The element silicon (Si) and its oxidized compound, silica (silicon dioxide), are widely present in nature and are increasingly popular in supplements. The human body contains silicon in trace amounts, particularly in connective tissues. Silica supplements are marketed with claims of supporting beauty and structural health. This article clarifies the different forms of silica used in supplements and examines the scientific basis behind its purported health benefits.
Defining Silicon and Supplement Forms
Silicon is the elemental form, while silica (silicon dioxide) is the most common compound. Silica is generally insoluble in water and poorly absorbed by the body. For the body to utilize it, silica must be converted into a water-soluble form called orthosilicic acid (OSA). OSA is the biologically active molecule that is readily absorbed through the digestive tract.
The absorption of silicon varies significantly among supplement types. Highly absorbable forms include stabilized OSA, often complexed with choline (ChOSA) or monomethyl silanetriol (MMST). Plant-derived sources, such as horsetail and bamboo extract, are also common, but their absorption rates can be low because the silica is bound in complex structures. Colloidal silica, which consists of fine particles, has a particularly low absorption rate, sometimes as low as 1%.
Essential Role in Human Body Structure
Silicon is a naturally occurring trace element found in all healthy human tissues. Its concentration is highest in connective tissues like bone, skin, tendons, and the aorta. This element plays an established role in maintaining the body’s structural integrity.
The primary function of silicon involves the synthesis and stabilization of collagen, a foundational protein for connective tissues. It is believed to act as a biological cross-linking agent, helping to bridge proteoglycans and collagen fibers, which provides strength and flexibility. Silicon is also concentrated at the mineralization front of growing bone, suggesting a role in bone calcification and matrix formation. Evidence suggests that silicon levels decrease with age, leading researchers to investigate its role in age-related structural decline.
Supporting Claims for Hair, Skin, and Bones
The most frequent marketing claims for silica supplements revolve around enhancing the health and appearance of hair, skin, and nails. Since silicon is involved in collagen synthesis, it is theorized to improve skin elasticity and texture. Studies focused on sun-damaged skin have indicated that daily supplementation can lead to improvements in skin roughness and elasticity. This effect is attributed to the mineral’s influence on collagen production in the dermal layer.
For hair and nails, the claims center on increased strength, reduced brittleness, and greater thickness. Clinical studies have shown that silicon supplementation can result in stronger and thicker hair, particularly in women with fine hair. It is also linked to improving nail hardness and decreasing nail brittleness. Regarding bone health, observational research has found a positive association between higher dietary silicon intake and better bone mineral density in men and pre-menopausal women. This suggests silicon supports bone strength by facilitating the incorporation of calcium and magnesium into the bone matrix.
Dosage Guidelines and Safety Considerations
There is no official Recommended Daily Intake (RDI) for silicon. The average dietary intake in Western countries is estimated to be between 20 and 30 milligrams per day. Based on studies, an adequate intake to promote beneficial effects is often estimated to be in the range of 10 to 25 milligrams of silicon daily.
Oral ingestion of silica supplements at recommended doses is generally considered safe for most healthy adults. Because orthosilicic acid (OSA) is water-soluble, excess silicon is readily excreted through the urine. However, individuals with pre-existing kidney conditions should exercise caution. While rare, documented cases of silicate kidney stone formation (nephrolithiasis) have occurred in people taking high-dose or certain types of silica supplements. Anyone with kidney disease or a history of kidney stones should consult a healthcare provider before starting a silica supplement regimen.