My bowls are all finished with food safe materials, such as linseed oil, walnut oil, beeswax, and carnauba wax.  Wipe with a damp cloth as needed; never put a wooden bowl in the dishwasher.  With use, you may find that the finish needs to be touched up a bit, which can be done with mineral oil or walnut oil.  A bit of beeswax will restore the natural luster.