Horsetail, Silica and Connective Tissue: Tradition Meets Thin Evidence
Horsetail (Equisetum arvense) is the odd one out in most skin formulas — a botanical among vitamins and minerals. It's an ancient plant, a survivor from a lineage that predates flowering plants entirely, and it has an unusual chemical feature that explains its presence.
Why horsetail
Horsetail accumulates silica from the soil to a degree almost no other plant matches — up to a substantial fraction of its dry weight. That silica is what makes the stems abrasive enough that they were historically used to scour pots and polish wood, which is where the old name "scouring rush" comes from.
Silicon is the third most abundant trace element in the human body, and it concentrates in connective tissues: skin, bone, cartilage, hair and nails. That distribution is the whole rationale.
What silicon appears to do
The proposed mechanism is collagen cross-linking. Silicon appears to be involved in the enzyme prolyl hydroxylase — the same enzyme system vitamin C supports — and in forming the cross-links between collagen and glycosaminoglycans that give connective tissue its structure and resilience.
Supporting this, animals fed silicon-deficient diets develop abnormal connective tissue and skeletal deformities. And human observational work has found associations between dietary silicon intake and bone mineral density.
It's a coherent story. The issue is what comes next.
Where it gets thin
Silicon is not classified as an essential nutrient for humans. No recommended intake has been established, no deficiency syndrome has been described in people, and the evidence base is dominated by animal studies and observational associations rather than controlled human trials.
A small number of trials have examined silicon compounds — usually choline-stabilised orthosilicic acid rather than horsetail extract — for skin, hair and nail quality, and reported modest improvements in measures like skin roughness and nail brittleness. These were small, and they used a specific bioavailable silicon compound, not a herb.
That distinction matters. The silica in horsetail is largely in polymerised forms with limited absorption. Demonstrating that a highly bioavailable silicon supplement does something is not the same as demonstrating that horsetail extract does.
Safety — the part worth reading
Horsetail has two specific considerations that set it apart from the vitamins alongside it.
Thiaminase. The raw plant contains an enzyme that breaks down thiamine (vitamin B1). Prolonged use has been associated with thiamine depletion, and this is well documented in livestock that graze on it. Preparations intended for human use are generally treated to inactivate the enzyme, but it's the main reason horsetail isn't recommended for long uninterrupted use.
Diuretic effect. Horsetail increases urine output — in fact that's its most established traditional use. This means it can interact with prescription diuretics and with lithium, whose blood levels depend on kidney handling and can rise dangerously if fluid balance shifts. Anyone taking either should not take horsetail without medical advice.
It's also not recommended in pregnancy or breastfeeding, and people with kidney disease should avoid it. Correct species identification matters too, as some related Equisetum species carry higher alkaloid content.
The bottom line
Horsetail is a reasonable traditional inclusion with a plausible mechanism and genuinely limited human evidence for skin specifically. It's the ingredient in this kind of formula we'd put the least weight on, and the one with the most specific cautions attached. If you take a diuretic or lithium, that's a conversation with your doctor before you start, not after.
References
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Horsetail extract is VitaRenova's one botanical
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Check Current Pricing →This article discusses a nutrient or approach in general, not VitaRenova as a finished product. Research on a single ingredient at a studied dose does not tell you what any particular gummy will do — check the supplement facts panel on the bottle you receive. Nothing here is medical advice; speak to a qualified healthcare professional before starting any supplement.