The Main Sweeteners You'll Actually See
"Sugar-free" is a catch-all term covering several genuinely different compounds with different origins, sweetness levels, and regulatory histories, roughly split into two camps: synthetic sweeteners built in a lab, and plant-derived extracts marketed as a more natural alternative.
Aspartame
Roughly 200 times sweeter than sugar, used in many diet colas since the 1980s and one of the most extensively studied food additives in existence. The subject of a significant 2023 WHO health classification, covered in detail below.
Sucralose
Derived from sugar itself through a chemical process that substitutes certain molecules, roughly 600 times sweeter than sugar, and generally more heat-stable than aspartame during manufacturing, which is part of why it's used so widely.
Acesulfame K
Often used alongside aspartame or sucralose in blends, since combining sweeteners can produce a more rounded, sugar-like taste than any single one used alone, masking the slight bitterness some sweeteners carry individually.
Stevia
Extracted from the leaves of the stevia plant, native to South America, and marketed heavily as "natural" — though the extraction and refining process needed to isolate its sweet compounds is still fairly involved before it ever reaches a drink.
Monk Fruit Extract
A newer entrant to UK shelves, extracted from a small fruit traditionally used in Chinese medicine for centuries, often blended with other sweeteners to balance production cost and final taste.
What Actually Happened With Aspartame in 2023
On the same day in July 2023, two separate WHO-affiliated bodies published two different findings after reviewing the same body of evidence. The International Agency for Research on Cancer (IARC) classified aspartame as "possibly carcinogenic to humans" — Group 2B, the same category as pickled vegetables and aloe vera, based on what it described as limited evidence, specifically for one type of liver cancer. On the very same day, the Joint FAO/WHO Expert Committee on Food Additives (JECFA) reviewed that same research and reaffirmed the existing acceptable daily intake at 40mg per kilogram of body weight, finding no reason to tighten safety limits for typical consumers.
In practical terms, that daily limit works out to roughly 10 cans of diet soda a day for a 70kg adult before approaching the threshold — a volume far beyond typical everyday consumption for almost anyone. The US FDA publicly disagreed with IARC's classification entirely, citing significant limitations in the underlying human studies used to reach it. It's a genuine case of two expert bodies reviewing identical evidence and reaching different, non-contradictory conclusions: one about theoretical hazard under some conditions, the other about real-world risk at the levels people actually drink.
Direct summary from the World Health Organization, published 14 July 2023, jointly with the IARC and JECFA committee findings.
Does "Natural" Actually Mean Better Here?
Not necessarily. Stevia and monk fruit come from plants, but by the time they're refined into a concentrated sweetening extract used in a can of soda, they've been through significant industrial processing — they aren't simply crushed leaves or fruit added straight to water in their original form. "Natural origin" and "minimally processed" are genuinely different claims, and it's worth not automatically assuming plant-derived sweeteners are inherently healthier or safer just because of where the raw ingredient started out.
Why This Category Exploded in the UK Specifically
The sheer range of sugar-free options now available on UK shelves isn't a coincidence, and it didn't happen gradually over decades — it accelerated sharply within a fairly short window. Since the Soft Drinks Industry Levy took effect in 2018, manufacturers have had a direct financial incentive to reformulate below the taxable sugar threshold, and swapping sugar for one of these sweeteners is by far the simplest, fastest way to do it without changing a product's core branding or identity. We cover exactly how that levy works, and what it does and doesn't tax, in our guide on what separates juice from soft drinks under UK law.
Reading the Label With Confidence
Sweeteners are legally required to be named on UK ingredient lists — check for aspartame, sucralose, or acesulfame K by name.
Products containing aspartame must carry a specific warning for people with phenylketonuria (PKU), a rare genetic condition.
"No added sugar" and "sugar-free" aren't identical claims — check which specific wording is actually printed on the can before assuming either applies.
If avoiding a specific sweetener matters to you personally, check the full ingredients list rather than just the front-of-pack claims, which rarely name the sweetener used.
Read the Full Guide
Are Juice and Soft Drinks the Same Thing? →
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