" He is down on MRE's because he says they constipate "
My own experience from about 1980. I was at 29 Palms, Ca. as a support corpsman with a Marine tank company (reserves). My first time in the field. About the 3rd day, I mentioned to an experienced gunnery sargeant that I feared I was growing constipated; hadn't been to the "toilet" since our arrival. he asked me if I was eating the "candy" disks which came with our rations. (Can't remember now if they were C-rations or MRE's. Reservists took what we were handed and said thanks.) I ate a "candy" disk that evening and, the next day, lost probably 10 pounds of "used" rations. The gunnery sargeant explained the "candy" disks were a laxative to counter the lack of fiber in the rations.