Is 551 vegan?

In this brief guide, we will answer the query, “Is 551 vegan?’ and will discuss the use and risks of E551.

Is 551 vegan?

Yes, E551 is vegan. E551 is also known as silicon dioxide. Since it is only a mineral found in sand, rocks, and the Earth’s surface, silicon dioxide (silica) is vegan. It is not a product of animal origin.

What is silicon dioxide?

Silica, often known as silicon dioxide or silica, is a naturally occurring compound made up of silicon and oxygen. Silica comes in a wide variety of forms. They all have the same composition; however, they may be referred to by various names based on the arrangement of the particles. Amorphous silica and crystalline silica are both forms of silica. 

It has been widely used as an anticaking agent and a carrier since the 1950´s. The specific criteria for its safety and use, the Commission Regulation (EU) No. 231/2012 contain the two production methods with which synthetic silica is made: the thermal process and the wet process. These processes result in solid silica products of identical chemical composition either as anhydrous products (pyrogenic silica, produced by the thermal route) or as hydrated products (precipitated silica, silica gel, or hydrous silica; all produced by the wet route). E 551 is produced as fluffy fine powder or granules in the micrometer size range, a ca. 20–30 nn micrometer granules as typically contained in products delivered to the customer (1). 

Western diets are closely related with ongoing epidemics of obesity, hypertension, diabetes, atherosclerosis, Chron’s disease, coronary artery disease, behavioral disorders and cancer, moreover, approximately 35% of cancer cases are related to nutrition. Ultra-processed products, such as sweets, fatty or salty packaged snacks, confectionery candies, cookies, pastries, dressings, powdered and packaged instant soups, noodles and even baby formulas, among other products are highly consumed in western diets and contain food additives such as flavor enhancers, colorants, emulsifiers, artificial sweeteners, thickeners and foaming and antifoaming agents (4).

Occurrence in nature

Natural silicon dioxide may be found everywhere. What the ATSDR (Agency for Toxic Substances and Disease Registry) has to say about the prevalence of this substance is enlightening. Quartz is the most frequent term for this mineral, which accounts for around 12 percent of the Earth’s surface. Aside from water and plants and animals, silicon dioxide may be found naturally. Many beaches are covered with silica sand, which is also found in most of the rocks on the planet. More than 95 percent of the Earth’s crust is made up of silica-containing minerals or silica itself. 

In addition to its use as a food additive, E 551 is also used in cosmetics (e.g. as abrasion additive in toothpastes), in pharmaceuticals (e.g. as free-flow additive, carrier, or retardant agent and as tableting aid), and in dietary supplements (e.g. as dispersive medium for vitamins). In food supplements, silica is added up to a level of 700 mg silicon/day. Estimates on the intake of E 551 contained in pharmaceutical formulations are not available. Very low levels (<0.2 %) are required when used as a glidant for tablets, the most common medicinal application. Toothpaste may, however, contain relatively high amounts of E 551, which in part may be swallowed (1).

Many plants that people commonly eat also contain silicon dioxide, such as (1):

·         Greens that are rich in chlorophyll

·         Oats, brown rice, and vegetables like beets and bell peppers are also good sources of silica.

·         Alfalfa

Why is silicon used as a food additive?

Silicon dioxide is utilized in food additives because of its ability to absorb water. It is used in the production of everything from glass to cement, but silica may also be used to enhance and protect food products. To prevent food from caking or clumping together, this sort of food ingredient is used. Preventing powdered components from sticking together and clumping together may assist in extending the shelf life of a product and protecting it from the impacts of moisture.

E 551 exerts its function as anti-caking agent mainly by covering the surface of host powders and thus acting as a spacer, and through its water adsorption capacity. Similarly, silica particles may adsorb to cellular surfaces and proteins and may thus affect biological membrane structures and integrity. The technical function of E 551 is to act as a spacer between food components in order for them to remain in a free state; nanosized particles are actually not desired because they are too small to enable this effect. The spacer function can only be achieved by the silica aggregates and agglomerates having size ranges which are typically greater than 100 nm (1).

Silicon dioxide’s safety

People who care about what goes into their food are often wary of chemicals like silicon dioxide.

Silicon dioxide is a naturally occurring chemical, despite its unusual name. Many studies have shown that silicon dioxide is safe to eat in modest quantities, such as in food items that are meant to keep them from caking.

The European Food Safety Authority (EFSA)Trusted Source has published a review of silica research. When animals were fed silica regularly in animal models, no silicone buildup was seen. People should also be aware that silica comes in a variety of grades. Cement companies, for example, employ silica that is not the same quality as the silica found in dietary supplements (2).

Silica is also regulated by the Food and Drug Administration (FDA) in the United States. Following FDA rules, producers may use silicon dioxide as a food additive as long as they use only the lowest amounts necessary and the quantity does not exceed 2% by weight of the food product.

Silicon dioxide in its various forms was tested intensively in toxicological, genotoxic and mutagenic essays. Food-grade silicon dioxide was neither mutagenic nor genotoxic in standard in vitro test systems. Standard oral in vivo genotoxicity tests were all negative (bone marrow micronucleus test, chromosome aberration test) (1).

In a study, the acute oral toxicity of precipitated silica was tested in male and female Wistar rats. Five rats per sex were gavaged with 5,100 mg/kg bw of the test substance suspended in vehicle. No clinical signs were detected during the 14-day post exposure observation period; the weight gain of rats was ‘normal’. No findings were reported at necropsy. In another study, no adverse effects were induced in rats and mice after chronic oral exposure up to 2,500 mg/kg bw per day in rats and up to 7,500 mg/kg bw per day in mice, the highest doses tested. The results indicated that silica was not carcinogenic (2). 

Silicon dioxide’s side effects and dangers

More study on the forms of silica that make their way into food items has been advocated for by some researchers. When it comes to particles smaller than most of those found in nature, nanoparticles are a good example.

The fear is that these microscopic particles might spread throughout the body and possibly enter cells.That is, because along with the improvement of the production process, the size of silica particles becomes smaller to a nanoscale. Now, silica nanoparticles are one of the most used nanomaterials in food. An increasing number of nanomaterials are present in food and the human exposure to these materials consequently increases, and hence may become a threat to the environment and the human body (3). 

Researchers in the Journal of Applied Toxicology studied the impact of silica nanoparticles as food additives. Silica nanoparticles were shown to have a minimal risk of passing through the digestive system when eaten. In this study, four silica nanoparticles (NP) samples were introduced to human gastric epithelial cell and colorectal adenocarcinoma cell to investigate the effect of silica sample, exposure dose and exposure period on the morphology, viability and membrane integrity of cells. The results indicate that all four silica NPs are safe for both cells after 24-h exposure at a concentration lower than 100 μgml–1. At a higher concentration and longer exposure period, silica NPs do not induce the apoptosis/necrosis of cells, but arrest cell cycle and inhibit cell growth and after the concentration reached to 200 μgml–1 and higher, silica NPs significantly affected the cell functions after 48-h exposure. These findings indicate that silica NPs could be used as a safe food additive, but more investigations, such as long-term in vivo exposure, are necessary in future studies (3).

There is no danger in utilizing silica nanoparticles as a food additive, according to the experts, but they advocated for greater long-term study. The EFSA has voiced concerns regarding the use of silica nanoparticles in food since there are no long-term safety studies to support their use. 

However, it is difficult to distinguish between nano and non-nano silica, and many producers are not explicitly mentioning that their goods include nanoparticles. So, whereas silica particles larger than nanometers seem to be safe for human consumption, there is insufficient evidence to support the same conclusion for nanoparticles. This can be explained by the fact that the silica nanoparticles could enter the animal body through different exposure pathways, distribute in nearly all organs and induce adverse effects in animals (3). 

So, as a result of this study, experts are calling for stronger regulations on the usage of silicon dioxide as a food ingredient.

Silicon dioxide adverse effect

Silica may have negative impacts. As a result, research on the dangers of silica tends to concentrate mostly on silica dust that is inhaled by humans. Inhaling silica dust over a long period may be dangerous, according to the ATSDR (Agency for Toxic Substances and Disease Registry). Workers in silica-processing plants and quarries are the most likely to experience this.

Long-term exposure to silica dust may cause a variety of respiratory problems, including:

·         Cancer

·         lung silicosis, a progressive and incurable lung illness

·         COPD (chronic obstructive pulmonary disease)

·         TB risk is raised

The kidneys may also be affected by long-term exposure to silica, increasing the risk of autoimmune disorders.

In addition, although no studies using these food additives have been performed to evaluate neurotoxicity or alterations in animal behavior, their non-food grade  nanosized counterparts have been associated with stress, depression, cognitive and eating disorders as signs of animal behavior alterations. It was identified that these food additives induce gastric toxicity, hepatotoxicity and alterations in gut microbiota and most evidence points out oxidative stress as the main mechanism of toxicity (4).


In this brief guide, we answered the query, “Is 551 vegan?’ and discussed the use and risks of E551.

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Fruijtier-Pölloth, C. The safety of nanostructured synthetic amorphous silica (SAS) as a food additive (E 551). Arch Toxicol, 2016, 90, 2885–2916.


EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS), et al. Re‐evaluation of silicon dioxide (E 551) as a food additive. EFSA Journal 2018, 16, e05088. 


Yang, Yi‐Xin, et al. Evaluation of the toxicity of food additive silica nanoparticles on gastrointestinal cells. J Appl Toxicol, 2014, 34, 424-435.