- A large Brazilian study found higher intake of several low- and no-calorie sweeteners was linked with faster decline in memory and thinking.
- The association was strongest in adults under 60 and in people with diabetes.
- The study cannot prove sweeteners caused the decline, but it raises questions about treating them as automatically harmless.
Sugar substitutes are often marketed as the sensible alternative.
They offer sweetness without the calories and without the same immediate rise in blood sugar.
But a large new study suggests the story may not be quite so clean.
Researchers followed 12,772 adults in Brazil for around eight years.
The average age at the start was 52.
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They examined seven sweeteners: aspartame, saccharin, acesulfame K, erythritol, xylitol, sorbitol and tagatose.
These sweeteners are commonly found in diet drinks, flavoured waters, energy drinks, yoghurts, low-calorie desserts and tabletop sweeteners.
Participants completed food questionnaires, then underwent repeated cognitive testing over time.
Those consuming the largest total amounts of sweeteners had a 62% faster decline in overall thinking and memory than those consuming the smallest amounts.
Researchers estimated this was equivalent to around 1.6 extra years of cognitive ageing.
The middle-intake group also declined faster than the lowest-intake group.
The association was strongest in adults under 60.
It was also stronger among people with diabetes.
That is important because people with diabetes are often encouraged to reduce sugar and may use sweeteners more frequently.
When researchers looked at individual sweeteners, six were linked with faster decline in overall cognition, particularly memory.
These were aspartame, saccharin, acesulfame K, erythritol, sorbitol and xylitol.
Tagatose was the only sweetener in the study not linked to cognitive decline.
The caveat is crucial.
This was observational research.
It cannot prove sweeteners caused the cognitive changes.
People who consume more sweeteners may differ in other ways, including diabetes status, diet quality, weight, medication use and broader health risk.
Dietary intake was also self-reported, which is never perfect.
Still, the findings are worth taking seriously.
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Low-calorie does not automatically mean neutral.
Artificial and low-calorie sweeteners may have biological effects that go beyond sugar replacement.
For now, the most sensible advice is moderation.
Replacing large amounts of sugar with large amounts of sweetener may not be the win people assume.
The stronger long-term goal is to reduce dependence on intensely sweet foods and drinks altogether.
