Silica: its beneficial effects on the hair.

What is silica?

The silica, or more precisely silicon, is a trace element naturally present in the environment and in the human body. It comprises silicon atoms bonded to oxygen (SiO₂) and is found in rocks, sand, plants, drinking water, as well as in certain foods such as whole grains, vegetables and beer. Within the body, silicon is largely located in connective tissues, skin, hair, nails, bones and cartilage, where it plays a vital structural role.

From a biological standpoint, silicon is involved in the synthesis of collagen (notably type I) and keratin, two essential proteins for the strength and quality of skin, hair and joint tissues. It thus contributes to the skin firmness, bone strength, as well as hair elasticity and vitality. However, not all forms of silica are equal in terms of absorption. Mineral forms such as colloidal or crystalline silica have very low bioavailability (less than 5% absorbed). In contrast, certain soluble and stabilised forms, such as orthosilicic acid stabilised by choline (ch-OSA) or monomethylsilanetriol (MMST), exhibit significantly higher bioavailability, ranging from 40 to 60%.

For example, a study published in 2008 in Nutrition & Metabolism showed that ch-OSA, administered at a rate of 10 mg of silicon per day, was well absorbed and excreted in the urine, confirming its assimilation by the body. Another study compared different forms of silicon and confirmed that ch-OSA and MMST were the most bioavailable, while colloidal silica was hardly absorbed.

There are currently no official daily intake recommendations for silicon dioxide, but average intakes in Western countries range between 20 and 50 mg per day. Dietary supplements generally supply between 5 and 10 mg of silicon in a bioavailable form, targeting beneficial effects on the skin, nails and hair. Finally, toxicological studies have demonstrated that the bioavailable silicon, particularly in the form of ch-OSA, is well tolerated and safe at the recommended doses. However, as with any supplement, it is advisable to consult a healthcare professional before commencing supplementation, especially if undergoing medical treatment or living with a chronic condition.

The benefits of silica for hair.

The silica (silicon dioxide in a bioavailable form) is increasingly used as an active ingredient in dietary supplements aimed at improving hair appearance. Several scientific studies support its beneficial effects, particularly with regard to hair fibre strength, elasticity and thickness. Polymerised forms, such as the silica colloidal or mineral, are very poorly absorbed by the body, unlike monomeric forms. Among the most extensively studied variants, choline-stabilised orthosilicic acid (ch-OSA) stands out for its good intestinal absorption and stability in solution.

A landmark, randomised, double-blind, placebo-controlled clinical trial was conducted in 48 women with fine hair. Over nine months, half of the participants received a daily 10 mg supplementation of silicon in the form of ch-OSA, while the other half received a placebo. The results demonstrated a significant improvement in several hair parameters in the treated group: the hair thickness (measured by fibre cross-sectional area) increased by 12.8%, compared to no notable change in the placebo group. Furthermore, the tensile strength (break load) was better preserved: a decrease of only 2.2% in the ch-OSA group versus 10.8% in the placebo group, representing a net gain of 13.1%. Moreover, the elasticity (measured by elastic modulus) decreased less in the supplemented group (−4.52% versus −11.9%), indicating greater retention of hair suppleness.

Another pilot study, involving 34 volunteers divided into three groups (placebo, M-OSA and MMST), demonstrated, after 150 days of supplementation, subjective improvements in hair texture, enhanced shine, and favourable effects on eyelashes and nails, although quantitative data were limited.

Despite these encouraging findings, certain limitations must be taken into account. The available studies are small-scale and often funded by supplement manufacturers, which may introduce bias.

Furthermore, the majority of observed benefits pertain to the quality of existing hair (strength, shine, thickness), with no solid evidence of an effect on regrowth or growth stimulation, and arising from oral supplementation rather than topical application.

The effect of silica is gradual: clinical studies show efficacy after several months of continuous supplementation (typically between five and nine months). Before starting a course, it is advisable to consult a healthcare professional, especially if you are taking medication or have chronic health conditions.

In which hair care products can silica be found?

The silica is an ingredient commonly used in hair care products, both in topical cosmetics and dietary supplements. It is sought after for its strengthening properties on the hair fibre, its ability to improve shine, limit breakage and, in certain cases, favour improved hair quality. It is found in various forms depending on the type of product, each offering specific effects.

In dietary supplements, the silica is present in bioavailable forms such as choline-stabilised orthosilicic acid (ch-OSA), scientifically recognised for its beneficial effects on hair thickness and strength. Other supplements also include silica derived from silicon-rich plants, such as bamboo extract or horsetail, often combined with other active agents like biotin, zinc or vitamin B8 to boost hair health. These products are typically offered as capsules, tablets or liquid solutions, to be taken over multi-month courses.

As far as cosmetic products, silica is incorporated into certain shampoos, conditioners, masks or styling sprays. It appears on the INCI list under the names “Silica”, “Hydrated Silica” or “Silica Silylate”. These forms, not absorbable by the skin, are used for their potential texturising properties: they would add volume, absorb excess sebum and improve the texture of hair care products. In some cases, silica also occurs in the form of natural powders, such as rhassoul (Moroccan clay) or Ayurvedic powders, which naturally contain silicon and are used to purify the scalp while strengthening the hair.