E food additives

E951 – Aspartame

Orange grain dots symbol for food additive with some concerns (E number classification – ORANGE level).

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Safety grading ORANGE – SOME CONCERNS

Why ORANGE? Aspartame (E951) is legally permitted in both the EU and the US as a high-intensity sweetener, with long-standing evaluations finding it safe at current exposure levels. In July 2023, the WHO’s International Agency for Research on Cancer (IARC) classified aspartame as “possibly carcinogenic to humans (Group 2B)” based on limited human evidence (mainly liver cancer signals from observational studies). Importantly, on the same day the WHO/FAO Joint Expert Committee on Food Additives (JECFA) reaffirmed the existing Acceptable Daily Intake (ADI) of 0–40 mg/kg body weight/day, concluding the overall evidence for harm at ordinary intakes is not convincing. Regulators including the US FDA continue to authorise its use within established limits.

This mixed picture – regulatory agencies keeping current ADIs while IARC flags a potential hazard – places aspartame in a cautionary middle ground rather than “unsafe.” For most consumers, typical intakes from diet beverages, sugar-free gums and tabletop sachets are well below the ADI. However, sensitive or high-intake groups (e.g., heavy diet-soda consumers) should monitor cumulative consumption. A critical exception is people with phenylketonuria (PKU), who must avoid aspartame because it provides phenylalanine. Considering the legal status, ADI reaffirmations and ongoing debate, an ORANGE grade accurately reflects some concerns (hazard signal + controversy) without overstating risk at normal use levels.

Should You Avoid Aspartame?

Generally, no if you’re a healthy adult staying within the ADI. If you prefer to minimise controversial ingredients, choose alternatives like stevia or sucralose. Do avoid aspartame if you have PKU (always check labels for “contains a source of phenylalanine”). Pregnant individuals or those with specific medical advice may choose moderation or alternatives out of caution.

Common Uses

  • Diet/zero-sugar soft drinks and energy drinks (intense sweetness with very few calories)
  • Sugar-free chewing gums and candies
  • Tabletop sweetener sachets and tablets
  • Low-calorie yoghurts, desserts, and gelatin mixes
  • Pharmaceuticals (e.g., flavoured lozenges) and some oral care products

Common names / Synonyms

  • Aspartame
  • INS 951 / E951
  • Brand/trade names: NutraSweet®, Equal®, Canderel®
  • Often blended as Aspartame-Acesulfame Salt (INS 962; “Twinsweet”)

What is Aspartame?

Aspartame is a low-calorie, high-intensity sweetener about 200× sweeter than sucrose. Chemically, it is the methyl ester of a dipeptide composed of the amino acids L-aspartic acid and L-phenylalanine. Because the required amount to sweeten foods is tiny, the caloric contribution is negligible at use levels, even though gram-for-gram it contains ~4 kcal like other amino-acid-based substances.

How it’s made: Industrial production typically starts from the two amino acids, which are protected and coupled to form the dipeptide, then esterified (methylated) and purified to yield crystalline aspartame. Manufacturers control stereochemistry so the product is the sweet-tasting L-isomer combination. Quality steps remove residual reagents and by-products.

In products & stability: Aspartame’s clean sweetness profile makes it popular in beverages and tabletop sachets, often blended with other sweeteners (e.g., acesulfame-K) to improve taste and stability. It is not heat-stable at high temperatures or prolonged heating and can hydrolyse in water, which is why it’s less ideal for baking or long hot-hold applications compared with sucralose or acesulfame-K. In the body, aspartame is metabolised to its components – aspartic acid, phenylalanine, and a small amount of methanol – at levels substantially below those found in many common foods when consumed within the ADI.

Safety landscape: Multiple bodies have reviewed aspartame for decades. In 2023, IARC classified it as possibly carcinogenic (Group 2B), a hazard label that does not account for typical intakes. In parallel, JECFA and major regulators maintained existing ADIs (EU: 0–40 mg/kg bw/day; US: 0–50 mg/kg bw/day) based on overall evidence that does not demonstrate risk at permitted levels. This is why regulators continue to authorise it while advising consumers to stay within intake limits and PKU individuals to avoid it entirely.

Where it’s allowed (EU vs US)

EU: Authorised as food additive E951 with an ADI of 40 mg/kg bw/day and mandatory labelling (name or E-number).

US: FDA approves aspartame as a food additive; ADI effectively 50 mg/kg bw/day. Both jurisdictions continue to allow use within established conditions.

Further reading

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