Cabbage

Cabbage is on the AKC's list of vegetables dogs can eat, and it is a reasonable low-calorie crunchy treat: mostly water, decent fiber, and useful amounts of vitamins K and C. Raw or lightly steamed both work. The condition is that it arrives plain and chopped into pieces your dog can actually swallow, not as a leaf the size of its head. The real-world problem with cabbage is not poison, it is gas. Cabbage is a brassica, like broccoli and Brussels sprouts, and it ferments in the large intestine. A dog that gets a big serving of it for the first time can be visibly bloated within a few hours, with impressive flatulence and loose stool. That usually settles in a day or two. What is not normal is a distended abdomen combined with unproductive retching and restlessness — in a deep-chested dog that picture suggests bloat or GDV, and it needs an emergency vet immediately rather than a wait-and-see. Start with one or two small pieces and keep all treats inside 10% of daily calories. The second caveat is thyroid. Brassicas contain goitrogenic thiocyanates, which are irrelevant at treat volumes but worth a conversation with your vet if your dog is hypothyroid and on levothyroxine and you want to feed cabbage or broccoli daily in quantity. The forms to avoid are the American ones. Coleslaw is mayonnaise, sugar and often onion. Sauerkraut and kimchi are salt-loaded, and kimchi additionally contains garlic and scallion, both directly toxic to dogs. Cabbage cooked in bacon fat or braised with onion is likewise out. Plain is the whole point.