Olive oil is great. Take a tablespoon every night before bed, wash it down with fruit juice, I prefer cherry. For the rest of your life.
Your liver needs vegetable oils to function properly. The body needs the Omega 3's from the vegetable oils for many functions. Calcium transport, hormone levels, joint repair, blood viscosity, nerve function, etc. etc.
Olive oil and flaxseed oil are the two main oils to take. Whatever your body prefers. Mine prefers olive oil, my wife flaxseed oil. It maintains proper liver function and lubricates the small intestine for proper movement through the intestine and nutrition absobtion. Thus, it does help move you if you're constipated.