Silica — Research Profile

Choline-stabilized orthosilicic acid (ch-OSA, marketed as BioSil) is the best-studied and most bioavailable form. It provides silicon in a directly absorbable form. Horsetail extract is a traditional alternative but has variable silicon content and lower bioavailability. Colloidal silica (large particle) is poorly absorbed and not recommended.

The landmark Barel et al. study showed significant improvements in hair brittleness and nail hardness after 20 weeks (about 5 months) of daily ch-OSA supplementation. This timeframe aligns with hair and nail growth cycles. Expect to take silica consistently for at least 3-6 months before judging results.

Not exactly. Silicon (Si) is the element, while silica (SiO2, silicon dioxide) is the most common compound of silicon found in nature. In supplement form, orthosilicic acid [Si(OH)4] is the bioavailable species that the body can actually absorb and use. When people say "silica supplement," they typically mean a product providing bioavailable silicon.

The forms with actual human data are choline-stabilized orthosilicic acid (ch-OSA), used at 3-12 mg Si/day in bone trials, and monomethylsilanetriol (MMST) at about 10.5 mg/day. Orthosilicic acid itself is the most bioavailable form but is stable only in dilute liquid, and other forms are hydrolyzed to it in the gut. For skin, hair, and nail goals the strongest evidence is for ch-OSA, which decreased skin roughness and reduced nail and hair brittleness at 10 mg Si/day over 20 weeks.

The clearest human benefit is cosmetic: in a randomized, placebo-controlled trial, ch-OSA at 10 mg Si/day for 20 weeks decreased skin roughness and reduced nail and hair brittleness in women with photodamaged skin. For bone, a 12-month controlled trial of ch-OSA plus calcium and vitamin D produced modest femoral bone-density gains (greater than about 2% at the femoral neck at the 6 mg dose) and raised the collagen-formation marker PINP. Mechanistically, silicon stimulates type I collagen synthesis and osteoblast differentiation in vitro, but the trials are small and none has shown reduced fracture risk.

There is no RDA or Adequate Intake for silicon; typical diets provide about 19 mg/day in women and 40 mg/day in men, mostly from beverages, grains, and vegetables. Supplement trials used choline-stabilized orthosilicic acid at 3–12 mg elemental silicon/day (10 mg in the skin study, 6 mg in the bone study) and monomethylsilanetriol at about 10.5 mg/day^[1]. Around 25 mg Si/day has been suggested as adequate to support bone.

The best time of day to take silicon has not been directly studied. The human trials simply used a fixed once-daily dose - for example 10 mg Si/day of ch-OSA - without specifying or comparing any particular time of day. The published benefits rest on consistent daily intake rather than timing, so convenience and adherence are the practical priorities.

Oral silicon supplements are well tolerated: no tolerable upper intake level has been set because toxicity data are lacking, and silicon occurring naturally in food and water has no documented adverse effects. The only documented oral problem is rare silicate kidney stones - fewer than 30 cases, tied to years of magnesium-trisilicate antacid use rather than ordinary silicon supplements. Note that the serious harms associated with the word 'silica' come from inhaled crystalline silica dust in occupational settings, which penetrates deep into the lungs and is associated with elevated lung-cancer rates - an exposure unrelated to swallowing silicon in food or supplements.

No clinically significant medication interactions have been established for oral silicon or orthosilicic acid supplements. Silicon is not metabolized by the liver and is cleared renally, giving it little basis for the enzyme- or transport-based interactions seen with many supplements. People with advanced kidney disease clear silicon poorly — serum levels roughly double in renal failure — and should be cautious.

Silicon may appeal to people focused on skin, hair, and nail quality or on bone maintenance — the trial populations were women with photodamaged skin and adults studied for bone density ^[1][2]. Those with low intake of whole grains, mineral water, beer, and certain vegetables get the least dietary silicon, and intake also declines with age (about 0.1 mg less per additional year). It is not an established essential nutrient, and most people already obtain adequate amounts from a normal diet.

Silicon has no rapid effect. In the main cosmetic trial, choline-stabilized orthosilicic acid (ch-OSA) at 10 mg elemental silicon/day took 20 weeks to measurably decrease skin roughness and reduce nail and hair brittleness in women with photodamaged skin. Bone-related endpoints move even more slowly, with controlled ch-OSA trials tracking bone mineral density and the collagen-formation marker PINP over about 12 months. Expect a timescale of several months rather than days or weeks.

No tolerable upper intake level exists for silicon because there is no dose-response evidence of harm, and silicon occurring naturally in food and water has no documented adverse effects. Choline-stabilized orthosilicic acid at about 10 mg Si/day was used with no significant adverse effects for 20 weeks ^[1]. Multi-year safety of higher supplemental doses has not been formally characterized, though typical diets already supply roughly 19–40 mg/day without problems.

No upper limit has been set for silicon because toxicity data are lacking. The kidneys clear excess efficiently — up to roughly 50% of ingested silicon is excreted in urine — and an animal-derived safe upper level of about 1750 mg/day was estimated for a 70 kg adult, far above any supplement dose. The only documented oral problem is rare silicate kidney stones, seen in fewer than 30 people after years of heavy magnesium-trisilicate antacid use, not from ordinary silicon supplements.

Silicon is commonly paired with calcium and vitamin D for bone support; a 12-month trial gave 6 mg Si alongside calcium and vitamin D and saw small femoral bone-density gains. Because orthosilicic acid stimulates type I collagen synthesis in bone and connective-tissue cells, it is often taken with collagen or for skin and joint goals ^[3]. No negative interactions between silicon and other supplements have been documented.

Absorbability depends heavily on the form. Orthosilicic acid (OSA) is the most bioavailable form and other silicon forms are hydrolyzed to OSA in the gastrointestinal tract, but free OSA is stable only in dilute liquid, so the forms actually tested in humans are the stabilized ones: choline-stabilized orthosilicic acid (ch-OSA) and monomethylsilanetriol (MMST), both of which are well absorbed. Check the label for the elemental silicon content and favor one of these stabilized, water-soluble forms.