Is silica safe as a food additive (E 551)?

In the EU, synthetic amorphous silica (SAS) used as a food additive has the identification number E 551. Extensive tests have been carried out regarding the effects of SAS on humans, animals, and the environment. In food, SAS is used only in very small quantities and to date no adverse health effects have been reported. But even in larger amounts, it is safe to consume.
E 551 is also tested regularly by the European Food Safety Authority and is approved as an additive in the EU. As with all “E numbers”, this approval is an official guarantee to all consumers that the additive is safe and can be used without any concerns.

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Synthetic amorphous silica (SAS) meeting the specifications in Regulation (EU) No. 231/2012 has been approved for use in the European Union (EU) as food additive E 551 and is regularly reviewed by the European Food Safety Authority (EFSA) with regard to its safety. The most recent assessment was made public in January 20181:

- All of the studies used for this assessment found that E 555 has no toxicologically relevant effects.
- The highest dose tested at which no toxicological effects were found is significantly higher than the estimated exposure level of a normal consumer.
- The EFSA recommends continued data collection—a chronic toxicity study in particular—in order to define the acceptable daily intake (ADI).
- The EFSA further recommends updating E 551 specifications with respect to heavy metal thresholds and particle size distribution. 
To summarize, the EFSA reevaluation has confirmed the safety of E 551 as a food additive.
The form in which SAS is added to food DOES NOT correspond to the current recommended definition of nanomaterials given in Regulation (EU) No. 1169/2011 (the provision of food information to consumers) or in Regulation (EU) No. 2283/2015 (novel foods). As such, the term “nanosilica” should not be used in conjunction with the use of SAS as a food additive.

E 551 is one of the most intensively investigated substances and to date there have been no indications of adverse health effects in cell cultures or in animals, even with high doses that could not normally be absorbed via food. Recently, a study from the Netherlands (Van der Zande et al., Particle & Fibre Tox. (2014)) was published in which indications of possible fibrotic liver changes in rats after repeated application of SAS by gavage tube over a period of three months were reported. This publication was not carried out according to the OECD guideline and contains blatant discrepancies; when this study was reassessed, no reliable effects were determined. This is in agreement with the overall result from the recognized expert for nanotoxicology, Professor Harald Krug, who has evaluated the relevant literature extensively during the last ten to twenty years: “Most studies do not make a clear statement about the safety of nanomaterials”. On the contrary, the majority of the studies are either contradictory or come to a completely erroneous conclusion (Fruijtier-Pӧlloth, C. Arch Toxicol (2016)).

None of the studies that were conducted according to the valid guidelines showed any indication of health-damaging effects of SAS on the liver or any other organ system, including the nerve and immune systems. It is very important to comply with the applicable guidelines to prevent over-dosage and measurement errors. This also allows different studies to be compared. 

 1EFSA ANS Panel (EFSA Panel on Food Additives and Nutrient Sources added to Food), Scientific Opinion on the re-evaluation of silicon dioxide (E 551) as a food additive. EFSA Journal 2018;16(1):5088, 70 pp