The amount of food Walmart sold grew at the fastest pace in four years, according to CFO John David Rainey, who noted rising sales of gluten-free items, grass-fed beef and organic produce, particularly in pick-up and delivery orders.

Walmart may have started out as a retailer geared to budget-sensitive consumers, but its customer base is continuing to grow, thanks to more affluent shoppers. The retailer saw share gains in new shoppers across income levels mainly led by upper-income households,