Might help to know where you're planning to start and end as well as how long you think the trip will take. If you were going from SF to LA, I'd tell you dump most of your clothing. If you're planning to take several weeks worth of vitamins, I'd suggest that you're unlikely to get scurvy and suggest you leave them at home.

Edit: I'd ditch anything made of cotton, unless you're planning to stop at a laundromat when you need to wash stuff. Synthetics dry much faster and make hand-washing stuff in a sink practical.