Magnesium

Magnesium is a macromineral that powers hundreds of enzymatic reactions and underpins muscle and nerve function and bone structure; after [potassium](/glossary/potassium) it is the second most abundant cation inside cells. Dietary deficiency is rare with a complete food and would show as muscle weakness and cardiac disturbances. The most debated aspect of magnesium in feline nutrition is its part in struvite urinary stones, since struvite is magnesium ammonium phosphate and magnesium is one of its building blocks. For years, strict magnesium restriction was the standard advice for preventing these stones, but current understanding is more nuanced. The real drivers of struvite risk are urinary pH, hydration and infection by urease-producing bacteria, rather than magnesium alone (NRC, 2006). In fact, over-restricting magnesium in an acidified urine may tip the balance toward a different stone type, calcium oxalate, swapping one problem for another. Therapeutic struvite-dissolution diets are magnesium-reduced and urine-acidifying, but they are prescription products used under veterinary control, not everyday foods. Dietary magnesium comes from bone, some cereals and green vegetables, and a complete food provides a measured amount. The story is a useful reminder that single-mineral thinking rarely captures urinary health, which depends on the whole [calcium-to-phosphorus ratio](/glossary/calcium-to-phosphorus-ratio) and mineral picture. See the [Petipedia glossary](/glossary).

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