The more sodium you eat, the more fluid you'll retain while you're using prednisone. The University of San Francisco Medical Center recommends limiting yourself to 2,000 milligrams of sodium daily to help keep your weight under control. Avoid processed, canned and prepackaged foods in favor or fresh or frozen produce, low- or nonfat dairy products, whole grains and fresh, lean meat, seafood and poultry. If you do buy convenience items, look for low- or no-sodium varieties. Do not use high-sodium seasoning mixes when cooking or add extra salt at the table.