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Minerals in dog and cat food: new study from Santiago University

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Quick answer: a systematic review from the University of Santiago de Compostela, published on 16 October 2026, concludes that mineral imbalances (calcium, phosphorus, zinc, copper, selenium and others) appear in every type of diet, but are more frequent and more variable in home-made and raw (BARF) diets. A high price does not guarantee better mineral supply. The safest option is a complete food and, if you cook yourself, a recipe designed by a veterinary nutritionist.

Minerals make up a small part of the ration, but a decisive one: calcium and phosphorus support bones and teeth, zinc and copper play a role in skin, coat and immunity, and selenium protects cells. A long-term excess or shortfall can take its toll. That is why the paper just published by the Faculty of Veterinary Medicine in Lugo in the scientific journal Animals is newsworthy.

What the study looked at

Researcher Marta López-Alonso and her team screened around 8,000 publications from 2005 to 2025 and selected 76 studies: 58 that measured minerals in different foods in the laboratory and 18 that estimated intake from labels, ingredient tables or owners’ recipes. The results were compared with the nutritional guidelines of FEDIAF, the European pet food industry federation.

The findings: raw and home-made diets vary more

  • Imbalances were found in every category, including conventional kibble. Some cat foods had high phosphorus with a low calcium-to-phosphorus ratio.
  • Alternative diets repeatedly showed shortfalls in copper, iron, manganese, selenium and zinc, while calcium and the calcium-to-phosphorus ratio were often off target in raw-meat, home-made and some plant-based diets.
  • Variability is much greater in home-made food: in one study, 60% of 95 owner-prepared rations had at least one imbalance.
  • Pricier is not better: price or premium positioning did not reliably predict better mineral adequacy, and there is no general rule between dry and wet food.
  • On very restricted weight-loss diets, selenium, magnesium and potassium intake can fall short even when the food looks fine on paper.
  • Fish-based foods were more often linked to arsenic and mercury, although results varied widely between studies.

The authors call for more standardised testing methods and better monitoring of pet food: only 24 of the 58 analytical studies used certified reference materials.

What it means for you

If your pet eats a “complete” dry or wet food, it already gets a formula designed to meet its needs, as long as you follow the feeding guide on the label. If you prefer raw feeding or home cooking, the study confirms what vets keep saying: improvising recipes is risky, because a lack of calcium or trace elements can go unnoticed for months.

Practical tips

  • Check that your pet’s main food says “complete feed” and suits its species and life stage.
  • If you cook or raw feed, ask for a recipe formulated by a vet specialising in nutrition and do not add mineral supplements on your own.
  • If your cat almost always eats fish recipes, rotate with other proteins.
  • If your pet is on a weight-loss diet, book regular check-ups with your vet.

See more dog food, dry cat food and wet cat food.

Frequently asked questions

Is raw feeding worse than kibble?

The study does not say one diet is always better, but it does show that raw and home-made diets have more imbalances and far greater variability. With a professional recipe that is followed carefully, the risk drops.

Should I give my dog calcium supplements?

Not without veterinary advice. Too much calcium is harmful too, especially for large-breed puppies. If the food is complete, it is usually unnecessary.

Does expensive food have better minerals?

According to this review, price does not reliably predict better mineral supply. Make sure the food is complete and suited to your pet’s life stage instead.

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