Know2eat

Silica (silicon)

Minerals

What silica (silicon) may help with

Ranked by how strong the human evidence is — best supported first.

Best supportedHair growth and strengthLimited evidence· 4 sources

Then, in order

About Silica (silicon)

Silicon supplied as silica, as stabilised orthosilicic acid, or as plant extracts from bamboo or horsetail. It is sold almost entirely for hair, skin, nails and bone.

Silicon is present in connective tissue and there is a reasonable observational literature linking dietary silicon — mostly from beer, grains and drinking water — with bone density. Supplement evidence is much thinner: a small number of trials of choline-stabilised orthosilicic acid at 6–10 mg/day report effects on hair and nail measures and on bone turnover markers, with sample sizes in the tens and manufacturer involvement. Silicon has no established requirement and no upper limit, which reflects a lack of data rather than a clean bill of health. The horsetail-derived products carry an additional problem: horsetail contains thiaminase, which degrades thiamine.

Sold as
Capsule, Liquid orthosilicic acid, Bamboo extract, Horsetail extract, Gel
Standardised to
Trials used choline-stabilised orthosilicic acid standardised to elemental silicon — a product without this marker may not resemble what was studied.
Also known as
Silicon dioxide, Orthosilicic acid, ch-OSA, Bamboo silica, Horsetail silica

Regulation: No RDA, Adequate Intake or Tolerable Upper Intake Level has been established for silicon — EFSA concluded there was insufficient data to set one. Sold as a dietary supplement with no pre-market efficacy review. Silicon dioxide also appears widely as an anti-caking excipient, which is a different use at trivial absorbed amounts.

What the research used

The amounts, forms and durations published trials of Silica (silicon) actually administered.

These are the amounts published trials administered — not a recommendation, and not a dose to copy. Trial participants were screened, supervised and given a characterised preparation. What is in a retail bottle is frequently not what was studied, and the amount that suits one person is not general advice.

  • Studied for Hair, skin and nail trials

    5–10 mg

    Limited

    Choline-stabilised orthosilicic acid, daily · 20 weeks–1 year

    Small trials, generally fewer than 60 participants, using a branded ingredient with manufacturer involvement and largely subjective or instrument-based cosmetic endpoints.

  • Studied for Typical retail supplement

    5–40 mg

    Not enough

    Elemental silicon from various sources

    Bioavailability differs enormously between forms — orthosilicic acid is absorbed well, colloidal and plant silica poorly — so the elemental figure on the label says little about what is absorbed.

This is general information about food, not medical advice. It cannot diagnose, treat or replace guidance from a clinician who knows your history.

When it was taken

Each window says whether a trial compared it against an alternative, or whether it is convention and pharmacology. Most timing advice is the second kind.

None of the timings below were directly compared in a trial. They reflect how the research happened to dose, or what the pharmacology implies — which is not the same as a timing being better.

  • Any time

    Not enough

    No timing has been tested. Silicon absorption depends far more on the chemical form than on when it is taken.

    Timing was not directly compared. This reflects convention or how the compound behaves in the body, not a trial showing this window works better.

The evidence in depth

Best supported: Limited

What each association actually rests on, and the papers behind it. A rating describes the state of the research, not how promising the supplement sounds. How we rate evidence.

Hair growth and strength

Hair Health
Limited evidence

Small trials of stabilised orthosilicic acid report improvements in hair tensile strength and thickness in women with fine hair. The studies are small, industry-supported and have not been independently replicated.

Limited evidence. Early human work, or mostly lab and animal research.

View the 4 sources

Deep research mode adds each paper’s own conclusion and stated limitations.

Bone mineral density

Bone Health
Not enough evidence

Observational data associate higher dietary silicon with greater bone mineral density, particularly in men and premenopausal women. The trial evidence is limited to small studies measuring bone turnover markers rather than density or fractures.

Not enough evidence. Not enough human research to say anything useful yet.

View the 2 sources

Deep research mode adds each paper’s own conclusion and stated limitations.

Skin structure and hydration

Skin Health
Not enough evidence

One small trial reported improved skin roughness and elasticity measures over 20 weeks. Sample size was modest, the endpoints were instrument-based cosmetic measures, and the manufacturer was involved.

Not enough evidence. Not enough human research to say anything useful yet.

No source is attached to this association yet, so it is rated not enough evidenceby default. It is listed because people commonly ask about it — not because there is evidence for it.

Things to know

Interactions, contraindications and dose limits, most serious first. Concentrated extracts interact with medication in ways the whole plant does not, so this section carries more weight here than it does on a food page.

  • Worth knowing

    Horsetail-derived products contain thiaminase

    Horsetail contains an enzyme that degrades thiamine, and prolonged use has been linked to thiamine deficiency, particularly in people with heavy alcohol intake or poor diet. Products should state whether the enzyme has been inactivated, and many do not.

  • Worth knowing

    No upper limit and unknown long-term safety

    The absence of an upper limit reflects insufficient data. Trials run up to a year at low doses; long-term safety at the higher amounts some products supply has not been evaluated.

  • Worth knowing

    Kidney impairment

    Silicon is cleared by the kidneys, and silicon-containing compounds have been implicated in urinary stone formation in unusual circumstances. Supplementation is not advisable in significant kidney disease.

  • Worth knowing

    Bioavailability varies enormously between products

    Orthosilicic acid is absorbed reasonably well; colloidal silica and most plant silicas are not. The trials used one specific stabilised form, and results from it do not transfer to bamboo powder in a capsule.

In the food catalogue

The whole-food form, where one exists. The evidence for a concentrated extract rarely transfers to the food, or the other way round — these are cross-links, not equivalents.

BananaOne of the higher-silicon fruits, though absorption from it is low.BarleyA grain source, and the reason beer is a notable contributor in…Rolled oatsWhole grains are among the main dietary silicon sources.

Evidence ratings on this page: 1 limited evidence, 2 not enough evidence.

Supplements are sold in the US without pre-market review of efficacy or safety. Nothing on this page is a recommendation to take Silica (silicon), or a dose to follow.