Is it okay for a golden retriever to have one pistachio?

No, golden retrievers should not eat pistachios. Pistachios are a type of nut that can be harmful to dogs. The high fat content can cause pancreatitis in some dogs. Additionally, pistachios contain tannins which can cause liver damage. The shells of pistachios can be dangerous as well, as they can cause obstructions in the digestive tract, potentially requiring surgery. It's best to avoid giving golden retrievers pistachios altogether.