The economic climate may be rotten for grocery stocks in general, but Whole Foods Market (Nasdaq: WFMI) just proved that it's still made of the good stuff.

Whole Foods' first-quarter earnings increased 78.5%, to $88.7 million, or $0.51 per share. Sales increased 14%, to $3.0 billion, and comparable-store sales increased 9.1%.

Management apparently considers Whole Foods' reheated sales growth sustainable, since it boosted its guidance for the rest of the year. The company now expects a 10.7% to 12.8% increase in sales in fiscal 2011, and a 23% to 26% increase in earnings per share.

Whole Foods' tantalizing quarter reinforces fellow Fool Dayana Yochim's and my endorsement of Whole Foods as a solid pick last November. This is a smart contender in a difficult retail sector, as its continued financial performance proves.

Meanwhile, Wal-Mart (NYSE: WMT) struggles to increase its U.S. sales, and times are tough for grocery rivals like SUPERVALU (NYSE: SVU), Kroger (NYSE: KR), and Safeway (NYSE: SWY). While recent skyrocketing commodity inflation is a concern for all the names mentioned above, Whole Foods will likely be the most resilient, since its core clientele tends to be more affluent.

Conventional grocers likely won't be able to pass rising food costs along as readily, and their margins could suffer as a result. After all, there's a point at which financially strapped shoppers either won't or simply can't pay higher prices.

Whole Foods certainly looks like an expensive stock among its supermarket rivals; it trades at 35 times forward earnings, compared to a forward price-to-earnings ratio of 13 for Safeway and 12 for Kroger.

Still, as weaker rivals like SUPERVALU circle the drain, Whole Foods stands out as the grocer with the most enticing potential growth ahead. Whole Foods has only about 300 stores right now, so it has plenty of room for growth. Furthermore, it continually comes up with new initiatives to keep its customers engaged, and it's on top of many increasing trends, including the pursuit of healthy diets. Even now, Whole Foods' stock is worth the price.

Whole Foods is a Motley Fool Stock Advisor recommendation. Wal-Mart is a pick of Motley Fool Inside Value and Motley Fool Global Gains. Motley Fool Options has recommended buying calls on SUPERVALU. The Fool owns shares of SUPERVALU, and Wal-Mart. Try any of our Foolish newsletter services free for 30 days.

Alyce Lomax owns shares of Whole Foods Market. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.