E951 Aspartame

E951SweetenersOrigin: Lab-made

Get a personal answer

Pick your family’s diets in the bar above.

Every diet

VeganYes

Amino acids made by fermentation.

Gluten-freeYes

HalalYes

KosherYes

KetoYes

Low-FODMAPYes

The short answer

Aspartame (E951) is a zero-calorie sweetener in diet soda. It's approved, but WHO's cancer agency called it "possibly carcinogenic" in 2023, and people with PKU must avoid it.

55/100

Use in moderation

Safe in small amounts; may bother some people or raise blood sugar.

E-numberE951

Comes fromLab-made

What it doesSweeteners

Glycemic index0

Daily limit40 mg/kg

Also calledAspartame, NutraSweet

Rules by country

🇺🇸 US FDAApproved with limits

🇪🇺 European UnionWarning label required

🇨🇦 Health CanadaApproved with limits

CaliforniaNo extra rules

Approved everywhere. Labels must warn people with phenylketonuria (PKU) because it contains phenylalanine. In 2023 the WHO's cancer agency classed it as "possibly carcinogenic" (2B) while JECFA kept its 40 mg/kg limit.

How much is too much? (Acceptable Daily Intake)

Body weight: 70 kg

2.8 gper day is the safe upper limit

Based on 40 mg per kg of body weight (EFSA / JECFA). A 20 kg (44 lb) child: 800 mg a day.

What is it?

Aspartame is about 200 times sweeter than sugar. It breaks down in heat, so it's used in drinks, not baking.

Where it comes from: Made by joining two amino acids, aspartic acid and phenylalanine, usually produced by fermentation.

Why it’s in food

Sweetens diet sodas and gum
Replaces sugar in yogurt and desserts

Often found in

Diet sodaSugar-free gumLight yogurtTabletop sweeteners

Also listed as: Aspartame, NutraSweet, Equal, APM

Health & gut impact

Cancer classificationUnder study

IARC classified it as possibly carcinogenic (2B), based on limited evidence.

IARC Monographs Vol. 134 (2023)

PKUUnder study

Dangerous for people with phenylketonuria.

FDA 21 CFR 172.804

Daily limitConcern

A 70 kg adult would need over 9 cans of diet soda daily to reach the limit.

JECFA (2023)

What can I use instead?

Stevia

Ratio: Follow package

Best for: Drinks

Aspartame vs Sucralose

More sweeteners:

AlluloseAllulose is a "rare sugar" that tastes like sugar but has almost no calories and doesn't raise blood sugar. It's keto-friendly and browns like real sugar in baking.Generally safe Erythritol E968Erythritol (E968) is a zero-calorie sugar alcohol popular in keto foods. A 2023 study linked high blood levels to heart risk, and large amounts can upset your stomach.Use in moderation High-Fructose Corn Syrup (HFCS)High-fructose corn syrup is a liquid sugar made from corn. It's vegan and gluten-free, but it's sugar: not keto, not low-FODMAP, and best limited.Use in moderation Monk Fruit Extract (Luo Han Guo)Monk fruit is a zero-calorie sweetener from a Chinese melon. It's vegan and keto-friendly, but most store blends are mostly erythritol.Generally safe

Common questions

Is Aspartame safe?

Use in moderation (55/100). Approved everywhere. Labels must warn people with phenylketonuria (PKU) because it contains phenylalanine. In 2023 the WHO's cancer agency classed it as "possibly carcinogenic" (2B) while JECFA kept its 40 mg/kg limit.

Is Aspartame vegan?

Yes. Amino acids made by fermentation.

Is Aspartame gluten-free?

Yes.

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Scientific sources & regulatory citations

21 CFR 172.804 (US FDA)
EFSA OpenFoodTox: E951
IARC Monographs Vol. 134 (2023)
FDA 21 CFR 172.804
JECFA (2023)

Last checked against FDA, EFSA and Health Canada records: October 31, 2026 · INS 951 · CAS 22839-47-0