Additives and ingredients to avoid

Humectant · Prohibited in cat food by the US FDA · 21 CFR 589.1001

Used to keep semi-moist foods soft and chewy. In controlled studies it caused Heinz body formation and shortened red blood cell survival in cats (a haemolytic anaemia) at doses that did not affect other species. The FDA specifically prohibited it in cat food as a result; it remains legal in dog food.

Why cats specifically

Feline haemoglobin has eight reactive sulfhydryl groups against two to four in most mammals, making cat red cells unusually vulnerable to oxidative damage. This same quirk underlies the onion, garlic, and paracetamol toxicities.

Where you might still meet it

Dog treats shared with a cat, and some imported or poorly regulated products. Read treat labels, not just food labels.

Synthetic antioxidant preservative · Originally registered as a pesticide · Banned in the EU and Australia for pet food

Very effective at preventing fat oxidation, which is why it persists. It is approved by the FDA for pet food at up to 75 ppm, but the EU withdrew its authorisation and Australia has restricted it. The published toxicology is genuinely inconclusive: concerns centre on liver enzyme changes and haemoglobin effects, and the EU withdrawal cited insufficient data to complete the safety assessment rather than a demonstrated harm.

The labelling trap

Ethoxyquin is often added to fish meal at the supplier stage, as a legally required stabiliser for shipping. Because the pet food manufacturer did not add it, it may not appear on the ingredient list at all. A food containing fish meal may contain ethoxyquin without saying so.

What to do

If it matters to you, ask the manufacturer directly whether their fish meal is ethoxyquin-free. Brands that use naturally preserved fish meal generally say so.

Synthetic antioxidant · IARC Group 2B, possibly carcinogenic to humans · No safe feline dose established by EFSA

BHA produced forestomach tumours in rats and hamsters at high doses, which is the basis for the IARC Group 2B classification and for California's Proposition 65 listing. Regulators generally hold that at permitted levels it presents no concern for consumer safety, but the EFSA opinion on BHA as a feed additive concluded that for cats a safe dose could not be established from the tolerance data available. Additional concerns raised in the literature include endocrine disruption and liver and kidney effects.

The practical point is that BHA is entirely avoidable. Mixed tocopherols and rosemary extract do the same job; they simply give a shorter shelf life, which is a cost to the manufacturer rather than to your cat.

Synthetic antioxidant · Frequently used alongside BHA

Shares BHA's profile: effective, cheap, long-standing consumer-advocacy concern over carcinogenicity, endocrine disruption, and liver injury, and the same gap in species-specific feline tolerance data. Assessed as safe at permitted levels by regulators, avoidable in practice.

Azo and triarylmethane dyes · Zero nutritional function

Cats have dichromatic vision and choose food by smell and texture. Colour exists solely so the product looks like meat chunks or “varied kibble” to the person paying. That matters because it means the risk-benefit calculation has a zero on the benefit side: any level of uncertainty is uncompensated.

The specific signals are modest but real, Red 40 and Yellow 5 carry contamination limits for benzidine and other aromatic amines; Yellow 5 (tartrazine) is associated with hypersensitivity reactions in a small subset of people; Blue 2 has been associated with tumour findings in some rodent studies. None of this is established in cats. But there is no reason to accept it.

Whitening pigment · Banned as a food additive in the EU since 2022

EFSA concluded in 2021 that titanium dioxide could no longer be considered safe as a food additive, because genotoxicity could not be ruled out for the nanoparticle fraction. The EU ban followed. It is still permitted in US pet food, where it appears in white or pale “gravy” and “cream” products for visual effect only.

Synthetic vitamin K precursor · Banned from human supplements in the US

The FDA prohibits menadione in human over-the-counter supplements because high parenteral doses caused haemolysis, hyperbilirubinaemia, and liver toxicity. It remains permitted in animal feed and turns up in pet food as a cheap vitamin K source. Cats rarely need supplemental vitamin K at all: AAFCO only requires it when the diet is more than 25 % fish, because gut bacteria supply the rest. Natural phylloquinone (K1) is available and is what better formulations use.

Curing salt · Distinct from its legitimate use as an antibotulinal in some products

Used in some semi-moist and treat products to keep a red, meaty appearance. Two concerns: at high intake it can cause methaemoglobinaemia, and under heat it can form nitrosamines with secondary amines in meat. Cats' oxidatively fragile haemoglobin makes the first concern more relevant than it would be in other species. Where a food needs no colour fixative, it should not have one.

Seaweed-derived thickener and stabiliser · Genuinely contested

The most argued-about ingredient in wet cat food, and the one where it is most important to be precise. Two forms exist. Degraded carrageenan (poligeenan) is a recognised intestinal inflammatory agent used deliberately to induce colitis in laboratory animal models, but it is not a permitted food ingredient. Undegraded, food-grade carrageenan is what is actually in pet food, and its safety is contested rather than settled: JECFA and EFSA have repeatedly concluded it is acceptable at food-use levels, while some researchers argue that partial degradation occurs in the acidic stomach and during processing, and that low-grade intestinal inflammation results.

Honest summary

There is no good evidence of harm to cats at the levels used. There is also no nutritional benefit: it is a texture ingredient. Given cats eat the same formulation every day for a decade or more, and given that guar gum, xanthan gum, cassia, and locust bean gum do the same job, avoiding it is a low-cost precaution rather than a scientific necessity.

When it matters more

Cats with inflammatory bowel disease, chronic diarrhoea, or food-responsive enteropathy. In that population it is worth eliminating as a trial.

Thickeners and gelling agents · Generally well tolerated

The usual carrageenan substitutes. No meaningful safety signal, but they are fermentable and in quantity can loosen stools in sensitive cats. If a cat develops diarrhoea after switching to a gravy- or jelly-style product, the gum system is a reasonable suspect. Pâté formats usually use less.

Palatants · Extremely effective; poorly disclosed

Cats respond strongly to free amino acids, so hydrolysates and glutamate-rich extracts are powerful palatants. There is no established toxicity in cats at food levels. The problem is different: they work too well. A heavily palatant-coated food can drive overeating in a species that is already the most obesity-prone pet in the developed world, and it can make a cat unwilling to accept a plainer therapeutic diet later. “Animal digest” also does not name a species.

Humectants, palatants, and colour · Nutritionally pointless in cats

Cats cannot taste sweetness (the sweet-receptor gene is a pseudogene) so sugar is not there for the cat's benefit. It softens semi-moist products, browns them appealingly, and adds empty calories to an animal predisposed to obesity and diabetes. There is no argument for it.

Synthetic antioxidants · Less studied than BHA and BHT

Alternative synthetic antioxidants that appear when a manufacturer avoids BHA and BHT but still wants a long shelf life. Both are permitted; both have thinner safety datasets than the compounds they replace, and neither has meaningful feline-specific data. Natural alternatives exist.

Emulsifiers, acidulants, and tartar-control agents · Relevant to kidney health

Not toxic, but they raise dietary phosphorus in its most rapidly absorbed form. High phosphorus intake (particularly from inorganic salts rather than from bone and meat) is associated with kidney injury in cats, and phosphorus restriction is the single best-evidenced dietary intervention in chronic kidney disease. For a healthy young cat this is a minor point; for a senior cat, or any cat with even early CKD, it is worth attention.

Flavouring · Should not be in cat food at all

Occasionally found in low-quality treats, table-food-styled products, and broths marketed as toppers. The organosulfur compounds in Allium species cause oxidative damage to feline red blood cells and Heinz body anaemia; cats are more sensitive than dogs. The amounts in a flavouring are usually small, but the effect is cumulative and there is no reason to accept any. More on Allium toxicity →

“Chicken by-product meal”, “turkey by-products”

By-products are the non-skeletal-muscle parts of the animal: liver, heart, kidney, spleen, lung. These are not waste; they are the organs a wild cat eats first, and heart is the best natural taurine source available. AAFCO's definition specifically excludes hair, horn, teeth, and hooves. The legitimate criticism is about unnamed by-products, where you cannot verify the species or the batch-to-batch consistency, not about by-products as a category.

“Chicken meal”, “salmon meal”, “lamb meal”

Rendered and water-removed, so protein-dense by weight. A named meal high in an ingredient list is a genuinely good sign; it reflects real contribution to the finished food rather than the pre-cooking water weight of fresh meat. Unnamed meals are the ones to question.

Natural preservatives

These are the alternatives to BHA, BHT, and ethoxyquin, and there is no safety concern with them. The trade-off is a shorter shelf life, which is why you should buy bag sizes you will finish within about six weeks. The occasional claim that rosemary extract triggers seizures in epileptic pets is not supported by evidence.

“Taurine” in the ingredient list

Should be there. Processing and storage degrade taurine, canned diets lose more of it, and deficiency causes irreversible blindness and heart failure. Seeing supplemental taurine on a label is a mark of a formulation that understands cats: not a sign that the food is deficient in real meat.

Fibre sources

Beet pulp in particular is often attacked as “filler”. It is a moderately fermentable fibre that supports stool quality and colonic health, and it contains negligible sugar. Fibre is not an essential nutrient for cats but it is functionally useful for constipation, hairballs, and satiety in weight-loss diets.

The long chemical-sounding tail of any ingredient list

“Thiamine mononitrate”, “pyridoxine hydrochloride”, “zinc proteinate”, “sodium selenite”, these are the vitamins and minerals from the AAFCO profile, in the forms that survive processing and are absorbed. Their presence is what makes a food complete. Chelated (“proteinated”, “amino acid complex”) minerals are generally better absorbed than inorganic sulfates and oxides.