I would seal them, dry wood is like blotting paper and will absorb whatever comes near it, if thats milk from your breakfast it can then go rancid. The perfect oil is one that cures or dries, tung is good, walnut is good if you don't have nut allergy, linseed is good but make sure its pure linseed without additives, I buy mine from horse feed merchants. If it was just a few bowls for myself I would use walnut...buy it anywhere they sell olive oil.