I agree with Jane, the hard skin around the heel does signal digestive problems. It is seen in people with OBS, Chrons, Cealiac Disease, or constipations and impacted fecal matter. Also when someone has their gall bladder removed, the area turns yellow and cracks. If the heel is yellowish and cracked and dry and the liver area is tender, and crunchy, it signals a sluggish liver too.
Way way back, at college, my lovely tutor told me is was the 'draining' area, where problems with the digestive system in general would be indicated, and if so, then the actual organ or place suffering, i.e. digestive tract, gall bladder, liver, intestines, etc., would be hard, lumpy, painful and crunchy.
I can honestly say if I spot this on a client, after one foot I then tell them what I have found and it is always correct, there is always some kind of digestive problem.
Love Gillyxxx