Aspartame: what should you make of it?

We spot it every morning: that little white tablet dissolving in coffee without a second thought. Behind it is a name that keeps resurfacing in conversation: aspartame. This intense sweetener, about 200 times sweeter than sugar, has been authorised in Europe since the early 1980s. And ever since, the same question comes back: can we consume it without worry?

What we know

In Europe, the European Food Safety Authority (EFSA) has set an acceptable daily intake of 40 mg per kilo of body weight. In practice, for a 60 kg person, that means around ten cans of diet fizzy drink or about forty sweetener tablets a day — a truly unusual level of consumption.

In July 2023, two World Health Organization bodies published their conclusions. The International Agency for Research on Cancer (IARC) classified aspartame as 'possibly carcinogenic to humans' (Group 2B), a category that signals limited evidence, not an established danger. The JECFA expert committee maintained the acceptable daily intake at 40 mg/kg. In other words: no solid evidence of risk at usual doses, but reason to stay measured.

The only truly documented case remains phenylketonuria. This rare genetic condition prevents the body from processing phenylalanine, an amino acid found in aspartame. People affected must avoid it, and products containing it state this on the label. Outside this situation, current data have not identified harmful effects in the general population.

Unbranded cans of diet fizzy drink lined up on a light kitchen counter — The daily intake translated into cans: a reason to keep things in perspective

Aspartame and weight loss: the shortcut to avoid

Aspartame does not make you lose weight. Its presence in a drink alone does not trigger any weight loss. What it can do is replace sugar in certain products — fizzy drinks, yoghurts, chewing gum — and lighten the calorie total for the day.

Young woman in a bright kitchen, holding a glass of a diet drink with an open packet of biscuits on the table — Replacing sugar is not enough if snacking takes over again

Two caveats matter. If you compensate by snacking more, the calorie advantage disappears. And one question remains open: some research suggests that intense sweeteners may not be as satiating as sugar and could sustain a liking for sweet things. The data remain mixed and the debate continues. If you are unsure about your intake, speak to a healthcare professional.

What we know: moderate use stays within the acceptable daily intake set by EFSA. What we do not yet know: the effects of very high consumption over many years. Prudence here means moderation and variety — not prohibition.

In practice, remember this

A diet fizzy drink now and then is not a problem for a healthy person. Daily, heavy use, however, is a prompt to diversify: water, tea, herbal teas, flavoured waters with no added sugar. And if you are looking for an alternative to sweeten your coffee, stevia, which comes from a plant, contains no phenylalanine. You will find it in tablets or powder, often in a glass jar or sachets. Check the ingredients, as blends on the shelf sometimes add other ingredients.

Glass jar of stevia tablets, green powder and fresh leaves next to a cup of herbal tea — Stevia, a plant-based alternative without phenylalanine

Budget

A box of 100 to 300 sweetener tablets costs around £2 to £5 in the UK, depending on brand and format. Powder is usually about £3 to £6 a tub. A diet fizzy drink works out at about £1 to £2 per 1.5 litres, in supermarkets and online. Stevia-based alternatives cost a little more, often between £4 and £7 a box. These differences depend on format, brand and where you shop: supermarket, health food shop, pharmacy or online order.