The researchers said they did not know the mechanism or whether it mattered over the long term.

Does stevia raise blood sugar?

No, stevia does not raise blood glucose. Steviol glycosides are the sweet compounds extracted from the stevia leaf, and like sucralose they provide no usable carbohydrate.

Most stevia products in Australian supermarkets are blends. Natvia, one of the best known, is made from stevia and erythritol. Erythritol is a sugar alcohol that barely raises blood glucose but adds bulk, so a blend measures more like sugar. Pure stevia drops and powders have no filler and are very concentrated.

Sugar alcohols such as erythritol, xylitol and sorbitol can cause bloating, wind and diarrhoea in larger amounts, a point the NDSS fact sheet makes for sweeteners in general. Erythritol has also come under question. A 2023 study by Witkowski and colleagues in Nature Medicine linked higher blood erythritol levels with more heart attacks and strokes in people already at risk. That was an observational study and cannot show cause, but it is a reason not to treat blends as a free pass.

“In the days prior to processed foods, sweet food meant the food was both safe and full of energy. There is no known poison that tastes sweet.”
Dr Michelle Woolhouse, Vively Medical Director

What our members' CGMs show for no-sugar drinks

Very few members log a sweetener on its own, so we looked at the next best thing: cola drunk on its own, with and without sugar. Coca-Cola Zero Sugar, for example, lists sweeteners 951 and 950 (aspartame and acesulfame potassium) rather than sucralose or stevia, so read this as a picture of non-nutritive sweeteners in general.

Half of the members who drank no-sugar cola had a typical rise under 1 mmol/L. The rise is not zero because glucose drifts up and down on its own across two hours, and some people eat things they do not log. Regular cola roughly doubled the typical rise.

This is observational data from members who chose to wear a CGM. It cannot tell us anything about gut bacteria or long-term effects, which is where the real questions about sweeteners sit. For more on the diet soft drink research, read our post on diet soft drinks and diabetes.

Do sucralose and stevia affect gut bacteria?

They can, and the effect seems to differ from person to person. The best human evidence so far is a 2022 trial by Suez and colleagues, published in Cell.

The researchers gave 120 healthy adults who did not normally use sweeteners sachets of saccharin, sucralose, aspartame or stevia for two weeks, at doses below the acceptable daily intake, or glucose or nothing as controls. All four sweeteners changed the bacteria in people's gut and mouth. The saccharin and sucralose groups also showed a significant worsening in glucose tolerance, while the stevia and aspartame groups did not.

When the team transferred gut bacteria from the people who responded most into mice, the mice developed the same glucose changes, which suggests the bacteria were part of the cause. Two weeks is short, and the trial does not tell us what happens over years, but it is the main reason we lean towards stevia over sucralose when people ask.

Do sweeteners help with weight or diabetes?

For weight, probably not much. In 2023 the World Health Organization advised against using non-sugar sweeteners, including sucralose and stevia, to control body weight or lower the risk of chronic disease. It rated the advice as conditional, because the long-term studies are observational and may be confounded, and it did not apply it to people who already have diabetes.

For people with diabetes, the NDSS says sweeteners can let you enjoy an occasional sweet food without raising blood glucose, but you do not need them to manage diabetes. It suggests using them in small amounts and checking labels, because sugar-free products can still contain carbohydrate and saturated fat.

Sweeteners are a tool for cutting back on sugar. Getting used to less sweetness is the bigger win.

“Good nutrition is not only what you put in, but also what you leave out.”
Dr Michelle Woolhouse, Vively Medical Director

Sucralose vs stevia: which should you choose?

If you want a sweetener, stevia is the slightly better choice for blood glucose and gut health on current evidence. Neither will spike your glucose, and both are far better for your blood sugar than sugar itself.

For cooking, sucralose holds up well at oven temperatures. Stevia works in drinks, sauces and dressings, but neither gives the bulk, browning or moisture sugar does, so baked goods made with them need a recipe written for that sweetener. For the bigger picture on cutting sugar, see how inverted sugar compares and how stevia stacks up against allulose.

Sucralose and stevia safety and side effects

Both are safe at normal intakes, according to FSANZ, which assesses every food additive before approval. FSANZ sets an acceptable daily intake of 15 mg per kg of body weight a day for sucralose and 4 mg per kg for steviol glycosides. A recent FSANZ review of intense sweeteners found no public health or safety issues for stevia.

The acceptable daily intake is the amount a person could have every day for life without appreciable risk.

The side effects people notice are usually gut symptoms. They tend to come from sugar alcohols in blends and sugar-free foods rather than from sucralose or stevia themselves. If a sweetener seems to upset your stomach, check the label for erythritol, xylitol, sorbitol or maltitol.

How Vively can help

A continuous glucose monitor shows how your own glucose responds to the drinks and foods you actually have, including sugar-free products that turn out to contain more carbohydrate than you thought. In the Vively CGM program, the app shows your readings against a 4 to 6 mmol/L range for people without diabetes and scores your logged meals, and you can add a dietitian review to help you cut back on sugar in a way you can keep. If you are worried about your blood sugar, start with a HbA1c test and fasting insulin, which are both in the Baseline Health Check.

Frequently asked questions

Is stevia better than sucralose?

Slightly, on current evidence. Neither raises blood glucose on its own and both are approved by FSANZ. In a 2022 trial, two weeks of sucralose worsened glucose tolerance in some healthy adults, while stevia did not. Stevia is often blended with erythritol, so check the label for what else is in the packet.

Does sucralose spike insulin?

Not on its own in most studies, but it may change the response to sugar eaten alongside it. In a small 2013 study of 17 people with obesity, drinking sucralose before a glucose drink led to a higher glucose peak and about 20% more insulin. Larger and longer studies are needed.

What are the side effects of sucralose?

Most people notice none at normal intakes. FSANZ sets the acceptable daily intake at 15 mg per kg of body weight. The open questions are about changes to gut bacteria and glucose tolerance in some people. Bloating or loose stools are more often caused by sugar alcohols in sugar-free foods than by sucralose itself.

Is stevia safe for people with diabetes?

Yes. The NDSS lists stevia among the non-nutritive sweeteners that contain no carbohydrate and do not raise blood glucose. It also says you do not need sweeteners to manage diabetes. Use them in small amounts and check labels, because stevia blends and sugar-free foods can contain other ingredients.

Which is healthier, sucralose or stevia?

Stevia has a small edge. It comes from a plant, has not shown the glucose tolerance effect seen with sucralose in the 2022 Suez trial, and FSANZ found no safety issues in its recent review. The healthiest option is getting used to less sweetness, whichever sweetener you choose.

Sources

1. Food Standards Australia New Zealand. Intense sweeteners.
2. National Diabetes Services Scheme (Diabetes Australia). Alternative sweeteners fact sheet. Version 4, November 2021.
3. Suez J, Cohen Y, Valdés-Mas R, et al. Personalized microbiome-driven effects of non-nutritive sweeteners on human glucose tolerance. Cell 2022;185(18):3307-3328.
4. World Health Organization. WHO advises not to use non-sugar sweeteners for weight control in newly released guideline. 15 May 2023.
5. Pepino MY, Tiemann CD, Patterson BW, et al. Sucralose affects glycemic and hormonal responses to an oral glucose load. Diabetes Care 2013;36(9):2530-2535.
6. Witkowski M, Nemet I, Alamri H, et al. The artificial sweetener erythritol and cardiovascular event risk. Nature Medicine 2023;29:710-718.
7. Natvia. Product information: made from stevia and erythritol.