WHOLE FOODS CEO: We're Facing More Competition Than Ever Before

And future outlook isn't great for the grocer.

Whole Foods CEO John Mackey blamed the slowdown on other retailers wisening up and offering healthier, organic food in record numbers.

"Food retailing is more competitive than ever and with the growing demand for fresh healthy foods, it seems like everyone is adding to or expanding their offering of natural and organic products," Mackey said on a conference call with investors.

Demand for healthy and organic food has soared in recent years, which helped catapult Whole Foods' rapid growth.

But now, even big grocery chains like Wal-Mart have gotten on the healthy food train, giving customers more options than ever before.

Mackey said the brand would work on innovating stores and product selections to combat this problem.

Despite the growing competition, Mackey said he sees demand for at least 1,000 new Whole Foods stores in the U.S. alone. The retailer currently has 360 stores.