Review article summarizing available literature on the safety of Synthetic Amorphous Silica (SAS) as food additive E551

Core statement

E 551 has no toxic effect in the human body. The additive is among the most intensively investigated substances in toxicological studies. It has been used in the food industry since the 1950s.

The substance

E 551 is artificially produced amorphous silica, also known as synthetic amorphous silica. Over the decades, two production methods (wet chemical and pyrogenic) have become established, for which the resulting E 551 products are chemically identical. The additive is available for downstream processing as a powder or a granulate. It is important to note here that E 551 is not what is known as colloidal silica, which is a liquid with extremely finely divided nanoparticles.

Results in detail

  • Silica has no relevant toxicological effects. This has been confirmed in investigations where E 551 was repeatedly ingested orally in doses exceeding OECD recommendations; there was no indication of any negative consequences. In particular, no study indicated toxic strain on the liver, which is the body’s “detoxification center”. Nor is there any indication that ingested E551 damages genetic material or impairs physical development; damage to the immune and nervous systems can likewise be ruled out.
  • On ingestion, E 551 does not disintegrate into smaller particles in the acid medium of the stomach. Silica may have some limited solubility in the more alkaline medium of the intestinal tract. No known scientifically relevant study has shown any harmful influence of SAS.
  • The toxicological assessment is found to be identical for both of the established production methods.
  • These results are not surprising because many foods have a high natural content of silicon dioxide, which analytically almost cannot be differentiated from E 551.
  • E 551 is typically used in agglomerated form, and therefore does not contain free nanoparticles. The action of silica as a free flow agent in foods is based on the silica particles producing a certain separation between the food particles. The size must be optimal: Silica agglomerates that are too large, or too small, will not have the desired effect.

Type of study

A metastudy: The author has searched, analyzed, and summarized the existing scientific literature and the valid limit values.

About the author (as of 2016)

Claudia Fruijtier-Pölloth and her husband run CATS Consultants GmbH. The independent company, headquartered in Dietmannsried, specializes in approvals and toxicological matters. Fruijtier-Pölloth’s review article was commissioned by the silica industry.

Original publication:

Claudia Fruijtier-Pölloth, Arch. Toxicol. (2016), DOI 10.1007/s00204-016-1850-4