digestive intolerance to Ribose and Co-Q-10 in heart patient

My dad has heart failure.  I wanted him to use Ribose, and also Co-enzyme Q 10 for more energy and to make him feel better.  He said he tried Ribose once and it "made him sick" ; he tried one capsule of Co Q 10 and it "made him sick".  He was tested for colon cancer and found not to have that.  With co-Q 10, he said he had a small gray bowel movement when it made him feel sick.

What might be wrong with his stomach / digestive system so he could not appear to tolerate these supplements?  They are supposed to be so good for heart failure patients.

[patient915]

Welcome to the gastroenterology community!  If you dad has heart failure, you should check out all medications (which includes supplements) with his cardiology first before giving them to him.  I would recommend asking his cardiologist or a gastroenterologist about this.