Magnesium citrate
"I had been very constipated since I started dieting and losing weight. I was hardly pooping at all and it was making my stomach feel very uncomfortable. I started taking miralax but that takes days to work for me. So for immediate relief I picked up some mag citrate. I drank the whole 10 ounce bottle lemon flavor. It tasted tolerable but not great. After 2 hours still no results so I drank 3 big glasses of water and bam, after 10 more minutes I was on the toilet. This WILL give you watery diarrea so be prepared but the relief is amazing"