By Dr. Joe Wakshlag, D.V.M., Ph.D., "Are there foods that are good for humans that are not good for dogs?,"January/February 2013
While dark chocolate may be heart-healthy for humans, it’s the most toxic food a dog can eat. Chocolate contains theobromine, a compound that we can break down but dogs can’t, causing them heart problems, seizures and sometimes death. Onions—along with garlic and chives—contain a chemical that breaks down red blood cells in dogs and cats, causing anemia. The toxic effect is the same whether the onion is cooked, raw or even in flakes or powder. Lastly, too many grapes (or raisins) can also be deadly to dogs since grapes can cause kidney failure, though no one knows exactly why. If a dog eats one or two grapes, don’t worry. It takes quite a few!
Dr. Joe Wakshlag, D.V.M., Ph.D., nutritionist at the Dept. of Clinical Sciences at Cornell University College of Veterinary Medicine