Here's a look at how Walmart has dramatically altered the food system -- triggering massive consolidation, driving down prices to farmers, and leaving more families struggling to afford healthy food.

Campaigns across the country are underway to pressure the promised 1,500 Walmarts, SUPERVALUs and Walgreens to hire full-time employees from the neighborhoods they serve, sign labor peace agreements, and pay living wages.

Walmart announced changes that will improve the nutritional quality of the food supply. By 2015, all stores will be free of artificial trans fat and there will be enormous pressure on the rest of the food industry to follow suit.

WASHINGTON — Wal-Mart, the nation's largest grocer, says it will reformulate thousands of products to make them healthier and push its suppliers...