Silica

Compound Class	Silicon dioxide (SiO2) in biogenic/phytolithic form — a mineral, not an organic phytochemical
Bioavailable Form	Orthosilicic acid (Si(OH)4) — the only form absorbed. Polymerised SiO2 is not
Botanical Sources	Equisetum arvense (horsetail; shavegrass) and Bambusa spp. (bamboo)
Plant Part(s)	Aerial stem (horsetail); stem/leaf (bamboo)
Typical Standardisation	Silica by gravimetric/ashing method; 7% from horsetail, 75% from bamboo
Primary Applications	Hair, skin, nail and connective-tissue formulation; bone-health positioning
Claim Strength (Overview)	Emerging — mechanistic plausibility is decent; the bioavailability question is the crux and is often ignored
Buy from Herbuno	Silica (75%) — from Bamboo → Silica 7% Powder (Horsetail Extract) | Standardized Equisetum arvense →

Name origin: Silica is silicon dioxide, and this monograph is unusual in the HerbIQ index because its subject is a mineral, not a phytochemical — the plant is merely a vehicle that has concentrated it. Equisetum derives from the Latin equus (horse) and seta (bristle), describing the plant’s appearance; horsetail is a living fossil, the sole surviving genus of a lineage whose ancestors reached thirty metres. Its silica content is what gave it the alternative name "scouring rush" — it was used to scrub pots. Traditional use: Horsetail dates back to Roman and Greek practice, used traditionally to stop bleeding, heal ulcers and wounds, and treat kidney complaints and tuberculosis. Bamboo has parallel uses in Asian traditions. Neither tradition identified silicon as the operative principle — that is a modern inference, and a reasonable one, but an inference nonetheless. Research trajectory: Modern interest turned on the observation that silicon is involved in connective-tissue and bone metabolism, and that its bioavailable form — orthosilicic acid — stimulates type I collagen synthesis in human osteoblast-like cells in vitro. The commercial hair-skin-nails category grew from that mechanistic foundation, considerably faster than the clinical evidence did. Safety context: Horsetail contains thiaminase, an enzyme that degrades thiamine (vitamin B1) — a documented and non-trivial caution discussed below.

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Evidence for Silica Applications

The bioavailability question is the crux of this entire category, and most marketing simply steps around it. Silicon is present in the diet in the bioavailable form of orthosilicic acid, and it is orthosilicic acid — not polymerised silica — that has been shown to stimulate osteoblastic cell differentiation and function; work examining orthosilicic acid’s effect on human osteoclasts found it inhibits osteoclast differentiation and bone resorption (Magnusson 2024 PLoS One). That is a coherent dual mechanism — stimulate bone formation, inhibit bone resorption. The problem is the delivery: highly polymerised silica has very limited solubility and must depolymerise to orthosilicic acid to be absorbed at all. Claim strength: Moderate (mechanistic, in vitro).

There is genuine human epidemiological support for silicon in bone, and it deserves recording. A cross-sectional population-based study of 1,251 men and 1,596 pre- and postmenopausal women in the Framingham Offspring cohort found that silicon intake correlated positively with adjusted bone mineral density at four hip sites in men and premenopausal women — though not in postmenopausal women — with differences in BMD of up to 10% between the highest (>40 mg Si/day) and lowest (<14 mg Si/day) intake quintiles (Jugdaohsingh 2004). This is observational rather than interventional, and the null in postmenopausal women — the group most at risk of osteoporosis — is a significant limitation that supplement copy routinely omits. Claim strength: Emerging.

The collagen mechanism, on which the hair-skin-nail category rests, is real but sits at a low evidence tier. Physiologic concentrations of orthosilicic acid have been shown to stimulate synthesis of type I collagen in human osteoblast-like cells in vitro, and the hypothesis is that by activating fibroblasts, orthosilicic acid induces a cytokine environment favourable to hair growth. Equisetum has separately been shown to inhibit 5-α-reductase in vitro, which would theoretically slow androgenetic alopecia. Both of these findings are explicitly in-vitro and mechanistic; neither is a demonstrated clinical outcome, and a supplier should say so. Claim strength: Emerging.

Horsetail versus bamboo is a real commercial choice with a real trade-off, and the higher number is not automatically the better ingredient. Horsetail contains roughly 5–8% silica in the dried herb (with standardized extracts around 7–10%), accumulated as biosilica or phytolithic silica; bamboo is far richer, and 75% silica extracts are commercially standard. But solubility and depolymerisation to orthosilicic acid, not total silica content, determine absorption. A 75% bamboo silica that is heavily polymerised may deliver less bioavailable silicon than a 7% horsetail extract — and neither supplier will typically have measured it. Claim strength: Moderate.

This leads to the specification question a formulator should actually ask, and almost nobody does: what is the soluble or orthosilicic-acid-releasing fraction? A gravimetric or ashing assay for total SiO₂ tells you how much silicon is present and nothing whatever about how much is absorbable. Choline-stabilised orthosilicic acid and other soluble silicon preparations exist precisely because this problem was recognised, and they carry human absorption data that plant-derived polymerised silica generally does not. This is not an argument against botanical silica; it is an argument for demanding the right number. Claim strength: High (established chemistry).

The thiaminase issue is a genuine, documented, and frequently omitted safety point rather than a theoretical one. The antithiamine action of Equisetum has been documented in the veterinary literature since the 1950s, where horsetail consumption produced thiamine-deficiency syndromes in livestock. The enzyme degrades thiamine (vitamin B1), and while heat treatment inactivates it, this cannot be assumed for a raw or minimally processed extract. Any horsetail product intended for prolonged use should either be certified thiaminase-inactivated or should carry appropriate caution — and buyers should ask, because most suppliers do not volunteer it. Claim strength: Moderate (documented adverse mechanism).

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Dosage & Formulator Specification

Herbuno carries Silica 75% from bamboo and Silica 7% from Equisetum arvense (horsetail), alongside a horsetail oil-soluble extract and bamboo leaf products. Buyers should understand that the higher silica percentage does not straightforwardly mean the better ingredient — solubility and orthosilicic acid release, not total SiO₂, determine absorption, and this figure is rarely measured by either supplier or buyer.

Dosing guidance for botanical silica is honestly constrained by the bioavailability problem: because absorption depends on depolymerisation to orthosilicic acid rather than on total silica content, a serving size expressed in milligrams of SiO₂ is not a meaningful measure of delivered silicon. Human absorption studies exist for soluble silicon preparations such as choline-stabilised orthosilicic acid, and those figures cannot simply be transferred to a polymerised botanical silica. Formulators should be candid in label copy about supplying silica rather than implying a validated silicon delivery, and should not scale dose upward on the assumption of proportional absorption.

Analytical verification should specify total silica by gravimetric or ashing method — and then, crucially, should go further and request the soluble or orthosilicic-acid-releasing fraction, which is the number that actually predicts absorption and which almost no specification sheet reports. Ask for it anyway. Botanical source and species must be documented (Equisetum arvense, not the toxic E. palustre, which contains the alkaloid palustrine and is a documented adulterant of horsetail material). For horsetail, thiaminase status — whether the enzyme has been heat-inactivated — should be specified. Heavy-metal testing is appropriate given that silica-accumulating plants can concentrate other minerals.

Silica from food sources is well tolerated and silicon has no established toxicity at dietary intakes. Three cautions apply specifically to horsetail and warrant clear statement. First, thiaminase: Equisetum contains an enzyme that degrades thiamine, documented since the 1950s veterinary literature as producing B1-deficiency in livestock, making prolonged use of non-heat-treated horsetail a genuine concern — particularly in individuals with existing thiamine insufficiency, including those with high alcohol intake. Second, species adulteration: Equisetum palustre contains the toxic alkaloid palustrine and is a documented adulterant; botanical authentication is essential, not optional. Third, horsetail has traditional diuretic use, so caution is appropriate alongside diuretic medication and in individuals with kidney disease. Bamboo silica does not carry the thiaminase concern.

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Frequently Asked Questions — Silica

Does the silica percentage tell you how much silicon you absorb?
No, and this is the crux of the category. Only orthosilicic acid is absorbed; polymerised silica must depolymerise first, and highly polymerised silica has very limited solubility. A gravimetric assay for total SiO2 tells you how much is present and nothing about how much is absorbable. A 75% bamboo silica may deliver less bioavailable silicon than a 7% horsetail extract.

Is bamboo silica better than horsetail silica?
Not necessarily, despite the far higher number. Bamboo commonly assays at 75% versus horsetail's 7-10%, but solubility and orthosilicic acid release — not total silica — determine absorption, and neither supplier typically measures it. Ask for the soluble fraction. Bamboo does, however, avoid horsetail's thiaminase issue.

What is the thiaminase concern with horsetail?
It is real and frequently omitted. Equisetum contains thiaminase, an enzyme that degrades thiamine (vitamin B1), documented since 1950s veterinary literature as producing B1-deficiency syndromes in livestock. Heat treatment inactivates it, but that cannot be assumed for raw or minimally processed extract. Prolonged use warrants caution, especially with existing thiamine insufficiency.

Does silica actually help hair, skin, and nails?
The mechanism is plausible but the evidence tier is low. Orthosilicic acid stimulates type I collagen synthesis in human osteoblast-like cells in vitro, and Equisetum inhibits 5-alpha-reductase in vitro. Both are in-vitro mechanistic findings, not demonstrated clinical outcomes — and both concern orthosilicic acid, which returns you to the bioavailability problem.

Related compounds: Betaine, Polyphenols, Flavonoids, Quercetin

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Claim-strength scale – High = multiple human RCTs; Moderate = limited trials or strong preclinical convergence; Emerging = early-stage lab or animal data.

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