Saccharin vs Yellow Dye 5: which is worse?

What is Saccharin?

Saccharin is the oldest artificial sweetener, discovered accidentally at Johns Hopkins in 1879. It is a sulfonamide compound approximately 300-400 times sweeter than sucrose with no caloric value. It has a slightly bitter metallic aftertaste at higher concentrations. Saccharin's sodium salt (sodium saccharin) is the form used in most food applications.

What is Yellow Dye 5?

Yellow Dye 5 (tartrazine) is a synthetic lemon-yellow azo dye derived from petroleum. It produces a bright, stable yellow color in acidic conditions and is one of the most widely used yellow dyes globally. Its chemical formula is C16H9N4Na3O9S2.

Documented risks

Saccharin: Saccharin's carcinogenicity history is one of the most tumultuous in food regulatory history. In 1977, the FDA proposed banning saccharin after studies found it caused bladder cancer in rats at very high doses. Congress passed the Saccharin Study and Labeling Act, which put a moratorium on the ban and required a cancer warning label on saccharin products ('Use of this product may be hazardous to your health. This product contains saccharin which has been determined to cause cancer in laboratory animals.'). By 2000, saccharin was removed from the US National Toxicology Program's Report on Carcinogens after subsequent research determined that the bladder cancer in male rats was caused by a rat-specific mechanism — high pH, high protein, and calcium phosphate in rat urine — that does not apply to human urine. The cancer warning label requirement was repealed. IARC also removed saccharin from its Group 2B list in 1999. However, Canada maintained its ban on food use saccharin, citing continued precautionary concern. A 2022 study in Cell found saccharin was among the artificial sweeteners most significantly altering gut microbiome composition and glucose tolerance in previously non-sweetener-using participants. Saccharin showed the largest effect on glucose tolerance among the sweeteners studied (saccharin, sucralose, aspartame, stevia). Saccharin passes through the placenta and appears in breast milk, raising questions about infant exposure that have not been fully resolved.

Yellow Dye 5: Yellow Dye 5 was one of six dyes studied in the landmark 2007 McCann et al. study in The Lancet. The study found statistically significant increases in hyperactivity in children ages 3 and 8–9 given a mixture containing tartrazine and sodium benzoate. EFSA reviewed the evidence and confirmed the effect was real, mandating the EU warning label from 2010. A 2012 review in Neurotherapeutics (Arnold et al.) confirmed that artificial food colors including tartrazine have a small but statistically significant adverse effect on children's behavior that is not confined to those with diagnosed ADHD. Tartrazine is one of the most documented causes of food dye hypersensitivity. Cross-reactivity with aspirin (acetylsalicylic acid, ASA) is well established in allergy literature: individuals with aspirin hypersensitivity have elevated risk of reacting to tartrazine. Symptoms include urticaria, angioedema, rhinitis, and in rare cases anaphylaxis. Prevalence of tartrazine sensitivity is estimated at 0.1% of the population but higher in aspirin-sensitive individuals. Because of this known hypersensitivity risk, the FDA specifically requires Yellow No. 5 to be declared by name on US food labels — an exceptional requirement not applied to most other additives, reflecting the FDA's acknowledgment of this real clinical concern. EFSA's 2009 re-evaluation found no evidence of genotoxicity in standard test systems at food use levels, setting an ADI of 7.5 mg/kg body weight, but noted in vitro evidence at higher doses. In April 2025, the FDA announced plans to phase out Yellow 5 along with other petroleum-based dyes.