The price trends of food and healthcare couldn't be more different. There's clearly something more than agricultural subsidies at work explaining the difference, given healthcare receives many fold more subsidies. In fact, it's possible that receiving compatively little in sibsidies is one reason that food prices have declined. An even more likely explanation for the price decline of food is that consumers are incentivizes to bargain hunt when buying food, since doing so reduces what they pay, and thus a real consumer-driven market, that rewards efficiency, exists in food. In healthcare, with private/government insurance, there is no incentive for consumers to bargain hunt.
Another factor that likely contributes to the divergence in prices is that healthcare is heavily regulated while food production is not anywhere near as constrained by government mandates.