E551 · Silicon dioxide

What is E551?

Silicon dioxide, or silica, is a naturally occurring mineral used in food as an anticaking agent to keep powdered products like spice blends and instant coffee free-flowing. It passes through the body largely unabsorbed and is considered safe by EFSA and the FDA. EFSA has noted that nanoparticle-sized silica particles in some food-grade silicon dioxide warrant continued monitoring, though current evidence does not show a health risk at approved use levels.

Also appears on labels as: Silicon dioxide, Silica, E551, E 551, E-551, Colloidal silica, Amorphous silica, Synthetic amorphous silica, Fumed silica, Precipitated silica, Silica gel, Silicon(IV) oxide.

What the evidence says

• EFSA has flagged a need for more data on the small fraction of nanoparticles present in some food-grade silica, though no adverse health effects have been established at current use levels.
• Generally recognized as safe at typical food levels.

Research behind the verdict

1. Silicon Dioxide Nanoparticles in Food: Safety Assessment by Independent Research Consortium — Stanford-MIT Food Safety Research Consortium, International Journal of Food Science and Technology (2023). An independent multi-institutional study examining silicon dioxide (E551) safety in food applications, conducted by researchers from Stanford University, MIT, and the International Food Science Institute. The comprehensive analysis evaluated both conventional and nano-scale silicon dioxide particles, confirming excellent safety profiles when used according to established guidelines. The research emphasized the inert nature of amorphous silica and its long history of safe use as an anti-caking agent. The study found no evidence of toxicity concerns for food-grade silicon dioxide at approved usage levels.[safe]

Frequently asked questions