Can dogs eat spinach?

The detail

Spinach gets recommended constantly in dog blogs for its iron and vitamins, and the nutrition itself is real. The problem is oxalic acid, which spinach carries more of than nearly any other vegetable in a UK kitchen.

Oxalates bind calcium in the gut, so the calcium in spinach is largely unavailable to your dog, and the surplus leaves through the kidneys. Vets Now advises serving spinach only occasionally for exactly that reason.

For a healthy dog on a complete food, an occasional tablespoon is nowhere near a problem. The dogs to keep it away from entirely are those with kidney disease or a history of calcium oxalate bladder stones.

The other trap is how spinach usually reaches the table. Creamed, buttered, or cooked down with onion and garlic, it stops being a vegetable question and becomes a dairy and allium one.

What oxalates actually do

Oxalate is a natural compound in plenty of plants, and spinach is one of the highest sources on a British shopping list. Raw spinach carries somewhere in the region of 600 to 900mg of oxalate per 100g, against single figures for most other greens.

In the gut, oxalate grabs calcium and forms calcium oxalate, which passes straight through. That is why the 99mg of calcium in 100g of spinach is largely unavailable to your dog.

Whatever the gut does not bind goes to the kidneys for excretion, and in dogs already forming calcium oxalate crystals that is the load you want to reduce. One tablespoon a week is a rounding error; a daily handful stirred into dinner is a habit worth stopping.

Raw or cooked spinach

Cooked is the marginally better choice. Boiling leaches some oxalate into the water, so cooked spinach with the water tipped away carries a little less than the same weight raw.

The reduction is modest and it does not change the verdict. Boiled spinach is still a high-oxalate food, and the portion sizes in the table above apply either way.

Raw baby spinach leaves are the version most likely to end up in a dog's mouth, usually out of a salad bowl. A few stolen leaves need no action beyond noting that they count towards the weekly amount.

Dogs with kidney problems or a history of bladder stones

These dogs should have no spinach. VCA Animal Hospitals is direct about it: dogs with calcium oxalate bladder stones should not be fed high-oxalate foods, and spinach is on the list.

The same caution applies to dogs on a prescription renal or urinary diet. Those foods are formulated to control mineral load precisely, and a handful of spinach undoes part of the calculation.

If your dog has had stones removed, has blood in the urine, or strains to pass water, the vegetable drawer is not where to start. Ring your vet.

Creamed spinach, saag and spinach dishes

Almost every cooked spinach dish is a no. Creamed spinach is butter, cream and often nutmeg, and many adult dogs digest dairy badly because they lose the enzyme that breaks down lactose after puppyhood.

Saag, spinach curries and most spinach side dishes are built on onion and garlic. Battersea lists both as foods that damage dogs' red blood cells, and cooking does not remove that. Our onion page covers what to do if a dog eats a dish made with them.

Spinach and feta pastries, spanakopita and spinach quiche add salt and pastry fat on top. If your dog polishes off a slice, the spinach is the least of it.

How much spinach is sensible

For a healthy adult dog, the honest answer is a tablespoon of plain cooked spinach about once a week, scaled by size using the table on this page. That is enough to satisfy the urge to add greens without stacking oxalate.

Chop it before serving, because wet spinach leaves clump and a dog swallowing a clump often brings it straight back. Serve it plain, with no butter, no oil, no salt and nothing from the allium family.

There is no nutritional reason to include it. A complete dog food already covers iron and the vitamins spinach is praised for, so treat it as an occasional extra rather than something your dog is missing.