The finish you apply will depend really on where the handles are to be used. If it is a high usage area such as a kitchen or bathroom a good sealant to protect from grease and moisture is recommended. The Feast Watson or Cabot's have some very good information.
Natural finishes are also available. Intergain timber oil, Osmo range of eco-friendly natural wood finishes or Quantum offer suitable products.
Wood Solutions interior finishes is an extremely good source of information. Scroll down the page a little to find a table which summarises different types of finishes, great to see at a glance.
If you are undecided after reading the infomation below, customer feedback about the Osmo product has been very good.