If its first-quarter results are any indication, Whole Foods Market (NASDAQ:WFMI) is still digesting its big mouthful of Wild Oats Market.

First-quarter net income decreased 27% to $39.1 million, or $0.28 per share. Revenues, however, surged 31% to $2.46 billion. Comps, which found themselves having to compete with an impressive 7% increase this time last year, rose by a notable 9.3% this time around. Perhaps Whole Foods should get more credit for its sales increases, especially since they're happening amidst worries about a consumer-spending slowdown and in the face of increasing competition from rivals such as Wal-Mart (NYSE:WMT), Safeway (NYSE:SWY), Kroger (NYSE:KR), and Trader Joe's.

In less exciting news, gross margin dipped by 10 basis points -- not too much of a surprise, since the first quarter is usually a lower-margin one for Whole Foods. In addition, economic value added, or EVA, a laudable metric that Whole Foods has always provided, fell from $10.2 million this time last year to negative $19.1 million for the quarter.

In the conference call, management seemed confident about the progress in integrating Wild Oats. However, a lot of work remains, including rebranding, relocating, and remodeling some Wild Oats stores, as well as closing down underperforming stores and converting the remaining ones to the Whole Foods' operating model.

Founder and CEO John Mackey implied, as he did last quarter, that worries about a recession or consumer slowdown shouldn't be a big problem for Whole Foods, since it has loyal organic customers, so the company is reaffirming its comps and sales guidance for the year. Whole Foods' historical performance during downturns seems to bear out Mackey's optimism. He also asserted that Whole Foods' prepared items are appealing to shoppers who are trading down from restaurants. And that argument seems perfectly logical when you consider the types of things strapped consumers do to cut costs, like eat at home more often.

Recalling the stock's surge last February, when the acquisition was announced, reminds me of how bipolar the market can be. Apparently, big news is exciting to many short-term-minded folks, but the actual execution of such a plan, which takes some time, is often too much to bear. I still feel confident about Whole Foods for the long haul; after all, its impressive sales increases tell me the brand and the business are thriving. Even if consumers are cutting back on their expenses, quality food and a pleasant shopping experience aren't things that the average Whole Foods customer is willing to scrimp on. And that strikes me as a major competitive advantage.  

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Whole Foods Market is a Motley Fool Stock Advisor recommendation. Wal-Mart is a Motley Fool Inside Value pick.

Alyce Lomax owns shares of Whole Foods Market. The Fool has a disclosure policy.