A class action lawsuit against Mars Petcare US Inc. is challenging labeling on Nutro Natural Choice dog food, alleging the products are falsely marketed as containing “No Artificial Flavors, Colors, or Preservatives” despite including ingredients the plaintiff claims function as synthetic preservatives.
Filed April 6, 2026, in the U.S. District Court for the Southern District of California, the complaint Flick v. Mars Petcare US Inc. centers on the use of citric acid and mixed tocopherols in the formulations. The plaintiff alleges both ingredients qualify as “chemical preservatives” and contradict the front-of-pack claim.
According to the filing, the Nutro products’ packaging prominently states they contain no artificial preservatives, while the ingredient panel lists both citric acid and mixed tocopherols. The plaintiff argues these substances are used to “prevent or retard deterioration,” aligning with the U.S. Food and Drug Administration’s definition of a chemical preservative.
The lawsuit contends that although citric acid can be derived naturally, nearly all commercially used citric acid is produced through industrial fermentation processes involving Aspergillus niger. This manufacturing method, the plaintiff alleges, makes the ingredient synthetic from a consumer perception standpoint.
Similarly, the complaint asserts that the tocopherols used in pet food are typically synthetic forms derived from petrochemical sources and are primarily included to extend shelf life by preventing fat oxidation.
Fact check: ingredient use and function
On citric acid, the plaintiff’s description of the industrial process is broadly accurate, but the interpretation is arguable. Commercial citric acid production is dominated by fermentation using Aspergillus niger. However, regulatory frameworks do not uniformly classify fermentation-derived citric acid as “synthetic,” and it is widely used in both human and pet foods without automatically disqualifying “natural” claims. If Aspergillus fermentation products were to be considered synthetic, it could open a wide range of other ingredients to further lawsuits.
Many ingredients in human and pet food are produced through microbial fermentation, similar to citric acid, including organic acids like lactic and propionic acid, amino acids such as lysine and threonine, and vitamins like B2 and B12. Fermentation is also widely used to produce enzymes, hydrocolloids like xanthan gum, and flavor ingredients such as yeast extracts and monosodium glutamate, making it a foundational process in modern food systems. Although these ingredients are often chemically identical to naturally occurring compounds, their production method plays a central role in ongoing debates over labeling terms like “natural” and “no artificial preservatives.”
For tocopherols, the lawsuit’s characterization is even more nuanced. The ingredient panel shown in the complaint explicitly lists “mixed tocopherols (preservative),” confirming the products do use tocopherols for oxidative stability. Their functional role as antioxidants that prevent fat rancidity is well established in pet food formulation. That claim was accurate.
However, the claim that tocopherols used in pet food are “typically synthetic” is not consistently supported. Mixed tocopherols used in pet food are commonly derived from plant oils and are often positioned by manufacturers as natural-source antioxidants. Synthetic forms of vitamin E do exist and are used in some applications, but they aren’t as prevalent as mixed natural tocopherols.
Similar lawsuits related to pet food labeling
The distinction between “natural,” “synthetic,” and “preservative” remains a persistent target for lawsuits over pet food labeling.
Unlike earlier cases, including 2023 litigation involving Nestlé Purina’s natural-claims, that broadly challenge the use of the term “natural,” the Nutro lawsuit focuses on a narrower and more specific claim: the absence of artificial preservatives.
Previous lawsuits often argued that “natural with added vitamins and minerals” misleads consumers despite qualifying language. Courts have frequently treated those disputes as questions of consumer interpretation. By contrast, the Nutro case may hinge more directly on whether specific ingredients qualify as artificial preservatives under regulatory and consumer standards.
That distinction could prove significant. A claim about the absence of artificial preservatives may be easier to test against ingredient function and classification than the broader, more subjective meaning of “natural.” Still, the underlying issue remains the same: how consumers interpret ingredient sourcing and processing versus how regulators and manufacturers define those terms.
The Nutro case underscores that dynamic, suggesting that even as “natural” and “no artificial” claims face scrutiny, more specific clean-label statements may increasingly become the focus of future lawsuits.
