Tough economic times haven’t taken a nip out of the natural and organic pet food business: Sales hit $1.3 billion in 2010, according to Nutrition Business Journal. And the products on offer go way beyond kibble and cans—from raw frozen meals and novel ingredients for the allergy prone (emu, sweet potatoes) to added nutrients (omega-3s, antioxidants) and virtuous label claims (organic, vegetarian, even human-grade).

“Manufacturers typically look at trends in human foods,” says Mukund Parthasarathy, PhD, a pet-food industry columnist and consultant to companies formulating products. “We want our pets to follow our own healthy lifestyles.”

Choosing the right food can be a complex equation, combining cost, personal values, and your animal’s unique health issues.

As a baseline, all pet foods labeled “complete and balanced” meet the standards of AAFCO (Association of American Feed Control Officials), an industry trade group that mandates minimum requirements for protein and key nutrients. Beyond that, there is little research to commend one food over another.

“Some ingredients certainly sound better than others, but there’s no comparative research, so it’s really a matter of faith,” says Marion Nestle, PhD, professor of nutrition at New York University and coauthor of Feed Your Pet Right (Free Press, 2010).

Shoppers should look at what’s important to them, Nestle says. Organic ingredients? Few or no grains? Vegetarian options? Your preferences may have as much to do with values as with nutrition, but once you know what you want, Nestle says, buy the best product you can afford.

Read labels for problem ingredients

“Get the product with the simplest ingredient deck possible, especially if your animal has problems with allergies,” says Susan Lauten, PhD, a pet nutritionist based near Knoxville, Tenn.

Allergies can manifest as itchy skin, ear infections, even chronic diarrhea. With a short-and-sweet list, it’s easier for you to know what your pet is eating and to eliminate problem ingredients for sensitive pets.

Though certain grains, especially rice, can be a great source of nutrition, grain-free products that supply carbohydrates from vegetable sources are often an excellent option for sensitive pets. “Look for food that does not contain commonly identified allergens such as wheat or wheat gluten,” says Edward Moser, DVM, a consultant for Wellness Pet Food.

Some pets also develop allergies to common protein sources, especially chicken and beef. (Soy can also be allergenic, so is best avoided, says Moser.) Many companies now use more unusual animal proteins, including lamb, ostrich, venison, and bison, which may be easier to tolerate. It can take a week or more on a new diet to notice changes.