Key findings
- 1Artificial sweeteners in diet soda are among the most chemically engineered molecules in any common food product
- 2Caramel color (Class IV) is produced through the ammonia-sulfite process, creating 4-methylimidazole, listed as a potential carcinogen under California's Proposition 65
- 3Sparkling water with real fruit juice provides carbonation and flavor with far less processing and no synthetic sweeteners
Why is Diet Soda ultra-processed on average?
Diet soda is often perceived as a healthier alternative to regular soda, but from a processing standpoint it is equally industrial. Aspartame is synthesized from phenylalanine and aspartic acid through bacterial fermentation and chemical coupling. Sucralose is made by chlorinating sugar molecules (replacing three hydroxyl groups with chlorine atoms). Acesulfame potassium (Ace-K) is a potassium salt produced through chemical synthesis. These artificial sweeteners are among the most heavily engineered molecules in the food supply. Caramel color in cola-type diet sodas is not simply "heated sugar"; it is produced through the ammonia-sulfite process (Class IV caramel), which creates 4-methylimidazole (4-MEI), a compound California lists under Proposition 65 as a potential carcinogen. Phosphoric acid, sodium benzoate (preservative), and proprietary "natural flavors" complete the manufactured formulation. In our analysis, diet soda averages a Processing Score of 8.7, which is Level 4.
How 426 diet soda products break down
Share of products at each processing level, in our analysis.
Diet Soda brand comparison
From least to most processed in our database.
How to read a diet soda label
- 1
Aspartame, sucralose, and acesulfame potassium are all synthesized chemicals, not natural sweeteners
- 2
Caramel color (in cola varieties) is Class IV caramel produced using ammonia; not simple heated sugar
- 3
Phosphoric acid provides the tart bite in cola, and it is industrially manufactured
- 4
Sodium benzoate (preservative) can form benzene when combined with ascorbic acid (vitamin C)
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Frequently asked questions
Is diet soda better than regular soda?
In our analysis, diet soda averages a Processing Score of 8.7, which is Level 4. Diet soda has zero calories, but it replaces one industrial ingredient (HFCS or sugar) with others (synthetic sweeteners). From a processing standpoint, neither is better. Sparkling water is the far less processed carbonated alternative.
What is caramel color really made from?
Class IV caramel color used in cola is not simple heated sugar. It is produced by reacting sugar with ammonia and sulfite compounds under high pressure, creating the brown coloring along with 4-methylimidazole (4-MEI), a byproduct that California lists as a potential carcinogen.
Are zero-calorie sodas less processed than diet soda?
No. "Zero sugar," "zero calorie," and "diet" sodas all use the same synthetic sweeteners and industrial ingredients. The different names are marketing distinctions, not processing differences.
Guide · Beverages
The Complete Beverages Guide
Processing analysis, least-processed picks, and what to watch for.
Read guide