Silicon Dioxide | whatsinit

About

What it is and where it shows up.

Silicon dioxide (silica) is a naturally occurring inorganic compound used in food as synthetic amorphous silica (SAS) — an anti-caking agent that prevents powdered and granulated foods from clumping — and as an anti-foaming agent and carrier in food supplements. The food-grade form consists of nano-sized constituent particles forming larger aggregates, produced via fumed (pyrogenic) or wet (precipitated/gel) manufacturing routes.

Safety summary

The regulatory and scientific consensus.

EFSA's 2024 re-evaluation concluded that E551 does not raise a safety concern in any population group, including infants under 16 weeks, at current permitted use levels; no formal ADI has been set and the earlier SCF ruling classified it 'ADI not specified'. Minor concerns exist around trace impurities (lead, mercury, arsenic, aluminium) in commercial preparations and the nano-scale character of SAS aggregates, for which EFSA has recommended tightened EU specifications. Only the crystalline form of silica — not the amorphous SAS authorised in food — is classified by IARC as a Group 1 carcinogen (by inhalation in occupational settings).

Regulatory landscape

What food-safety regulators have decided.

Jurisdiction	Status	Note
EFSA (European Food Safety Authority) (European Union)	Approved	Authorised under Regulation (EC) No 1333/2008, Annex II and III; purity criteria in Commission Regulation (EU) No 231/2012; SCF (1991) set group ADI 'not specified' for silicon dioxide and silicates; re-evaluated by EFSA ANS Panel in 2018 (EFSA Journal 16(1):e05088) and by FAF Panel in 2024 (EFSA Journal 2024:8880); EFSA recommended lowering maximum limits for lead, mercury and arsenic in E551 specifications and improving nano-particle size characterisation.source
FSSAI (Food Safety and Standards Authority of India) (India)	Approved	Approved as INS 551 (Silicon dioxide, amorphous) under FSS (Food Products Standards and Food Additives) Regulations, 2011; permitted in salt and salt-based products at GMP (quantum satis) level; a product-specific application (No. 19/Std/PA/FSSAI/2019) was approved on 15 January 2020 under FSS (NSF & FI) Regulations, 2017.source
FDA (Food and Drug Administration) (United States)	Approved	Permitted as a direct human food ingredient under 21 CFR 172.480 at a maximum of 2% by weight of food; also covered by multiple GRAS notifications including GRN 321, GRN 554 and GRN 996 for synthetic amorphous silica (silica gel form).source

Who should approach with care

Whose guidance would steer them away.

Infants — EFSA (2024) concluded no safety concern for infants under 16 weeks at current use levels, but explicitly noted a lack of direct hazard data for this age group and uncertainties around isolated nanoparticle fractions; caregivers should consult a doctor before routinely feeding products containing E551 to very young infants.

Kidney Disease — Silicon is primarily excreted renally; while no formal regulatory restriction exists for this group, individuals with significantly impaired renal function may have reduced clearance of any absorbed silicon-containing material and associated trace impurities such as arsenic and lead.

Pregnancy — EFSA (2024) flagged trace heavy-metal impurities (lead, mercury, arsenic) in commercial E551 as a concern for the general EU population; pregnant individuals represent a sensitive group for heavy-metal exposure, and EFSA has recommended lowering impurity limits to reduce population-wide exposure.

Research citations

The sources behind this verdict.

1FDA. 21 CFR 172.480 – Silicon Dioxide. accessdata.fda.gov
2PubMed. Re-evaluation of silicon dioxide (E 551) as a food additive in foods for infants below 16 weeks of age and follow-up of its re-evaluation as a food additive for uses in foods for all population groups, 2024. pubmed.ncbi.nlm.nih.gov
3EFSA. Re-evaluation of silicon dioxide (E 551) as a food additive in foods for infants below 16 weeks of age and follow-up of its re-evaluation as a food additive for uses in foods for all population groups, 2024. efsa.europa.eu
4FSSAI. Food Safety and Standards (Food Products Standards and Food Additives) Regulations, 2011 – Compendium of Food Additives Regulations (Version March 2022), 2022. fssai.gov.in
5FSSAI. Food Safety and Standards (Food Products Standards and Food Additives) Regulations, 2011 – Compendium (Version as of March 2022), 2022. fssai.gov.in

Independently researched8 citations