ONE Purina Dog Food, Adult, With Real Salmon & Tuna 60.8 Oz

⚪ Formulation signal: corn gluten meal is a concentrated plant protein. It counts toward the crude protein figure on the guaranteed analysis without contributing meat — and since that figure doesn't distinguish sources, a food can advertise strong protein while much of it is plant-derived and lower in the amino acids dogs use most. That's a labelling limitation, not a toxicity claim. No canine harm has been shown at label levels.

⚪ Transparency signal: 'natural flavor' in pet food is most often animal digest — hydrolysed animal tissue sprayed on the outside of the kibble to make it palatable. It is not required to name the species. The concern is not toxicity, it is that a bag can list an unnamed animal product and disclose nothing about what it was.

⚪ Formulation signal: soybean meal is concentrated plant protein used to raise the crude protein number on the guaranteed analysis without meat. The protein percentage on a label does not distinguish source, so a food can advertise strong protein while much of it is plant-derived and lower in the amino acids dogs actually need. Soy is also a common allergen and usually a GMO, glyphosate-treated crop. Matters most in the top five.

Certain types of caramel color produced using ammonia processes may contain 4-methylimidazole (4-MEI), a compound that some research has associated with potential carcinogenic activity

⚪ Safe synthetic at label levels: pyridoxine HCl is synthetic vitamin B6, and it's the standard, effective form used across pet food. Dogs require B6 for protein metabolism and neurotransmitter production, and deficiency causes anaemia and seizures. The reason for noting it at all is that B6 has an unusually narrow window at the top end for a B vitamin: chronic excess causes peripheral neuropathy — nerve damage in the limbs and loss of coordination. That's a concern for over-supplementation, not for its presence in a balanced food.

Menadione is synthetic vitamin K3. The mechanism of concern is well established: it generates reactive oxygen species and depletes glutathione, causing oxidative stress that can damage red blood cells and liver cells — the route to hemolytic anemia. The FDA has banned it from over-the-counter human supplements, and doses as low as 10 mg have been linked to hemolytic anemia in susceptible people. ⚖️ In fairness: the FDA does permit it in animal feed, and over 50+ years of use there are no published reports of nutritional toxicity in dogs at pet-food inclusion levels — the studies showing harm used doses orders of magnitude higher, often injected or force-fed. Worth knowing too that neither K1 nor K2 is approved for pet food, so a manufacturer wanting to supplement vitamin K has no alternative. AAFCO does recognise menadione sodium bisulfite complex as a vitamin K source while noting that natural forms are preferred where available — which is roughly where the evidence sits. It's also worth knowing dogs synthesise vitamin K in the gut, so supplementation is rarely necessary in the first place; its presence often says more about the formulation being cheap than about the dog needing K. Our position: the mechanism and the human ban justify preferring foods without it, especially since dogs on a whole-food diet get K1 from plants and K2 from animal sources. We don't claim it has been shown to harm dogs at label doses, because it hasn't.

⚪ Formulation signal. The acceptable middle grade — adequately absorbed, behind zinc proteinate or zinc amino acid chelate, well ahead of zinc oxide. Not a reason to reject a food on its own.

⚪ Formulation signal, not a hazard. Sulfate is the adequate middle grade of mineral — better absorbed than oxide, not as well as a chelate, and mildly pro-oxidant. Iron proteinate or iron amino acid chelate is the upgrade. Seeing sulfates rather than oxides means the manufacturer did not buy the cheapest option available, which is worth knowing.

⚪ Formulation signal. Adequate absorption; manganese proteinate or amino acid chelate is better, manganese oxide is worse. On its own this is unremarkable.

⚠️ Read this one carefully, because it is flagged for the OPPOSITE reason to every other mineral here. As a form, sulfate is the acceptable middle — chelates absorb best, sulfates adequately, oxides barely at all. Copper sulfate is not a poor form. The concern is TOTAL COPPER LOAD: copper accumulates in the liver, dogs have no good way to dump the excess, and AAFCO deleted the copper maximum in 2007 and still has none. So 'meets AAFCO' tells you nothing about the ceiling. Matters most in copper-predisposed breeds — Bedlington Terrier, West Highland White, Doberman, Labrador, Dalmatian — where the target is under ~1.2mg per 1,000 kcal. Liver enzymes are NOT sensitive early, so normal bloodwork does not rule it out. Demoted from severe to mild on 2026-08-23: the form itself is fine, and scoring it as severe punished a mid-tier food for using an adequate mineral.

Sodium selenite is inorganic selenium, and selenium has one of the narrowest safe ranges of any nutrient. AAFCO sets the adult minimum at 0.35 mg/kg dry matter and the maximum at 2.0 — a window of only about 5.7x. For comparison, most nutrients have margins in the hundreds. That narrowness is precisely why the FORM matters here and matters less elsewhere. Two measured differences separate the forms. ABSORPTION: inorganic selenite is absorbed at roughly 50-60%, against 70-85% for organic selenomethionine and selenium yeast — so more selenite must be added to deliver the same nutrition, eating into an already tight margin. TOXICITY: comparative work found sodium selenite around 2.94x more toxic than selenium yeast, and organic forms test as less toxic than inorganic selenite and selenate generally. Mechanistically, selenomethionine is incorporated into proteins and released under regulation, whereas inorganic selenite generates free radicals during metabolism and causes oxidative stress in liver and kidney tissue; work in Biological Trace Element Research links long-term inorganic accumulation to kidney tubule damage that precedes any visible signs. So the case here is stronger than for most flagged ingredients: worse absorption AND higher toxicity AND the narrowest safety window in the profile. Prefer selenium yeast or selenomethionine.