Nano-structured silica food additive and its safety assessment
What it found
The authors say adverse effects from food-borne nano-structured silica particles cannot be excluded, based on their review of animal studies and lab tests.
They propose a lower daily intake limit than the one currently used.
What they found
Animal and lab studies
Animal feeding studies
In repeated-dose studies in rats and mice, most standard measures such as body weight, food consumption, blood tests and organ pathology showed no substance-related effects at various doses. Some studies reported liver effects, including fatty liver in mice given nano-sized silica and periportal liver fibrosis in rats after 84 days.
Long-term rat study
In a 103-week feeding study, rats given the highest doses of silica had lower body and liver weights. A few treated males had rare liver nodules and adrenal tumours that were not seen in control animals.
Uptake into the body
When rats were given silica particles by mouth, only a very small amount, estimated at 0.03 to 0.06 percent of the dose, appeared in tissues such as liver and spleen. No silica particles were detected in lymph nodes or other organs, so it is unclear whether the silicon found was still in particle form.
Survival through digestion
In lab tests mimicking human digestion, silica particles clumped together in stomach-like acid but broke apart again into nano-sized structures in intestinal-like conditions. Up to about 80 percent of swallowed silica particles were estimated to reach the intestine in nano-sized form.
Immune cell response
In lab tests, immune cells called dendritic cells released an inflammatory signal called interleukin-1 beta when exposed to silica particles after being activated by endotoxin. The authors say this shows the particles are not biologically inert.
Other findings
Dietary exposure estimate
Based on food products from a Dutch supermarket and a Dutch food consumption survey, the estimated daily intake of synthetic amorphous silica particles was 9.4 mg per kg body weight. Up to about 40 percent of the silica particles in those foods had an external diameter below 200 nm.
What the authors conclude
“Based on a critical review of existing oral toxicity studies, however, we consider that adverse effects from food-borne SAS particles cannot be excluded.”
Also in their conclusions
- They consider that adverse effects from food-borne SAS particles cannot be excluded.
- They advocate a prudent approach by taking an oral NOAEL of 500 mg/kg, based on body and liver weights in the 103-week feeding study in rats, as the point of departure for risk assessment.
- They say the estimated dietary exposure of 9.4 mg per kg body weight per day suggests that intake of SAS particles should be reduced to stay below their proposed safety threshold of 5 mg/kg per day.
How it was done
Nano-sized particles are increasingly used in food, but possible adverse health effects have received less attention. The authors wanted to review whether existing toxicity and risk assessment studies are adequate for judging the long-term safety of nano-structured silica added to food.
They reviewed published animal feeding studies, digestion experiments and immune cell lab tests on synthetic amorphous silica (E 551). They also recalculated a daily intake limit from a 103-week rat feeding study and compared it with estimated dietary exposure in a European population.
What it can’t tell you
- The animal studies reviewed cannot show what happens in people.
- The long-term rat feeding study was not checked for nutritional imbalances, so it is unclear whether some effects were caused by silica or by poor nutrition.
- The lab tests used immune cells and digestion models, not whole living animals or people, so they cannot show whether the same reactions occur in the human gut.
Who paid
- Authors work at
- University of Zurich-Vetsuisse, Switzerland; University of Zurich, Switzerland
The paper
- Title
- Critical review of the safety assessment of nano-structured silica additives in food
- Type
- ReviewThe authors read earlier studies and describe what they found. It isn’t a new study.
- Evidence
- Animals and lab studies
- Summarised from
- Full text
- Cite
- Winkler HC, Suter M, Naegeli H (2016). Critical review of the safety assessment of nano-structured silica additives in food. Journal of nanobiotechnology. doi:10.1186/s12951-016-0189-6Free full textPubMed 27287345DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error