Dyes are another unnecessary ingredient in dog food, since dogs do not care about the color of their food. This is strictly aimed at making products look more appealing to humans, for example by hiding the grey color of poor quality rendered products or visible variations in ingredients, or attempting to make a food look like it contains more meat by adding red dye.
While natural substances like caramel coloring are harmless, they are still unnecessary and generally only serve to make a food look more appealing and uniform to the human eye.
Science also tells us that food dyes are linked to serious disease. The Public Citizen Health Research Group has tried, unsuccessfully, to force the FDA to ban dyes linked to disease. They report that in 2005, over 6 ½ million pounds of Red #40, over 4 million pounds of Yellow #5, and over 600 thousand pounds of Blue #2 were used in pet foods and other products. Red #40 is linked to lymphomas, Yellow #5 is linked to allergies, thyroid tumors, and lymphocytic lymphomas, and Blue #2 is linked to brain tumors.
►Blue 2, Red 40, Yellow 5 and 6, other "numbered" dyes