What E551 actually is
Silicon dioxide is silica, the same compound as sand and quartz, refined to a very fine powder. Its job is to stop powders clumping: it coats particles so they slide past each other instead of sticking. Without it, powdered drink mixes, grated cheese, and spice blends would set solid.
What it is made from
Produced either from sand by a thermal process or by precipitation from silicate solutions. It is a mineral, not a plant or animal product.
Vegan, vegetarian, and halal status
Silicon dioxide is mineral-derived with no animal or plant input, so it is suitable for every dietary requirement.
Is E551 safe?
EFSA re-evaluated silicon dioxide in 2018 and could not confirm a numerical intake limit, not because of evidence of harm but because the available data on particle size was incomplete. It asked for better characterisation of the nanoparticle fraction. The additive remains permitted in the EU, UK, and US. This is worth stating precisely, because it is often reported as EFSA raising concerns when what actually happened was EFSA asking for more data on particle size distribution.
- Largely unabsorbed by the digestive system
- EFSA asked for better nanoparticle characterisation in its 2018 re-evaluation, and no intake limit is currently set
- The inhalation hazard from crystalline silica dust in industry does not apply to eating the food-grade amorphous form
Where regulators stand
- EFSA (EU)
- Re-evaluated in 2018. No acceptable daily intake established pending better data on particle size. Remains permitted.
- FDA (US)
- Generally recognized as safe, with a limit of 2 percent by weight.
Foods it turns up in
- Powdered drinks and instant products
- Grated and shredded cheese
- Spice blends and seasoning
- Table salt
- Supplements and tablets
Names it hides behind
- E551
- Silicon dioxide
- Silica
- Anti-caking agent (E551)
- Amorphous silica
Common questions
- Is silicon dioxide safe to eat?
- It is permitted in the EU, UK, and US and passes through largely unabsorbed. EFSA's 2018 re-evaluation asked for better nanoparticle data rather than reporting evidence of harm.
- Is eating silica the same as the sachets in packaging?
- No. Those sachets are silica gel desiccant marked do not eat, which is a different form and a different purpose. Food-grade silicon dioxide is a permitted additive in the food itself.
- Is silicon dioxide vegan and halal?
- Yes. It is a mineral with no animal or plant origin.
- Why is it in grated cheese?
- Grated cheese would otherwise clump into a solid mass in the bag. A small amount of anti-caking agent, sometimes silicon dioxide and sometimes cellulose, keeps the strands separate.
- Does the body absorb silicon dioxide?
- Very little of it. The great majority passes through the digestive tract unchanged.
Checking a real pack
This page answers the code. The pack in your hand is what decides, because the same code can come from different sources depending on the manufacturer. LabelWise, formerly SafeChoice, scans the label and explains what is in front of you.
Related
LabelWise content is educational and describes how additives are made, regulated, and labelled. It is not medical, dietary, or religious advice. For certification questions, the mark on the pack and the certifying body are the authority.