Aspartame (sold as NutraSweet and Equal) is a non-nutritive sweetener about 200 times sweeter than sugar. It's made from two amino acids — aspartic acid and phenylalanine — and unlike sucralose it breaks down under high heat, so it's used mostly in cold products: diet sodas, sugar-free gum, "light" yogurts, powdered drink mixes, and some sugar-free puddings and gelatins. The FDA approved aspartame in 1981 and has reaffirmed its safety in multiple reviews; the FDA Acceptable Daily Intake is 50 mg/kg of body weight.
The 2023 news that put aspartame back in the headlines: the World Health Organization's cancer agency (IARC) classified aspartame as "possibly carcinogenic to humans" (Group 2B) in July 2023. It's important to read that classification carefully — Group 2B is a low-certainty category that also includes aloe vera extract and pickled vegetables, and it reflects "limited evidence." At the same time, the WHO/FAO joint expert committee (JECFA) reviewed the same evidence and kept the Acceptable Daily Intake at 40 mg/kg, meaning a person would need to drink a large number of diet sodas daily to approach the limit. The FDA publicly disagreed with the IARC classification.
For kids, the relevant guidance is the AAP 2019 policy statement on non-nutritive sweeteners, which applies to aspartame along with sucralose: data on long-term effects in children is limited, and there's concern that early exposure to intense sweetness may shape taste preferences. Aspartame also carries a hard rule for one group — children with phenylketonuria (PKU) must avoid it because they can't metabolize phenylalanine, which is why US labels state "Phenylketonurics: Contains Phenylalanine." For everyone else, the practical lens is moderation and preferring whole-food-sweetened snacks.
How to spot it on a label: "Aspartame," "NutraSweet," "Equal," or the mandatory PKU warning "Contains Phenylalanine." It's most common in diet soda, sugar-free gum and mints, "light"/"diet" yogurts, and powdered drink mixes. If you'd rather avoid all non-nutritive sweeteners for your child, prefer products sweetened by fruit or dates; if you're choosing between sweeteners, the FDA and EFSA give sucralose a wider safety margin than aspartame.