Horse trading is a staple of politics. I'll vote for your bill if you support mine. But now there's evidence that Capitol Hill runs on a barter system even more rudimentary and potentially fattening: I'll charge your cell phone if you give me some potato chips.

The revelation comes from Politico (who else?), which discovered what it calls "black-market snack trading." The snacks are gifts from lobbyists in their districts or states: Coca-Cola supplies the Georgia senator, Pepsi the Kansas congressman because of the Wichita plant, etc. (Click the graphic below to see a detailed map of who's got what goods.)

Says Politico:

The covert snack economy is not just a way for hungry staffers to seek out chocolate-covered macadamia nuts from Hawaii or Lay’s chips from Texas. It’s a system for aides, especially low on the totem pole, to make friends, forge informal alliances and, ultimately, help keep Capitol Hill functioning.

So is the snack-food trade doing any harm? Well, it depends whether you're talking politics or health. It may come as no surprise that candy bars and potato chips are in the highest demand. Visitors to the office of one Democratic congressman from California are reportedly offered pistachios and prunes. Guess which runs out faster. The Florida delegation makes a fine orange juice trade.

Meanwhile, one Arkansas senator fills his office with artery-assaulting Little Debbie cakes. It's unclear whether sweet snacks pack more political influence than salty ones, but perhaps the free Swiss Rolls are a small insurance policy against going the way of the Twinkie in 2012. But there are healthy snacks floating around, including Chobani Greek yogurt in the offices of the New York senators. “You know what’s good currency? Chobani,” a House staffer told Politico. “People are trying to stay fit.”