Sam's Club, Wal-Mart's warehouse retailer, has joined Costco in limiting sales of some rice to four bags per customer. Sarah Gardner reports on rising food prices and consumer habits.

Some of the world's poorest consumers in Africa and Asia have rioted recently over rising prices of wheat and rice. Economist Jeffrey Sachs, author of "Common Wealth," talks with host Kai Ryssdal about how more food riots and skyrocketing energy costs may be on the way.

Biofuels are getting blamed for a global food crisis and a setback in anti-poverty efforts. Fortune magazine's Allan Sloan examines the wisdom of growing things to make them into ethanol and considers alternatives.

With food prices on the rise, Sarah Gardner asks why it costs twice as much to make an omelette. She discovers cracking the price of eggs is quite the riddle.