Dear Daisy Dog: Please tell me the truth about grain-free pet foods. A pet store employee told me they’re healthier than diets with grains, but my veterinarian says they’re just a marketing gimmick.

Daisy Responds: Your veterinarian studied nutrition in vet school and is correct. Veterinary nutritionists agree that grain-free diets offer no special benefits, and no research shows them to be superior.

To understand, let’s start with the basics. Food ingredients provide nutrients – such as proteins, carbohydrates, fats, vitamins, minerals and water – which are substances needed by the body. So an ingredient, such as a grain, is simply a carrier of nutrients, such as carbohydrates, which the body uses to generate energy.

Grains contain not just carbohydrates, but also vitamins, minerals, fatty acids and protein. Interestingly, grain protein often is easier for dogs to digest than meat protein.

Actually, grain-free diets may be less healthful than grain-containing diets if they substitute starches, such as white potato or tapioca, which provide less fiber and fewer vitamins and minerals than grains.

Some people mistakenly believe dogs are allergic to grains. However, food allergy is uncommon in dogs, and when it occurs, the culprit most often is a meat protein.

So you don’t have to change pet food if your dog is doing well on his current diet. If he isn’t, ask your veterinarian for a recommendation.