In general, yes, Jains can eat lettuce.

Lettuce is a leafy vegetable, and it is commonly accepted in Jain food practices because it is not a root vegetable. In Jainism, the main restriction is to avoid root vegetables such as potato, onion, garlic, carrot, beetroot, radish, etc., because uprooting the plant destroys more life.

So:

• Lettuce: generally allowed
• Root vegetables: not allowed

If eaten, it should still be with ahimsa in mind: clean, fresh, and prepared carefully to avoid harming living beings.