It is not there to buy food and stuff directly with Bitcoin. It is used along with Gold and other stable assets to preserve the value of an high inflationary local currency. If you need some cash (at the current exchange rate) you just sell some bits for cash in order to buy food with.

Here are two links to this topic:
The Guardian: Growing number of Venezuelans trade bolivars for bitcoins to buy necessities
Aljazeera: Venezuelans turned Bitcoin Mining