This is an excellent short NEJM article summarizing why the federal government does have the authority to mandate that people buy health insurance. Written by a Harvard Law School professor.
Einer Elhauge, J.D.
N Engl J Med 2012; 366:e1January 5, 2012
“Others argue that the Constitution’s framers could not possibly have envisioned a congressional power to force purchases. However, in 1790, the first Congress, which was packed with framers, required all ship owners to provide medical insurance for seamen; in 1798, Congress also required seamen to buy hospital insurance for themselves. In 1792, Congress enacted a law mandating that all able-bodied citizens obtain a firearm. This history negates any claim that forcing the purchase of insurance or other products is unprecedented or contrary to any possible intention of the framers.”