Are diet drinks ultra-processed?

Yes. A diet soda has a sweetener like aspartame or sucralose, plus colors and flavors, and NOVA counts all three as markers of ultra-processed food. It adds almost no calories, and the 2025 to 2030 US guidelines still say to limit low-calorie sweeteners. Sparkling water is the swap.

People switch to diet soda to cut sugar, and that part works. A 12-ounce can of regular cola has about 37 g of sugar, and the diet one has none. That makes it feel like diet soda should be off the hook. NOVA doesn’t look at sugar at all. It looks at what’s in the can, and a sweetener is a cosmetic additive in its system.

We’d call diet over regular a real improvement, and sparkling water the finish line. If you drink several cans a day, move one of them at a time to sparkling water, plain or with a squeeze of lemon, and keep the fizz.

Diet soda is like decaf. It fixes the one thing you were trying to cut, and it’s still the same kind of drink.

Why it’s group 4

NOVA’s 2019 paper lists sweeteners, colors and flavors among the cosmetic additives that mark ultra-processed food, and its 2016 paper puts carbonated drinks first in its list of typical ultra-processed products. The same paper says even a plain yogurt with an artificial sweetener added belongs in group 4.

What the guidelines and the FDA say

The 2025 to 2030 Dietary Guidelines tell Americans to “avoid sugar-sweetened beverages, such as sodas, fruit drinks, and energy drinks”, and to “limit foods and beverages that include artificial flavors, petroleum-based dyes, artificial preservatives, and low-calorie non-nutritive sweeteners” (page 4).

The FDA approves each sweetener with an acceptable daily intake. A 132 lb person would need about 75 packets of aspartame a day to reach its limit. In 2023 the World Health Organization’s cancer agency called aspartame “possibly carcinogenic”. The FDA disagrees with that conclusion and has no safety concerns at approved uses.

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Why the share tools barely see it

From the site’s food table (USDA). The day’s share calculator measures the share of your calories that came from group 4, so a diet soda adds almost nothing to it. It says so on a line of its own when you pick one, since the can is still group 4.

What we’d do

• If you drink regular soda, switching to diet cuts the sugar right away.
• Then move one can a day to sparkling water, plain or with citrus.
• See the drink rung of the swap ladder.