As Issac points out, one problem with cryogenic sleep for long space journeys is that, over years of stasis, even mildly radioactive isotopes will destroy your body faster than it can repair itself. (Because you are in stasis you are not repairing yourself.)
So one solution is to spend about 5 years eating, drinking and breathing in an environment that has been scrubbed of all of these isotopes, until almost all of the atoms in your body are replaced. The cores of asteroids would be a plentiful source of carbon without carbon-14, though I guess you'd need a gas centrifuge to eliminate other elements like potassium-40.
In either case, you and your crewmates would live in a giant closed cycle biosphere 'waiting room' full of crops, soil, trees and water for 5 years prior to being frozen for your thousand-year interstellar journey.