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hydrated silica

Also known as: Silicon dioxide hydrate, SiO₂·nH₂O, Silica gel, Amorphous silica, Hydrated silica

Overview

Hydrated silica is a form of silicon dioxide that incorporates water molecules into its structure. It occurs naturally in forms like diatomaceous earth and is also synthetically produced for various applications. Primarily, it is utilized in oral care products such as toothpastes for its abrasive and polishing qualities, aiding in mechanical plaque and stain removal. Beyond dental applications, it serves as a thickening or anti-caking agent in cosmetics and pharmaceuticals. This compound is characterized by its amorphous, non-crystalline nature, which distinguishes it from crystalline silica and contributes to its generally low toxicity profile. It possesses a high surface area and adsorptive properties. While extensively studied for its safety, particularly regarding oral and dermal exposure, direct clinical evidence for its efficacy as a systemic dietary supplement is limited. Its primary recognized benefits are topical, with systemic absorption being minimal.

Benefits

The primary recognized benefit of hydrated silica is its role in dental care, where its abrasive properties effectively aid in mechanical plaque removal and enamel polishing. This is a direct, immediate benefit observed with topical application. There is no strong evidence from high-quality randomized controlled trials (RCTs) demonstrating direct systemic health benefits of hydrated silica when ingested as a supplement. While some research suggests that bioavailable silicon compounds may support bone health by contributing to collagen synthesis and bone mineralization, these findings are typically associated with soluble silicon forms rather than hydrated silica itself. Therefore, any hypothesized benefits for populations at risk of osteoporosis or bone fragility remain unproven for hydrated silica. No quantified effect sizes from RCTs on systemic health outcomes are available, and the time course of any potential systemic benefits is not established.

How it works

Hydrated silica primarily functions as a physical abrasive agent, particularly in oral care products, where it mechanically aids in the removal of plaque and stains from tooth surfaces. When ingested, hydrated silica exhibits very poor absorption within the gastrointestinal tract. It does not undergo significant chemical interactions within the body and is largely excreted unchanged. Studies on urinary excretion indicate that ingested silica peaks in urine within 48 hours and returns to baseline levels after approximately 8 days, confirming its limited systemic uptake and lack of significant accumulation in tissues. There are no specific molecular targets identified for hydrated silica acting as a systemic supplement, as its mechanism of action is predominantly physical and localized.

Side effects

Hydrated silica is generally recognized as safe (GRAS) for its intended uses in food, pharmaceuticals, and cosmetics at typical exposure levels. There are no common (greater than 5%) or uncommon (1-5%) side effects reported with its use. Rare side effects (less than 1%) are also not documented for hydrated silica. It is crucial to distinguish hydrated silica from crystalline silica; the latter, when inhaled as respirable dust, is associated with severe lung diseases like silicosis. However, hydrated silica, particularly in its oral or dermal forms, does not pose this inhalation risk. No significant drug interactions have been identified, and there are no established contraindications for its use. Special population considerations are minimal, though avoiding inhalation exposure to any silica dust is generally advised. Overall, its safety profile is robust, with extensive toxicological data supporting its non-carcinogenic and non-toxic nature at typical exposure levels.

Dosage

There is no established minimum effective dose or optimal dosage range for hydrated silica as a systemic supplement, primarily because its systemic health benefits are not conclusively demonstrated. Similarly, a maximum safe dose for systemic supplementation is not defined, though safety assessments indicate no toxic effects, carcinogenicity, or systemic toxicity with oral ingestion at typical exposure levels found in food and consumer products. Timing considerations are not applicable for systemic use. Hydrated silica is predominantly used topically in products like toothpastes and cosmetics. Oral supplementation is not a common practice. Its poor oral bioavailability significantly limits any potential systemic effects, meaning that even if ingested, most of the compound is excreted unchanged. No specific cofactors are identified as necessary for its action or absorption.

FAQs

Is hydrated silica safe to ingest?

Yes, hydrated silica is considered safe at levels used in food and oral care products, with no evidence of carcinogenicity or systemic toxicity reported in studies.

Does hydrated silica improve bone health?

There is no direct evidence from high-quality clinical trials supporting that hydrated silica improves bone health. Benefits are more associated with other bioavailable silicon compounds.

Can hydrated silica cause lung disease?

No, the risk of lung disease is linked to inhaling crystalline silica dust, not to hydrated silica used in oral care products or supplements.

How quickly is hydrated silica cleared from the body?

When ingested, urinary silica levels peak within 48 hours and return to baseline within approximately 8 days, indicating rapid clearance.

Research Sources

https://www.cir-safety.org/sites/default/files/Silica%20&%20Silicates.pdf – This comprehensive review by the Cosmetic Ingredient Review (CIR) panel concluded that hydrated silica is safe for use in cosmetics and oral care products. Animal studies showed no carcinogenic effects from oral ingestion, and human exposure levels are well below toxic thresholds. Urinary excretion studies demonstrated limited systemic absorption and clearance within days.
https://www.atsdr.cdc.gov/toxprofiles/tp211.pdf – This toxicological profile from the ATSDR summarized epidemiological and animal data, indicating that synthetic amorphous silica, including hydrated silica, does not cause adverse effects upon oral exposure. It clearly distinguishes hydrated silica from crystalline silica, which is associated with respiratory diseases, supporting the safety of hydrated silica in consumer products.
https://www.mdpi.com/2673-6373/4/4/38 – This scoping review highlighted the use of silica-based compounds in toothpastes for remineralization and oral health. While acknowledging hydrated silica's contribution to mechanical cleaning, it noted a lack of evidence for systemic health benefits from ingestion and identified gaps in clinical research regarding systemic effects of silica compounds.
https://cir-safety.org/sites/default/files/silica092019FR.pdf – This document, likely an updated or final report from the CIR, reiterates the safety of hydrated silica and silicates in cosmetic and oral care products. It reinforces findings of no carcinogenicity or systemic toxicity from oral exposure and confirms limited absorption and rapid excretion in humans.