by Nashville nutrition expert Dan DeFigio,
author of Beating Sugar Addiction For Dummies
Short answer: the major regulators consider the approved sweeteners safe at the amounts people actually eat. A 155-pound adult would need to drink roughly 9 to 14 cans of diet soda a day to exceed the international safety limit for aspartame. The more useful question is not whether they are safe, but whether they help you, and there the evidence is genuinely mixed.
What the regulators actually say
The FDA has approved six sweeteners as food additives: aspartame, acesulfame potassium (Ace-K), sucralose, neotame, advantame and saccharin. Stevia (steviol glycosides), monk fruit extract and thaumatin are separately recognised as safe. The FDA’s position is direct: its scientists “do not have safety concerns when aspartame is used under the approved conditions.”
The FDA’s acceptable daily intake for aspartame is 50 mg per kilogram of body weight per day. For a 132-pound adult, that works out to roughly 75 tabletop packets a day before you reach the limit.
The 2023 cancer headlines, in context
In July 2023 two WHO bodies published on aspartame on the same day, and the coverage collapsed them into one alarming story. They said different things.
IARC classified aspartame as Group 2B, “possibly carcinogenic to humans”, on limited evidence. That is the third of four levels. Group 2B is a statement about how confident scientists are that something could cause cancer under some conditions, not a statement about how much risk you face at normal intake. IARC itself flagged the evidence as limited and called for more research.
JECFA, the committee that actually sets intake limits, reviewed the same evidence and left the acceptable daily intake unchanged at 0 to 40 mg per kilogram of body weight. Its worked example is the number worth remembering: with a can of diet soft drink containing 200 to 300 mg of aspartame, a 70 kg adult “would need to consume more than 9–14 cans per day to exceed the acceptable daily intake, assuming no other intake from other food sources.”
The FDA disagreed with the IARC classification outright, noting that “possibly carcinogenic to humans” does not mean aspartame is actually linked to cancer, and identifying significant shortcomings in the studies IARC relied on.
So: a hazard flag that warrants more research, and a safety limit that nobody’s diet-soda habit is realistically approaching.
The question that actually matters
Here is the part the scare articles miss, and it cuts against sweeteners for a different reason.
In May 2023 WHO published a separate guideline that recommends against using non-sugar sweeteners to control body weight or reduce the risk of noncommunicable disease. It covers acesulfame K, aspartame, advantame, cyclamates, neotame, saccharin, sucralose and stevia.
Two things to hold onto. First, it is a conditional recommendation, which in WHO’s own terminology means the evidence base has limitations and the right choice may vary by person. Second, and this matters, it is not a safety finding. The guideline states plainly that it “is not based on toxicological assessments” and does not replace the intake limits set by JECFA. It applies to everyone except people with pre-existing diabetes, and it excludes sugar alcohols and personal care products.
Read properly, WHO is not saying sweeteners will hurt you. It is saying they do not appear to deliver the long-term weight benefit people switch to them expecting.
What I tell clients
Twenty years of watching people try to lose weight has left me with a fairly plain view of this.
Swapping soda for diet soda is a real improvement, and it is not the finish line
Cutting several hundred liquid calories a day is a genuine win. But most people who make that swap and change nothing else do not lose much, which is roughly what WHO’s review found across the research.
The sweet-taste habit is the thing worth working on
Whether the sweetness came with calories or not, wanting everything to taste sweet is what keeps portions high and vegetables unappealing. That is a trainable preference, and it shifts in about three weeks for most people. It is most of what we work on in nutrition coaching.
Use them as a bridge, not a destination
Diet soda while you get off regular soda: sensible. Diet soda forever, plus sweetener in your coffee, plus protein bars built on sucralose: you have swapped the calories out and kept the habit intact.
If a sweetener genuinely bothers you, stop using it
Some people report headaches or GI upset. The population-level evidence does not show a mechanism, but you do not need a peer-reviewed justification to avoid something that makes you feel bad.
Watch the sugar alcohols
Erythritol, xylitol and sorbitol are a different category and are not covered by the WHO guideline above. They cause digestive distress in a lot of people at fairly modest doses. If you have started eating “keto” bars and your stomach is unhappy, start there.
The honest bottom line
Artificial sweeteners are not poisoning you, and they are probably not doing much for you either. Neither of those is a headline, which is exactly why the internet is full of articles claiming otherwise in both directions.
If sugar is the problem you are actually trying to solve, the sweetener is a detail. Learning to handle cravings and eat mostly real food will do more for you than any decision about what is in the packet. Book a free call and we can look at what you are eating rather than what you are sweetening it with.
Frequently asked questions
Do artificial sweeteners cause cancer?
No approved sweetener has been shown to cause cancer at normal intake. In 2023 IARC classified aspartame as “possibly carcinogenic to humans” (Group 2B) on limited evidence, while the WHO committee that sets intake limits reviewed the same evidence and left the acceptable daily intake unchanged. A 70 kg adult would need more than 9 to 14 cans of diet soda a day to exceed it.
Is aspartame safe?
The FDA states it has no safety concerns when aspartame is used under approved conditions. The acceptable daily intake is 50 mg per kilogram of body weight, around 75 tabletop packets a day for a 132-pound adult.
Will switching to diet soda help me lose weight?
It removes calories, which helps. But WHO’s 2023 guideline conditionally recommends against relying on non-sugar sweeteners for weight control, because the long-term benefit has not held up in the research. Treat it as a bridge, not a strategy.
Is stevia safer than aspartame?
Both are considered safe at normal intake. Stevia is plant-derived, which many people prefer, but WHO’s recommendation on weight control covers stevia too.
Does sucralose cross the blood-brain barrier?
Most ingested sucralose is not absorbed and is excreted unchanged. The claim that it accumulates in the brain does not reflect the regulatory reviews, and the FDA continues to list sucralose as an approved additive.
What about erythritol and xylitol?
Those are sugar alcohols, a separate category not covered by WHO’s non-sugar sweetener guideline. They are generally well tolerated in small amounts but commonly cause bloating, gas and diarrhea at higher doses.
Sources
- FDA, Aspartame and Other Sweeteners in Food
- WHO, Aspartame hazard and risk assessment results released, July 2023
- IARC, Summary of findings of the evaluation of aspartame (PDF)
- WHO, Use of non-sugar sweeteners: WHO guideline, 2023
- WHO news release on the non-sugar sweeteners guideline
Written by Dan DeFigio, founder of Basics and Beyond fitness & nutrition. ACE-certified personal trainer and health coach, Sports Nutrition Counselor, Advanced Sports Nutrition Specialist, Post-Rehabilitation Conditioning Specialist. ACE faculty member and NFPT curriculum subject matter expert. Author of Beating Sugar Addiction For Dummies (Wiley).
Reviewed September 2026. This article is general nutrition education, not medical advice. If you have a specific health condition, talk to your doctor or a registered dietitian.