Why are plant-based proteins penalized?
Plant proteins like pea protein, soy isolate, and corn gluten meal inflate the protein percentage on the label but don't deliver the same nutritional value as animal protein for cats.
This is one of the most common sources of misleading marketing in cat food. A bag can say "High Protein - 40%!" while that protein is largely coming from peas and corn - not meat.
The problem with plant protein for cats
Cats are obligate carnivores. Their digestive systems and metabolic pathways are specifically adapted to animal protein - not plant protein. The two are not interchangeable.
Plant proteins do not contain taurine - an amino acid essential for cats that their bodies cannot synthesise. Taurine deficiency causes dilated cardiomyopathy (heart disease) and retinal degeneration.
They also lack arachidonic acid and have lower levels of the specific amino acid ratios cats need for organ function.
Protein is measured as total nitrogen content. Plant proteins - especially concentrated isolates like pea protein - are very high in nitrogen, which makes them look like excellent protein sources on paper.
But cats cannot utilise plant protein the way they use animal protein. High total protein from plants doesn't translate to good nutrition for an obligate carnivore.
Watch for these in the ingredient list - especially high up:
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Pea protein / pea protein isolate
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Corn gluten meal
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Soy protein isolate
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Wheat gluten
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Potato protein
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Chickpea / lentil protein
Their presence near the top of the ingredient list is a strong signal that they're being used as a cheap protein booster.
The fix is simple: look for named animal ingredients in the first three positions of the ingredient list. If you see plant protein isolates in the top five, expect a scoring deduction under Rule 3.
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