Better than sugar for weight and blood glucose in the short term; do not overdo it.
Review: although calorie-free sweeteners (aspartame, sucralose, saccharin, acesulfame-K...) are considered safe, their effects on the microbiota and glucose tolerance are controversial: some studies suggest alterations, others do not. Mixed evidence that depends on the sweetener.
View the study (study) →⏱ 4 min read
Non-nutritive sweeteners (also called artificial or low-calorie sweeteners) are substances that provide sweetness without the calories of sugar; the main widely used ones are aspartame, sucralose, saccharin, acesulfame K, and cyclamate (all synthetic) and stevia (steviosides and rebaudiosides, derived from the Stevia rebaudiana plant, natural but highly processed); polyols (xylitol, erythritol, sorbitol, maltitol), which provide sweetness with very few calories, are also used; the massive use of these compounds in "light/zero" drinks, "sugar-free" products, chewing gum, desserts, and other modern processed products has generated active clinical debate about their real health effects, with increasingly nuanced data that deserve careful analysis.
The most obvious and most marketed indication of non-nutritive sweeteners is replacing sugar to reduce total calorie intake and, secondarily, body weight and the metabolic problems associated with excessive sugar consumption; short- and medium-term trials show that strictly replacing sugary drinks with equivalents made with non-nutritive sweeteners does reduce calorie intake and, modestly, body weight; however, long-term data are more nuanced, with observational studies suggesting an association between regular consumption of non-nutritive sweeteners and a higher risk of obesity, type 2 diabetes, and cardiovascular events (an association that may reflect reverse causation - people with obesity or diabetes tend to use more sweeteners - or real biological effects not yet fully characterized).
An active line of research over the last ten years is the effect of non-nutritive sweeteners on the gut microbiota: several studies (especially those from the Suez and Elinav group published in Nature in 2014 and later) have documented significant changes in the composition and function of the gut microbiota with regular consumption of saccharin, sucralose, and aspartame, with changes that in some cases are associated with worse glucose tolerance and other metabolic alterations; these data suggest that the dogma that "non-nutritive sweeteners are metabolically inert" may be inaccurate, and that their effects on the microbiota could mediate part of the observational associations with worse metabolic health.
In May 2023, the World Health Organization published a new guideline recommending NOT using non-nutritive sweeteners as a weight-control strategy, based on a systematic review that concluded that long-term use shows no sustained benefits on body weight and is associated with potentially adverse effects (higher risk of type 2 diabetes, cardiovascular disease, mortality), a recommendation that represents a significant change from previous positions and deserves clinical attention.
Some sweeteners have slightly different profiles: stevia (especially in the form of leaves or less processed extracts) appears to have a more favorable or neutral profile on the microbiota and metabolism according to some studies, although highly processed commercial stevias (purified rebaudioside A) may have profiles closer to synthetic artificial sweeteners; erythritol has an interesting profile (zero effective calories, does not affect blood glucose, generally well tolerated digestively compared with other polyols) although a study published in Nature Medicine in 2023 suggested an association with a higher risk of cardiovascular events, data that require replication but add caution.
In 2023, the IARC (International Agency for Research on Cancer of the WHO) classified aspartame as "possibly carcinogenic to humans" (Group 2B), a classification that indicates limited but not dismissible evidence of carcinogenicity; the JECFA (the joint FAO/WHO committee on food additives) simultaneously maintained the acceptable daily intake (ADI) of 40 mg/kg/day as safe for most people; these parallel pronouncements generated public confusion but illustrate the nuance: aspartame at the usual doses of population consumption is probably safe for most people, but the "possibility" of carcinogenic effects at very high doses or in susceptible people cannot be completely ruled out; the reasonable clinical stance is to moderate aspartame consumption, not to demonize it absolutely but not to use it excessively without need either.
The reasonable synthesis based on current evidence suggests: prioritize water as the main drink, not drinks with sweeteners or sugar; reduce total consumption of sweet drinks (regardless of whether they are made with sugar or sweeteners); when sweeteners are used as a transition away from sugar, consider them a temporary tool, not a permanent substitute; prefer sweeteners with a more favorable profile (natural stevia, moderate erythritol) over widely used synthetic ones (aspartame, sucralose, saccharin); reduce reliance on intense sweet taste in the diet in general, a behavioral strategy that reduces the desire for sweets of any kind; in people with diabetes who need to control blood glucose, sweeteners may have a place as a transition tool, not as a sustained solution.
Generally well tolerated at usual doses for most people; the adverse effects described are rare (headache with aspartame in susceptible people, digestive discomfort with polyols if consumed in excess, especially with sorbitol and maltitol); people with phenylketonuria must absolutely avoid aspartame (it contains phenylalanine); people with irritable bowel syndrome may have significant exacerbation with polyols, especially if they have FODMAP sensitivity; in pregnancy and breastfeeding, recommendations vary by the specific sweetener but moderation is generally recommended; in pediatrics, avoiding products with non-nutritive sweeteners is probably prudent because they provide no clear advantages and may affect the calibration of taste during development; the reasonable clinical stance based on current evidence is that non-nutritive sweeteners are neither "the solution" to the sugar problem nor universal poisons, but tools with a modest clinical profile and relevant safety and metabolic considerations that advise moderation and a preference for more fundamental dietary strategies (reducing total consumption of sweet products, hydrating mainly with water, recalibrating taste toward less sweet flavors).
Information, not medical advice. Scientific evidence reflects the quality of the studies.