I actually ran into this problem a couple years back. I had some extra credits lying around that would have enabled me to take four courses a term, and still graduate on time. I ended up taking five courses a term anyway.
The issue here is that medical schools want to see that you can academically handle a medical school curriculum. This means lots of classes covering lots of material. Therefore, I chose not to take a lighter courseload, than what the typical, average applicant would have. Ideally, you should e-mail each of the medical schools that you are interested in, and ask them. My solution was to find an easy "filler" course that I thought I would enjoy and that wouldn't take much time away from my hard science courses. For me, that ended up being first year Economics.
I learned a lot, received good marks, and the time commitment compared to my Biochemistry class was minimal.