For the past 20 years, the demand for organic food has consistently grown by well over 10% per year. While Whole Foods Market (NASDAQ:WFM) was way out ahead of this movement, and has benefited from such prescience, the country's largest grocer has now decided to double-down on organics as well.

Believe it or not, one in every four grocery dollars every year is spent at Wal-Mart (NYSE:WMT).  Last week, after discovering through a survey that 91% of its customers would buy organic goods if they were priced right, the company announced that it was relaunching the Wild Oats brand.  By doing so, Wal-Mart claimed it was going to offer organic goods for prices much lower than could be found elsewhere.

Motley Fool contributor Brian Stoffel checked up on Wal-Mart's numbers. While they weren't quite as impressive as the company would have you believe, there's little doubt that Wal-Mart will offer competitive prices. But Whole Foods investors need not be too worried. In the video, Brian explains why, and which grocers really do have something to worry about.

Source: Wal-Mart, author trip to Whole Foods on April 11, 2014.

John Mackey, co-CEO of Whole Foods Market, is a member of The Motley Fool's board of directors. Brian Stoffel owns shares of Whole Foods Market. The Motley Fool recommends and owns shares of Whole Foods Market. Try any of our Foolish newsletter services free for 30 days. 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.