Can I substitute the Grapefruit?

Hey guys, just wondering if i can use some other fruit juice instead of grapefruit? Maybe lemon? I'm abroad at the moment and need to flush soon but I've asked everywhere and I can't get my hands on grapefruits. I'm worried the flush won't be as productive/successful if i use lemon or something. But then again, is the juice actually doing anything or is it just to help the oil go down? Tweet