silica

mineralSilica aerogel

What is it

Silica refers to silicon dioxide (SiO2), but in nutrition contexts often refers to silicon, the second most abundant element in the Earth's crust. Silicon in soluble forms (orthosilicic acid) is a trace nutrient present in the human body, with roles in connective tissue, bone, and cartilage.

How it works

Silicon is absorbed from the gut primarily as orthosilicic acid (Si(OH)4), the soluble form. Sources include drinking water, beer, certain plants (especially horsetail, oats, barley), and supplements. Most silicon in foods is bound in less absorbable forms; soluble forms are better absorbed. In the body, silicon contributes to the structure and integrity of connective tissues, including bone matrix, cartilage, skin, and blood vessels. It is thought to support collagen synthesis and the cross-linking of glycosaminoglycans. Research has explored silicon for bone mineral density, skin elasticity, hair and nail strength, and arterial health. Different silicon supplement forms vary in bioavailability. Choline-stabilized orthosilicic acid (ch-OSA) is one of the more bioavailable forms studied. Colloidal silica and silicon dioxide powder are less bioavailable. Silica from bamboo, horsetail, and similar plant sources is often poorly absorbed unless specifically processed.

Evidence for 4 uses

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Bone mineral density

Grade C

Moderate evidence

Some studies of choline-stabilized orthosilicic acid (ch-OSA) suggest modest benefits for bone density and turnover markers in postmenopausal women. Effects are modest and trial sizes have generally been small.

Skin elasticity and wrinkles

Grade C

Moderate evidence

Clinical trials of ch-OSA report modest improvements in skin surface and elasticity, particularly in older women with sun-damaged skin. Effects are gradual over months of use.

Hair and nail strength

Grade C

Moderate evidence

Some randomized trials suggest ch-OSA improves hair strength and reduces brittleness, and similarly improves nail quality, over several months of supplementation.

Cardiovascular health

Grade D

Mixed evidence

Epidemiological data suggest higher dietary silicon intake may be associated with reduced atherosclerosis, but interventional evidence is limited.

5 commercial forms

Choline-stabilized orthosilicic acid (ch-OSA)

Most bioavailable form; well-studied.

Stable liquid form of orthosilicic acid, used in most clinical research. Provides 5 to 10 mg of elemental silicon per dose.

Orthosilicic acid (OSA)

Bioavailable but unstable in solution.

The fundamental absorbable form. Unstable in solution, which is why stabilized forms like ch-OSA are used in supplements.

Silica from bamboo or horsetail

Often poorly absorbed unless specifically processed.

Plant-derived silica supplements. Most contain silicon dioxide that is poorly absorbed; some products process the silica into more bioavailable forms.

Colloidal silica

Suspension of small silica particles; bioavailability debated.

Liquid suspensions of fine silica particles. Marketing claims about bioavailability often exceed what evidence supports.

Silicon dioxide capsules

Generally poor bioavailability.

Common form in inexpensive supplements. The insoluble silica form is poorly absorbed without specific processing.

Dosage

There is no established RDA for silicon. Estimated typical dietary intake is 20 to 50 mg/day. Supplement doses range from 5 to 25 mg of elemental silicon daily, often in the form of orthosilicic acid or ch-OSA. No formal Tolerable Upper Intake Level has been established for silicon.

When and how to take it

Silicon is best absorbed in soluble forms (orthosilicic acid, ch-OSA) on an empty stomach with water. Insoluble silicon dioxide is poorly absorbed regardless of timing. Splitting doses between morning and evening can help maintain consistent silicon availability. No clear stimulant effect.

Food sources

Food	Amount	%DV
Beer	1 cup	—
Banana	1 medium	—
Whole grain bread	1 slice	—
Oats	1/2 cup dry	—
Green beans	1 cup	—
Mineral water (silica-rich)	1 cup	—
Brown rice	1 cup cooked	—

Safety

Soluble silicon supplements at typical doses are well tolerated. Side effects are uncommon and include mild gastrointestinal upset. Excessive intake of insoluble silica may cause constipation. Inhaled crystalline silica (industrial exposure) causes lung disease (silicosis) but this is not relevant to oral supplement use. Long-term safety of high-dose silicon supplements is not well established.

Who should be cautious

People with kidney disease should consult a clinician about silicon intake, as elimination depends on kidney function. Those on aluminum-containing antacids may have altered silicon and aluminum balance. Pregnant women can consume silicon at typical food levels but should consult a clinician about concentrated supplements.

Interactions

Silicon supplements have no major known drug interactions. They may modestly interact with magnesium or aluminum absorption. The bioavailability of silicon itself can be reduced by certain co-ingested compounds; orthosilicic acid is best absorbed on an empty stomach.

Frequently asked questions

Is silica an essential nutrient?⌄

Silicon (the elemental form of silica) is considered a possibly essential ultratrace nutrient. While the body contains and uses silicon, no human deficiency syndrome has been definitively established, and no RDA exists.

Which silica form is best absorbed?⌄

Soluble orthosilicic acid and its stabilized forms (choline-stabilized OSA) are best absorbed. Insoluble silicon dioxide and most plant-derived silica supplements are poorly absorbed unless specifically processed.

Does silica help with hair and nails?⌄

Some clinical trials of ch-OSA show modest improvements in hair and nail strength over months of use. Effects are gradual; magic claims about rapid hair growth are not supported.

Is silica from horsetail effective?⌄

Most horsetail-based silica is in insoluble forms that are poorly absorbed. Some manufacturers process horsetail to increase bioavailability; quality varies. Look for products with documented bioavailability data.

Can I get enough silica from food?⌄

Average dietary silicon intake (20 to 50 mg/day) is generally adequate. Beer, mineral water, whole grains, and certain vegetables are good sources. Supplementation may benefit specific applications like bone or skin support.

References

Silica (Wikidata) — Wikidata link
Silica (PubChem CID 24261) — PubChem link

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Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you're pregnant, breastfeeding, on medications, or managing a chronic condition.