Verdict: In moderation
Spinach is generally safe for dogs in small, cooked quantities. However, it contains oxalates which can be problematic in large amounts, especially for dogs prone to kidney issues. While not highly toxic, excessive intake can contribute to health problems.
Oxalates bind with calcium, forming calcium oxalate crystals. In large quantities, these crystals can accumulate in the urinary tract, potentially leading to kidney stones or impairing kidney function. They can also interfere with calcium absorption.
Oxalates (oxalic acid)