Hamsters cannot eat lettuce in large quantities, but they can have it as a rare treat. Too much lettuce causes diarrhea and liver problems. Iceberg lettuce should never be fed to hamsters because of its high water content and lack of nutrients.
Safe fresh foods for hamsters include hard-boiled eggs, small amounts of fruit, parsley, cooked rhubarb, sweet potatoes, water spinach, squash, bell peppers and most herbs. While controversial, some pet owners feed their hamsters cooked meat, dog food, monkey chow and live mealworms to satisfy the hamsters' omnivorous nature. Other supplemental foods for hamsters include dry yeast and parakeet or canary seed.