Are your shoppers looking for a guilt-free snack, a food to stave off hunger pangs, a product that promises to improve athletic performance? There’s a bar for that. Many of today’s nutrition bars will meet your customers’ vegan, gluten-free, diabetic or raw dietary requirements as well. In fact, your choices for nutrition bars to stock are only growing—and in many ways improving.

“Companies are moving away from the tasteless, cardboard-like sports bars that strictly served a function because someone needed energy while scaling a rock wall,” says Brent Coons, product library director at Schaumburg, Ill.-based market research firm SPINS. “Manufacturers now realize the potential in positioning themselves as lifestyle brands with products suited to myriad needs.”

The innovation in this category is paying off. According to Nutrition Business Journal, U.S. sales of nutrition bars, energy gels and chews hit $2.5 billion in 2010, a 12 percent increase over 2009. NBJ predicts the category will add nearly $1 billion in new annual sales by 2013.

What do consumers want in a nutrition bar?

Ingredient-savvy shoppers need not check the labels of the latest nutrition bars hitting shelves to know what’s inside. See-through windowpane packaging, now considered a must by many manufacturers, makes chia seeds, oats, almonds, and other whole-food ingredients readily visible.

Consumers want products that speak to their health and wellness goals, so clarity at the store shelf is key. Shoppers also are increasingly looking for less-processed products that provide “functionality” from whole-food ingredients rather than from added vitamins, minerals and other nutritional ingredients.

Nutrition is far from the only factor driving nutrition bar sales, however. Products must also deliver on taste, and this is leading to what some experts are calling the “dessertification” of the category. Popular new flavors such as S’more, Chocolate Coconut and Rocky Road play up the indulgence factor, yet still deliver protein and whole grains with relatively few calories.

Here are our picks for five nutrition bars every natural products retailer should stock.