Short answer: Spinach (Spinacia oleracea) is a leafy green Amaranthaceae vegetable native to central and western Asia, used in commercial pet food at modest inclusion (typically <2 percent) as a source of vitamin K1, iron, magnesium, folate, and the carotenoids lutein and zeaxanthin per USDA FoodData Central. Per Robertson 2002 (Vet Clin North Am) urolithiasis review and Lulich 2016 (J Vet Intern Med) consensus statement on canine calcium oxalate urolithiasis, spinach contains ~970 mg oxalate per 100g raw weight — among the highest oxalate concentrations of any commonly fed vegetable. Dogs with a history of calcium oxalate urolithiasis (most commonly Miniature Schnauzers, Bichon Frises, Yorkshire Terriers per ACVIM 2016) should avoid high-oxalate ingredients. The practical risk in commercial pet food is low because typical inclusion is 1–2 percent of formulation, contributing ~10–20 mg oxalate per 100g of finished kibble — an order of magnitude below intake associated with oxalate stone formation in susceptible dogs. Per AAFCO 2024 Official Publication, spinach is an accepted pet food ingredient. The KibbleIQ rubric treats spinach as a neutral functional inclusion at typical levels: it does not earn meaningful positive credit (modest nutrient density at <2 percent inclusion) but does not earn meaningful negative credit (oxalate exposure is sub-clinical at typical inclusion levels in non-predisposed dogs).

Botanical source and pet food inclusion form

Per USDA FoodData Central and Bergquist 2007 (LWT Food Sci Technol) leafy green nutrition review, Spinacia oleracea is a flowering plant in the Amaranthaceae family (formerly Chenopodiaceae), domesticated in ancient Persia and introduced to China by the 7th century and to Europe by the 12th century. Modern cultivars are categorized as flat-leaf (smooth-leaf), savoy (curly-leaf), or semi-savoy. Pet food formulations use spinach in three principal forms: fresh whole-leaf in fresh-frozen and gently-cooked premium formats, dried spinach powder in extruded dry kibble, and spinach extract in functional supplement positioning.

Per AAFCO 2024 Official Publication ingredient definitions, spinach is an accepted pet food ingredient under the broader vegetable category. Pet-food-grade spinach is typically a culinary-grade input meeting human-food specifications, distinct from the trim and stem material that would fall under broader by-product definitions. Inclusion levels in typical commercial dry kibble fall between 0.5 percent (decorative or marketing-positioning) and 2 percent (modest functional contribution). Fresh-frozen formats may include spinach at higher inclusion (5–10 percent of formulation) where the product is positioned around whole-food vegetable density. The whole-vegetable peer cluster overlaps with our carrots explainer and parsley explainer.

Nutrient profile: vitamin K, iron, folate, carotenoids

Per USDA FoodData Central (NDB 11457) and Roberts 2007 (J Food Compos Anal) leafy green carotenoid analysis, fresh raw spinach (100g) supplies approximately 28 kcal, 2.9g protein, 0.4g fat, 3.6g carbohydrate (2.2g fiber), 483 mcg vitamin K1 (4-fold the AAFCO canine adult requirement on a per-100-kcal basis), 2.7 mg iron, 79 mg magnesium, 194 mcg folate, 9420 IU vitamin A activity from beta-carotene, 28 mg vitamin C, and substantial lutein + zeaxanthin (~12,200 mcg combined per 100g per Bone 2007 J Nutr).

Per AAFCO 2024 Official Publication canine adult vitamin K1 minimum (no required minimum — canine intestinal flora synthesizes adequate vitamin K under normal conditions) and feline adult minimum (1 mg per kg dry matter), spinach’s vitamin K density is functionally meaningful. Iron contribution at 2.7 mg per 100g is modest relative to the 80 mg per kg dry matter canine adult AAFCO minimum, supplying ~3 mg per kg dry matter at 1 percent inclusion. Folate (vitamin B9) contribution is meaningful for puppy growth and reproduction formulas. The carotenoid framework overlaps with our lutein explainer, zeaxanthin explainer, beta-carotene explainer, and folate explainer.

Oxalate content and calcium oxalate urolithiasis context

Per Robertson 2002 (Vet Clin North Am) urolithiasis review, Lulich 2016 (J Vet Intern Med) ACVIM consensus on canine calcium oxalate urolithiasis, and Stevenson 2003 (J Anim Physiol Anim Nutr) dietary oxalate review, spinach contains approximately 970 mg oxalate per 100g raw weight — among the highest oxalate concentrations of any commonly fed vegetable. Other high-oxalate ingredients include rhubarb (~860 mg/100g), beet greens (~610 mg/100g), Swiss chard (~645 mg/100g), and cocoa (~700 mg/100g). The oxalate is present primarily as soluble oxalate (calcium-binding) plus modest insoluble calcium oxalate.

Calcium oxalate urolithiasis is the second-most-common canine urolith type after struvite, accounting for ~40 percent of canine bladder stones submitted to the Minnesota Urolith Center per Lulich 2016. Predisposed breeds include Miniature Schnauzers, Bichon Frises, Yorkshire Terriers, Lhasa Apsos, Shih Tzus, and Cairn Terriers. In affected dogs, dietary oxalate restriction is one component of a multi-factorial dietary management strategy that also includes urine alkalinization, increased water intake, and dietary calcium and protein moderation. The practical risk in commercial pet food is low at typical inclusion levels: at 1 percent inclusion, finished kibble contributes ~10 mg oxalate per 100g, well below the ~50 mg per 100g threshold typically associated with stone formation in susceptible dogs per Stevenson 2003. The urolithiasis framework overlaps with our best cat food for urinary health guide.

Cooking, blanching, and oxalate reduction

Per Bergquist 2007 (LWT Food Sci Technol) and Chai 2005 (J Agric Food Chem) cooking effects on vegetable oxalate, blanching and boiling reduce soluble oxalate content of leafy greens by approximately 30–50 percent through leaching into cooking water that is subsequently discarded. Steaming preserves more soluble oxalate than boiling. The pet food formulation implication is that gently-cooked or extruded spinach in commercial pet food retains a substantial fraction of original oxalate content; typical processing does not eliminate the oxalate concern but neither does it amplify it.

Calcium binding of dietary oxalate in the gut lumen reduces oxalate bioavailability for renal filtration and stone formation per Hess 1998 (Br J Nutr). Calcium-rich pet food formulations (typical commercial extruded kibble at 1.0–1.5 percent calcium) provide ample lumen calcium to bind dietary oxalate from spinach inclusion at typical levels, further reducing the practical urolithiasis risk in non-predisposed dogs. Dogs with documented calcium oxalate urolithiasis history should be fed prescription veterinary diets formulated for oxalate management (Hill’s Prescription Diet u/d, Royal Canin Urinary SO, Purina Pro Plan UR St/Ox), which omit high-oxalate ingredients including spinach. The prescription urinary framework overlaps with our best dog food for kidney disease guide.

How KibbleIQ scores spinach

The KibbleIQ Dry Kibble Rubric treats spinach as a neutral functional inclusion at typical pet food levels (0.5–2 percent of formulation). Spinach in the ingredient list does not earn meaningful positive rubric credit because the vitamin K, iron, folate, and carotenoid contributions at <2 percent inclusion are modest relative to the supplement-form vitamin and mineral premix that supplies these nutrients in any AAFCO-complete formulation. Spinach also does not earn meaningful negative rubric credit at typical inclusion because oxalate exposure is sub-clinical for non-predisposed dogs and adequately bound by the calcium content of typical commercial extruded kibble.

For dogs with a documented history of calcium oxalate urolithiasis, the rubric’s neutral treatment of spinach should be supplemented with a veterinary recommendation to feed prescription veterinary diets formulated for oxalate management. To check whether your dog’s food contains spinach or peer high-oxalate ingredients, paste the ingredient list into the KibbleIQ analyzer. For peer whole-vegetable context, see our carrots explainer, parsley explainer, pumpkin explainer, and sweet potato explainer. For methodology context, see our published methodology.