Prantil LR, Heinze CR, Freeman LM. Comparison of carbohydrate content between grain-containing and grain-free dry cat diets and between reported and calculated carbohydrate values. J Feline Med Surg. 2018 Apr;20(4):349-355.
From 2012 to 2014, the popularity of grain-free diets increased where the percentage of this type of cat food more than doubled, from 4% to 9% of total cat food purchased. Grain-free diets, instead of grains, usually contain alternate carbohydrate sources such as white potato, peas and other legumes, sweet potato or tapioca.
The aim is this study was to compare the carbohydrate content of grain-containing and grain-free dry cat diets and compare the major protein and carbohydrate sources of these diets. This analysis included a cross section of 77 randomly selected dry cat diets (42 grain-containing and 35 grain-free). In evaluating information on carbohydrate content, this value must be obtained from manufacturers and may be based on total starch, total sugars or, more commonly, nitrogen-free extract (NFE).
The authors also note that in addition to concerns about carbohydrates in cat foods, some clients report that they choose grain-free diets because of their perception that food allergies are common in cats and grains are a common allergen. The authors state that food allergies are reported to be uncommon in cats. If food allergies do occur, they are most commonly associated with animal-source proteins such as beef, chicken, fish or dairy protein than to plant ingredients such as wheat, corn or rice. It has not been reported that grain-free diets contain fewer of the most commonly reported food allergens just listed.
The authors report that the study determined that the mean manufacturer-reported carbohydrate content of the grain-free diets was 25% lower than the reported carbohydrate content of the grain-containing diets. However, there was considerable overlap between the two groups, while within each group individual diets varied widely in carbohydrate content. When comparing diets sold in specialty stores with mass-market diets, the carbohydrate content was higher in the mass-market diets than in the specialty diets, all inclusive of grain-free and grain-containing diets.
The grain-containing group contained eight categories of animal-sourced ingredients and 35 unique plant-sourced ingredients. In the grain-free diet groups, 10 categories of animal-sourced ingredients and 32 unique plant-sourced ingredients were identified.
In conclusion, the authors state these results indicate that selecting a grain-free diet is not necessarily a guarantee of lower carbohydrate content or fewer common food allergens are being fed (many common allergens are just as frequently found in grain-free diets). (VLT)