Aspartame

What is aspartame?

Aspartame is a low-calorie artificial sweetener made from two natural amino acids — L-aspartic acid and L-phenylalanine — bonded to a methyl ester. It is roughly 200 times sweeter than sucrose, provides 4 kcal per gram (like any protein), but is used in such small amounts that its calorie contribution to food is negligible.

Aspartame carries E-number E951 in the EU. It was discovered accidentally by chemist James Schlatter at G.D. Searle in 1965, approved by the FDA for dry-goods use in 1981, expanded to beverages in 1983, and approved for general use in 1996. It is one of the most extensively tested food additives in the regulatory record.

What foods and drinks contain aspartame?

• Diet carbonated soft drinks — Diet Coke, Diet Pepsi, Coca-Cola Zero (historically; now blended with acesulfame-K).
• Sugar-free chewing gum — Extra, Trident, Orbit.
• Sugar-free flavoured yoghurts.
• Tabletop sweeteners — Equal, NutraSweet, Canderel.
• Sugar-free jellies, puddings, and desserts.
• Protein shakes and meal replacements, especially "diet" and low-carb variants.
• Cough syrups and chewable vitamins — non-food use.

Aspartame is not heat stable and cannot be used in baked goods that reach high temperatures without losing sweetness. This is why sugar-free baked goods typically use sucralose or acesulfame-K instead.

What is the current regulatory position on aspartame?

The FDA, EFSA, JECFA, and Health Canada all currently classify aspartame as safe at intakes up to the ADI. Two ADIs are in use: 40 mg/kg body weight per day (EFSA and JECFA) and 50 mg/kg body weight per day (FDA). The IARC classified aspartame as Group 2B — 'possibly carcinogenic to humans' — in July 2023.

The IARC and JECFA reviews were conducted in parallel and released jointly. The IARC classification was based on limited evidence for hepatocellular carcinoma in three observational cohorts, limited evidence in one animal study, and limited mechanistic evidence. JECFA, evaluating the same body of literature under a risk-assessment framework, concluded that the ADI did not need to change because the observational evidence was insufficient to demonstrate causation and the animal data were not consistent enough to define a lower NOAEL.

The distinction between hazard and risk is central. Group 2B (IARC) means "there is some evidence the substance can cause cancer in some circumstances" — the same category as gasoline exhaust, aloe vera whole-leaf extract, and pickled Asian vegetables. It does not mean typical dietary exposure is dangerous. NakedCalorie surfaces both the IARC classification and the current ADI on every aspartame-containing product.

What does the human evidence show?

The three cohort studies underlying the IARC 2B classification are the NutriNet-Santé (France), the NIH-AARP Diet and Health Study (US), and a smaller Italian cohort. Each reported a modest positive association between artificially sweetened beverage intake and one or more cancer endpoints, with confidence intervals that did not consistently exclude the null.

Debras et al. (PLoS Medicine, 2022) analysed 102,865 adults in NutriNet-Santé over a median 7.8 years and reported a hazard ratio of 1.13 (95% CI 1.03–1.25) for overall cancer risk in high consumers of artificial sweeteners, driven by aspartame and acesulfame-K. The NIH-AARP analysis reported similar-magnitude associations for hepatocellular carcinoma. Neither study can rule out confounding by the broader ultra-processed dietary pattern in which artificial sweeteners are consumed.

The 2023 WHO guideline on non-sugar sweeteners, based on a systematic review of 283 studies by Rios-Leyvraz and Montez, recommended against the use of non-sugar sweeteners for weight control and flagged possible long-term risks of type 2 diabetes and cardiovascular disease. The guideline covers the class, not aspartame specifically.

Is aspartame a NOVA Group 4 marker?

Yes. Aspartame is a non-sugar sweetener, and any cosmetic additive of that class triggers NOVA Group 4 classification under Monteiro 2019. A diet cola sweetened with aspartame is Group 4; the same beverage sweetened with sucrose is also Group 4 because of the caramel colour, phosphoric acid, and flavourings. The classification does not distinguish between sugar and sugar-substitute versions of the same industrial formulation.

How does NakedCalorie flag aspartame?

Aspartame is a Tier 2 evidence-linked additive in the encyclopedia, surfaced individually on every scan with the current IARC classification (2B) and the applicable ADI. Products carrying aspartame also carry the mandatory phenylalanine warning where required.

The score does not treat aspartame as unsafe — it reflects the regulatory position that the additive is permitted at current use levels — but it does surface the contested evidence base for users to consider. For related sweeteners see sucralose; for the class-level discussion of non-sugar sweeteners see the sweetener section on the additives hub.