Are Artificial Sweeteners Safe? Aspartame, Diet Drinks and the Sweetener in Your Tea
In 2023 the headlines said aspartame 'may cause cancer', and two months earlier the WHO had advised against using sweeteners for weight loss. So should you switch back to sugar in your tea, or stop the Diet Coke? Here is what each finding actually means, what the trials show for weight, and a simple way to decide.
By Taha Raza
Published
In Pakistan, sweeteners mostly show up in two places: diet soft drinks, and the small tablets or sachets people with diabetes or on a diet drop into their tea. When the aspartame headlines appeared, many people quietly went back to sugar. That is the one choice the evidence clearly does not support.
Does aspartame cause cancer?
In July 2023 two WHO bodies reviewed aspartame. The International Agency for Research on Cancer classed it as 'possibly carcinogenic to humans' (Group 2B), based on limited evidence for one type of liver cancer. Group 2B describes how strong the evidence is that something could cause cancer under some circumstances — not how likely it is to cause cancer at normal intakes. The Joint FAO/WHO Expert Committee on Food Additives then reviewed the same evidence and kept the acceptable daily intake at 40 mg per kg of bodyweight. The WHO's own example: an adult weighing 70 kg would need to drink more than 9–14 cans of diet soft drink a day to exceed it.
The study that drew most attention was a French cohort of 102,865 adults (NutriNet-Santé, 2022): people with the highest sweetener intakes had a 13 percent higher rate of cancer than people who consumed none. That is an observational link, not proof — people who drink a lot of diet drinks often differ in other ways — but it is one reason not to treat sweeteners as a free pass.
Do diet drinks help you lose weight?
| Swap | Effect on body weight |
|---|---|
| Sugary drink → diet drink | About 1.06 kg less weight, lower BMI and body fat |
| Sugary drink → water | No clear effect in the trials available (only 3 trials) |
| Water → diet drink | No difference — diet drinks did not cause weight gain |
So for someone who drinks Coke or Pepsi daily, switching to the diet version is a genuine improvement. The WHO's 2023 guideline makes a different point: across longer studies, using sweeteners did not reduce body fat in the long run, so it advises against relying on them for weight control. A 2019 BMJ review of 56 studies reached a similar conclusion — for most health outcomes there was no clear difference between people who used sweeteners and those who did not. Both statements fit together: sweeteners help when they replace sugar, but they are not a weight-loss tool in themselves.
Sweetener or sugar in your tea?
Two teaspoons of sugar in each of four cups of tea a day is about 130 kcal and 32 g of sugar — more than half the WHO's suggested daily limit for free sugars, before any mithai. Replacing that with a sweetener tablet cuts those calories and sugar to almost nothing, which matters for weight, teeth and blood sugar. If you have diabetes, a sweetener is a far better choice than sugar. The best long-term option is to reduce sweetness gradually — half a spoon less each week — until plain or lightly sweetened tea tastes normal. Our sugar guide shows how.
Are some sweeteners better than others?
| Sweetener | Where you find it | What the evidence says |
|---|---|---|
| Aspartame | Diet colas, many sweetener tablets | IARC 'possible' (2B), safe limit unchanged; must be avoided with phenylketonuria (PKU) |
| Sucralose | Splenda, many 'sugar-free' products | Changed blood sugar responses in some people in a 2-week trial (Suez 2022) |
| Saccharin | Older sweetener tablets | Also changed blood sugar responses in some people in the same trial |
| Stevia | 'Natural' sweetener drops and sachets | No group-level change in blood sugar response in that trial |
| Erythritol | 'Keto' snacks, some stevia blends | Linked with heart attacks and strokes in observational data; increased clotting in lab tests (2023) |
The 2022 trial in the journal Cell gave 120 healthy adults small daily doses of saccharin, sucralose, aspartame or stevia for two weeks. All four changed gut bacteria, and saccharin and sucralose also worsened blood sugar responses at a group level, with large differences between individuals. The 2023 erythritol study in Nature Medicine found people with the highest blood erythritol levels had more heart attacks and strokes over three years, and erythritol made platelets clump more easily in the lab. Neither proves harm at normal intakes, but if you have heart disease or diabetes, there is no reason to choose erythritol-heavy products.
A simple way to decide
- Drinking sugary soft drinks or packaged juice every day? Switching to diet versions is a clear improvement; switching to water is better still.
- Taking sugar in tea several times a day? A sweetener is better than sugar; gradually less sweetness is best.
- Already drinking water and using little sugar? There is no reason to add sweeteners.
- Have diabetes? Sweeteners are a useful replacement for sugar; ask your doctor if you use a lot of sweetened products.
- Children: water and milk first. Sweetened drinks of either kind keep the taste for sweetness high.
This article is general information, not medical advice. People with phenylketonuria must avoid aspartame. If you have diabetes, kidney disease or heart disease, discuss sweeteners and sugar with your doctor or dietitian.
Frequently Asked Questions
Is aspartame safe to drink every day?
In normal amounts, yes. The WHO's food additives committee kept the safe limit at 40 mg per kg of bodyweight a day after its 2023 review; a 70 kg adult would need more than 9–14 cans of diet drink a day to exceed it. People with phenylketonuria must avoid aspartame.
Does aspartame cause cancer?
There is no proof that it does at normal intakes. In 2023 the WHO's cancer agency classed it as 'possibly carcinogenic' based on limited evidence, which describes uncertain evidence, not a measured risk. The safe daily limit was not changed.
Is Diet Coke better than regular Coke for weight loss?
Yes, if it replaces the regular version. In a 2022 meta-analysis of 17 trials, swapping sugary drinks for diet drinks reduced weight by about 1 kg. Water is just as good as a diet drink and has no sweetener at all.
Is sweetener better than sugar in tea?
For weight, teeth and blood sugar, yes. Two spoons of sugar in four cups a day adds about 130 kcal and 32 g of sugar. The best long-term option is gradually reducing sweetness until lightly sweetened tea tastes normal.
Which sweetener is the safest?
No sweetener has been shown to be harmful at normal intakes. Stevia and aspartame did not change blood sugar responses at a group level in a 2022 trial, while saccharin and sucralose did in some people. Erythritol is worth avoiding if you have heart disease, based on 2023 observational and lab findings.
Can people with diabetes use artificial sweeteners?
Yes. Using a sweetener instead of sugar avoids the rise in blood sugar that sugar causes. Water and unsweetened drinks are still the best everyday choice, and your doctor can advise if you use large amounts.
Sources
- World Health Organization. Aspartame hazard and risk assessment results released (IARC and JECFA), 14 July 2023
- Riboli E et al. Carcinogenicity of aspartame, methyleugenol, and isoeugenol. The Lancet Oncology, 2023
- Debras C et al. Artificial sweeteners and cancer risk: results from the NutriNet-Santé population-based cohort study. PLOS Medicine, 2022
- McGlynn ND et al. Association of low- and no-calorie sweetened beverages as a replacement for sugar-sweetened beverages with body weight and cardiometabolic risk: a systematic review and meta-analysis. JAMA Network Open, 2022
- World Health Organization. WHO advises not to use non-sugar sweeteners for weight control in newly released guideline, 15 May 2023
- Toews I et al. Association between intake of non-sugar sweeteners and health outcomes: systematic review and meta-analyses. BMJ, 2019
- Suez J et al. Personalized microbiome-driven effects of non-nutritive sweeteners on human glucose tolerance. Cell, 2022
- Witkowski M et al. The artificial sweetener erythritol and cardiovascular event risk. Nature Medicine, 2023
More guides
- How Much Sugar a Day Is Too Much? Tea, Mithai, Rooh Afza and the WHO LimitMost Pakistani adults eat double the sugar limit without touching a dessert — it is in the tea. Here is the WHO number, what the trials say sugar does to weight, a table of sugar in everyday desi food and drink, and the three cuts that matter.
- Fatty Liver (MASLD): The Diet and Exercise Plan That Reverses It — With Pakistani FoodThe ultrasound report says 'fatty liver, grade 1' and the doctor says 'lose weight'. Here is what fatty liver actually is, how much weight loss reverses it, why exercise helps even before the scale moves, a desi eating plan, and the tests worth asking about.
- Prediabetes and Insulin Resistance: The Warning Signs, What Your HbA1c Means, and How to Reverse ItAn HbA1c of 6.0, a 'borderline sugar' result, or a dark velvety patch on the back of the neck: prediabetes is the warning before type 2 diabetes, and in Pakistan it is extremely common. Here is what the numbers mean, the signs of insulin resistance, what the big prevention trials achieved — including one in South Asians — and a desi plan to bring your sugar back to normal.