Re: Silica Fiber Free canaryseed vs bird food quality Canaryseed [alpiste in Spanish] has been used as a dietary supplement for years, largely because of it's high percentage of iron and protein. Many say it has influenced their health, claiming it helps them maintain a healthy weight. Others say it supports normal health of the heart, blood vessels, liver, kidneys and pancreas. Silica fibers in bird food: There are some potential negative side effects with consuming bird food grade canaryseed, all of which contain microscopic silica fibers that are similar in structure to asbestos, and have been linked to esophageal cancer. Glabrous (Silica fiber free) varieties were originally developed to prevent skin irritation on farmers who handled bird food, with the additional benefit to those that consume "alpiste" as a dietary supplement.