Out of the three i would go with the regulation of dietary supplements. As to why? I think ppl would eat junk food no matter what. If thats what they wanted to do. You could put a skull and crossbones on a big mac and ppl would still eat it.
Dietary supplemetns on the other hand.We have a right to know what they are putting in those,and that they work as stated because alot are just crap.
Anyways that was just my two cents

Good luck on the speech..