Lettuce is safe to feed to dogs in limited quantities; but it is difficult for dogs to digest, and it offers limited nutritional value. Since lettuce is high in fiber, it can supplement a dog's diet on occasion and provide relief for constipation. Too much lettuce can cause digestive problems.
Steamed lettuce is recommended, as most of the vitamins are preserved during this process. Dogs are omnivorous and can eat a variety of fruits and vegetables, especially compared to cats. However, many household foods can be toxic to dogs, including chocolate, grapes, raisins, macadamia nuts and onions. Vomiting, abdominal pain and loss of coordination are signs of poisoning in dogs.