Sucralose
A no-calorie sweetener made from sugar by replacing three hydroxyl groups with chlorine atoms, used to sweeten foods without raising blood sugar.
Regular intake is linked to reduced insulin sensitivity and changes to gut bacteria in human trials. When heated in baking, sucralose can break down into chlorinated compounds whose safety at those doses has not been confirmed by regulators.
What is it?
Sucralose (trichlorogalactosucrose) is a synthetic, non-nutritive sweetener derived from sucrose. Three hydroxyl groups on the sucrose molecule are replaced with chlorine atoms during manufacture. The result is roughly 600 times sweeter than sugar by weight. Because the body does not fully absorb it, sucralose passes through mostly unchanged and contributes negligible calories.
What does it do?
Sucralose binds to sweet-taste receptors on the tongue and in the gut, triggering sweetness perception without providing glucose for energy metabolism. In the intestine it may interact with taste receptors that influence glucose absorption and incretin hormone release, which is the proposed mechanism for the insulin and gut-microbiome effects observed in recent trials.
Where you will see it
Diet soft drinks, squash, flavoured waters, reduced-sugar yogurts, protein bars and shakes, chewing gum, table-top sweetener sachets (often sold as Splenda), sugar-free jams, sauces and condiments, and some baked goods marketed as lower-sugar. On UK ingredient labels it appears as 'sucralose' or 'E955'.
What the science says
Insulin sensitivity and blood sugar
A 2025 randomised controlled trial in healthy adults found that 30 days of sucralose consumption produced a measurable reduction in insulin sensitivity and raised fasting glucose and insulin concentrations compared with placebo. Earlier work over ten weeks showed similar signals. The mechanism proposed is gut sweet-receptor activation altering incretin hormone release, but the full causal chain is not yet established.
30-day sucralose intake in healthy adults caused a statistically significant decrease in insulin sensitivity (approx. 20%) and increased fasting insulin and glucose, compared with placebo.
Ten weeks of sucralose consumption in healthy young adults was associated with gut dysbiosis and altered glucose and insulin levels.
Gut microbiome
Multiple human trials have found that regular sucralose intake reduces the diversity of gut bacteria (alpha diversity) and shifts species composition, including enrichment of Bacteroides fragilis and changes in short-chain fatty acids. Researchers have proposed that these shifts may contribute to low-grade gut inflammation and metabolic changes. The evidence is accumulating but the clinical significance at typical UK dietary exposure is uncertain.
Sucralose consumption in healthy adults reduced gut microbiota alpha diversity and altered short-chain fatty acid profiles relative to placebo.
Sucralose altered gut microbiota composition and was associated with liver inflammation markers in animal models.
Thermal degradation at high temperatures
When sucralose is heated to temperatures used in baking, it can break down and react to form chloropropanols, a class of chlorinated compounds with known toxicological concerns. EFSA's 2026 re-evaluation concluded that it could NOT confirm the safety of sucralose in applications requiring prolonged high-temperature processing. This is the principal outstanding regulatory gap.
EFSA confirmed the safety of sucralose at currently authorised uses but could not confirm safety for extended use in fine bakery wares due to potential thermal degradation products including chloropropanols.
Genotoxicity
Earlier regulatory reviews raised the question of whether sucralose or its thermal breakdown products might damage DNA. EFSA's 2026 re-evaluation reviewed the genotoxicity data and did not find evidence of direct genotoxicity for sucralose itself at current authorised uses. Concerns remain specifically for the thermal degradation products formed during baking.
EFSA's 2026 re-evaluation found no genotoxic concern for sucralose at currently authorised food uses, but flagged residual uncertainty around thermal breakdown products.
Where it stands with the regulators
Who should be careful
People who regularly eat sucralose-sweetened baked goods (cakes, biscuits, protein bars heated in manufacture) may be exposed to thermal degradation products whose safety has not been confirmed. Individuals monitoring blood sugar or insulin sensitivity, including those at risk of type 2 diabetes, should be aware of the emerging evidence on glycaemic effects. Look for 'sucralose' or 'E955' in the ingredients list.
The honest read
Sucralose has been in the food supply for over 25 years, and its use in drinks and cold foods has a large body of regulatory review behind it. The 2026 EFSA re-evaluation did not change its approved status for most uses. However, two threads in the science have become harder to dismiss: human RCTs now consistently show that regular sucralose intake alters gut bacteria and measurably reduces insulin sensitivity, and the specific question of what happens when sucralose is heated during baking has been left open by regulators rather than resolved. These are not settled questions, and the answers matter more for people eating sucralose-sweetened baked products daily than for those having an occasional diet drink.
Related additives
Common questions
Is E955 banned in the UK?
No. Sucralose is approved for use in the UK under the retained version of EU food additive legislation. It appears on the UK FSA approved-additives list. EFSA's 2026 re-evaluation confirmed current EU uses are authorised, though it declined to approve an extension into high-heat baking applications. The UK's authorisation rests on the pre-Brexit baseline; the FSA has not separately adopted the 2026 EFSA opinion.
Does sucralose affect blood sugar or insulin?
Emerging human trial evidence suggests it can. A 2025 randomised controlled trial found that 30 days of sucralose consumption in healthy adults reduced insulin sensitivity by around 20% and raised fasting insulin and glucose compared with placebo. The mechanism is not fully established, but gut sweet-receptor activation influencing incretin hormones is the leading hypothesis.
What foods contain E955?
Diet soft drinks, sugar-free squash, flavoured water, reduced-sugar yogurts, protein bars and shakes, chewing gum, sugar-free jams and sauces, and some lower-sugar baked goods. The table-top sweetener Splenda is primarily sucralose. Check the label for 'sucralose' or 'E955'.
Is E955 vegan?
Yes. Sucralose is synthesised from sucrose (sugar) via a chemical process and contains no animal-derived ingredients. It is suitable for vegans and vegetarians.
Sources
- EFSA re-evaluation of sucralose (E955) as a food additive, 2026
- EFSA news: EFSA finds sucralose safe when used as currently authorised, cannot confirm safety of extending its use
- UK FSA regulated products register: E-955 sucralose
- UK FSA food additives authorisation guidance: post-Brexit re-evaluation programme not in assimilated law
- Sucralose consumption modifies glucose homeostasis, gut microbiota, Curli protein and related metabolites in healthy individuals: randomised placebo-controlled triple-blind trial, Clinical Nutrition ESPEN, 2025
- Ten-Week Sucralose Consumption Induces Gut Dysbiosis and Altered Glucose and Insulin Levels in Healthy Young Adults, Frontiers in Nutrition / PubMed PMC8880058, 2022
- Gut Microbiome Response to Sucralose and Its Potential Role in Inducing Liver Inflammation in Mice, Journal of Toxicology and Environmental Health / PMC5522834, 2017
Aaron Keen is the founder of NutraSafe. He researches and writes every additive entry himself, from the primary sources. About the research →
This is a guide, not medical advice. If an additive affects you, speak to your GP or a dietitian.
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