Introduction
Silica, also known as silicon, is a mineral often referred to as a trace element in nutrition. It is the third most abundant trace element in the human body, although it is not officially classified as an essential nutrient. Nevertheless, growing research shows that silica may play important roles in various aspects of health, particularly related to bones, connective tissue, skin, hair, and nails. In this article, we explore what science says about silica: its functions, bioavailability, interaction with other minerals, dietary sources, and safe doses to support overall health.
Silica in the body and bioavailabilityWhat is silica? Silica usually refers to silicon dioxide or other silicon-containing compounds. In a biological context, silicon often occurs as soluble orthosilicic acid, especially in liquids such as water and body fluids. The body contains silicon in small amounts, particularly in tissues such as bone and connective tissue.
Bioavailability, or absorption, is an important factor in silica’s effect in the body. Silica exists in various chemical forms, and how easily it is absorbed varies significantly depending on the form. Monomeric orthosilicic acid is absorbed most efficiently, with a bioavailability that can reach up to 50%. Polymerized forms, such as silica gel, colloidal silica, or silica particles from plants, on the other hand, often have very low absorption, sometimes below 1%.In general, the more bound or polymerized silicon is, the more poorly it is absorbed. For example, silica in drinking water and beer is mainly in the form of orthosilicic acid and is therefore readily available to the body, whereas silicon bound in fiber-rich plant foods, such as banana, may have an absorption rate of under 2%.
Silica and bone health
One of the most studied areas for silica is its role in the skeleton. As early as the 1970s, animal studies showed that silicon is involved in normal bone development. Animals on a low-silicon diet developed deformities in bones and cartilage, while silicon supplementation promoted bone growth, collagen formation, and calcium deposition in bone tissue. More than 30 years of research has provided strong indications that dietary silicon may contribute positively to bone mineralization and the health of connective tissue.
Bone mineral density and strength are central aspects of bone health. Epidemiological studies have found a clear association between higher silica intake and better bone mineral density. In both the USA and the UK, individuals with higher dietary silica intake have shown higher bone density, particularly among men and premenopausal women. This suggests that silica may support strong bones. Mechanistic research shows that silica is present at the active mineralization front in growing bone, indicating a role in the early calcification of the bone matrix. Silicon can bind to components in bone tissue and promote the deposition of calcium and other minerals in the skeleton. Furthermore, silica is involved in the synthesis and stabilization of collagen, the most important protein in the bone matrix and cartilage. Without sufficient collagen, the minerals cannot form a solid structure, so silica’s influence on collagen may be crucial for bone strength.
In a study of postmenopausal women with a tendency toward brittle bones, silicon supplementation was given together with calcium and vitamin D. The group that received additional silicon experienced a significant increase in bone density in the femoral neck compared with the control group. This suggests a synergistic effect in which silica, in the presence of calcium and vitamin D, may support new bone formation or reduce bone loss. At the same time, other studies have not always shown major changes in bone mineral content with silica supplementation when the diet is already sufficient. Animal studies have shown that additional silicon can increase the calcium content of bone only if the diet was originally low in calcium. If calcium intake is sufficient, silicon alone does not appear to provide extra minerals to the bones. Nevertheless, there are indications that silica may support both bone mineral density and bone strength through effects on mineral metabolism and the collagen network.
Silica and connective tissue (collagen and cartilage)
Connective tissue includes the body’s supporting tissues, such as cartilage, tendons, ligaments, and other tissues that contain collagen and proteoglycans. Silica appears to be important for the maintenance of such tissue. Connective tissue-rich structures, such as artery walls, the trachea, and cartilage, contain particularly high concentrations of silicon. This is believed to be due to silica’s role in the formation of glycosaminoglycans and proteoglycans, complex molecules that make up much of the ground substance in connective tissue. Silicon can be integrated into these structures and contribute to cross-linking between proteoglycan complexes and collagen fibers, which increases tissue strength and reduces permeability in the connective tissue matrix. Put simply, silica may help bind together the components of connective tissue to make it stronger and more resilient.
Collagen synthesis is a central process in connective tissue, and collagen is the dominant protein in skin, tendons, and cartilage. Silica is believed to support collagen formation. Studies have shown that silicon can stimulate fibroblasts, connective tissue cells that produce type I collagen. It has also been proposed that silica helps activate enzymes involved in the hydroxylation of collagen, a chemical modification that is important for the maturation and stabilization of collagen fibers. Without sufficient silicon, these enzymes may be less effective, which could potentially lead to a weaker collagen structure. In animal studies, silicon deficiency has been linked to reduced collagen content in bone and cartilage, while supplementation significantly increased collagen levels. This supports the idea that silica has an important function in collagen biosynthesis or stabilization.
Cartilage and joints depend on a durable yet flexible matrix of collagen and proteoglycans. Given silica’s role in both of these components, adequate silicon may contribute to healthy joints. Animal research has shown that a silicon-deficient diet led to abnormal cartilage development.Wound healing is another process in which connective tissue regeneration is crucial. Collagen deposition is key when wounds in the skin or other tissue are healing. Silica’s effect on collagen and tissue formation suggests that it may support wound healing. Clinical research on this is limited, but some reports have highlighted silicon’s potential role in promoting wound healing and connective tissue repair. This may be related to cells having sufficient building blocks and cofactors, such as silica, to form new tissue efficiently. More research is needed to confirm how much silica may influence wound healing in humans, but the biological plausibility is present.
Silica for skin, hair, and nailsSilica is well known among supplement enthusiasts for its presumed effect on skin, hair, and nails, all of which consist of strong protein networks – collagen in skin and keratin in hair and nails. These tissues are considered skin appendages, and silicon has been shown to be present in significant concentrations in hair and nails, where it is a dominant mineral in the composition of nails. Many people experience brittle nails and lifeless hair as signs of nutritional deficiencies, and some experts have suggested that soft or brittle nails may indicate a systemic silicon deficiency.
Skin elasticity and anti-aging are influenced by collagen and elastin, which provide structure and resilience. With age, these fibers gradually break down, and the skin becomes thinner and less elastic. Silica may support new collagen synthesis and slow this breakdown by contributing to very good activity of enzymes that are necessary to form and maintain collagen in the skin. In a placebo-controlled study of 50 middle-aged women with sun-damaged skin, the participants received two capsules daily, each containing stabilized orthosilicic acid equivalent to 10 mg silicon per capsule, for 20 weeks. After the period, a significant improvement in the skin surface microstructure was observed r and mechanical properties, such as elasticity, in the silicon group. The skin’s appearance, measured by roughness index and elasticity, improved, while the placebo group showed no corresponding change. This was the first double-blind, controlled study to document such effects of silica supplementation, and it suggests that silica may have cosmetic and dermatological benefits for aging skin.
Hair growth and hair strength are influenced by keratin, the main protein in hair, but also by minerals such as silicon found in the hair strands. Higher silicon content in a hair strand is associated with a lower risk of breakage and possibly less hair loss. Silicon may contribute indirectly by transporting nutrients to the hair follicles and by binding to amino acids or keratin to strengthen the structure. In one study, 48 people with thin, brittle hair took a stabilized orthosilicic acid supplement daily for 9 months, corresponding to 10 mg of pure silicon per day. At the end of the trial, the hair of those who received silicon had significantly higher breaking strength and thicker hair strands, while the placebo group showed no improvement. This suggests that long-term silica supplementation may result in stronger, fuller hair, possibly by being integrated into the hair fibers or stimulating the production of hair proteins. The researchers speculated that silica may interact with the keratin structure via silanol groups that form complexes with the proteins.
Potential effects on cognitive function
Can silica affect the brain and nervous system? This is less explored than bone and skin health, but there are interesting observations. Silicon is not known as a critical nutrient for the function of nerve cells, but it may indirectly affect the brain through other mechanisms, especially through interaction with metal ions such as aluminum.
Silica, aluminum, and cognitive health are an area of interest. Aluminum has long been suspected of having a role in neurodegenerative processes, although the connection has not been definitively proven. Silicon appears to be able to counteract aluminum by binding to it and forming insoluble aluminum silicates in the gastrointestinal tract, which may prevent absorption in the body. This may function as a natural way to reduce potential negative effects of aluminum. A large French cohort study followed nearly 2000 older individuals over 15 years and examined mineral intake via drinking water in relation to cognitive health. They found that those who consumed more silicon from drinking water had a lower risk of cognitive challenges – an increase of 10 mg of silicon per day was associated with an approximately 11% reduced risk. Conversely, higher aluminum intake was linked to increased risk. These findings suggest that silica may have a protective effect on the brain, possibly by preventing aluminum from accumulating in brain tissue. Small studies have shown that people who drank silicon-rich mineral water over time had reduced aluminum levels in the body and trends toward improved cognitive function in some individuals. However, the evidence base is still limited, and silica cannot be recommended for the prevention or treatment of cognitive challenges. A moderate silicon intake through diet and water is likely beneficial for general health and may have positive side effects on the brain by helping to reduce potentially harmful substances such as aluminum.Potential effects on the immune system
The link between silica and the immune system is complex. Inhalation of silica particles, such as stone dust, can overstimulate the immune system in the lungs and lead to harmful effects, but this applies to crystalline silica that is inhaled, not supplements or dietary silicon. The question is whether silica in supplements has immune-supporting or immunoregulatory properties.
There is limited research directly in humans examining silica supplements and immune function, but animal studies provide some indications. In a model of induced joint inflammation in animals, silicon supplementation was found to dampen the autoimmune response, suggesting that silica may enhance anti-inflammatory responses and modify immune reactions in a favorable direction during chronic inflammation. A reduction in the number of circulating lymphocytes during inflammation was also observed in the animals that received silica, which may be interpreted as a dampening of excessive immune activity.At a general level, some sources have suggested that silicon may support the immune and hormonal systems and help maintain a balanced pH in the body, which in theory could create a less favorable environment for pathogens. These statements often stem from laboratory or animal studies, or holistic perspectives, rather than large clinical trials. Indirectly, silica may support the immune system by helping maintain healthy mucous membranes and skin, which are the body’s first line of defense against infections. Adequate silicon intake may contribute to stronger connective tissue in the skin and mucous membranes and thereby improved barrier function. This is a logical implication rather than something directly measured, but robust tissue may help prevent bacteria and viruses from penetrating the body’s defenses.
In summary, there may be immune-related benefits of silica, especially linked to its potential anti-inflammatory properties. Boron, another trace mineral, is better known for influencing immune response and inflammation, and it is possible that silicon has similar, milder effects. For now, we lack clinical studies showing that healthy people gain a stronger immune system from silica supplements, so such claims should be made cautiously.
Interaction with other minerals: boron, calcium and magnesium
Minerals in the body rarely act alone; they are part of complex networks in which they can enhance or inhibit each other’s absorption and functions. Silica has interesting interactions with several minerals, especially those that have overlapping roles in bone health.
Calcium interacts with silica both in the intestine and in bone tissue. High levels of calcium in the diet can potentially reduce the absorption of silicon, possibly by forming complexes that are difficult to absorb, while low calcium may increase silicon absorption. In the skeleton, they work together: calcium is the main mineral in the hydroxyapatite crystals that make bone hard, while silica likely helps these crystals be deposited efficiently in the collagen matrix. Some researchers have suggested that silica may influence how calcium and magnesium are transported or used in the body. The amount of silicon excreted in the urine often correlates with calcium excretion, which may indicate that they follow some of the same metabolic pathways. In practical terms, this means that silica supplementation for bone health should be combined with an adequate intake of calcium and vitamin D for very good effect, as shown in studies in which silicon has demonstrated positive results on bone density.
Magnesium is another key mineral for the skeleton and connective tissue. Silica and magnesium can affect each other in ways similar to silica and calcium. Animal studies have shown that silicon supplementation sometimes lowers magnesium concentration in serum or increases magnesium excretion, but this did not lead to less magnesium in bone tissue – bone magnesium remained stable. This may involve complex buffering or distribution mechanisms. Both magnesium and silicon are involved in enzymatic processes linked to collagen synthesis and bone growth, so they may have complementary roles. If silica supplementation is being considered, sufficient magnesium intake should also be ensured, as very good bone and connective tissue health depends on both.
Boron is a trace element that, like silicon, is not officially recognized as essential, but has clear effects on bones and hormones. Boron and silica are often found together in plant foods such as fruits and vegetables and are both associated with bone health. Boron can positively influence the metabolism of calcium, magnesium, and vitamin D by reducing the excretion of calcium and magnesium and increasing the activation of vitamin D, which in turn benefits the skeleton. Silica and boron may therefore support the skeleton through somewhat different mechanisms: boron regulates mineral balance, while silica contributes to the structure. Both promote bone growth in animal models, and deficiency of either can lead to weakened bones in experimental animals. Although direct interactions between boron and silicon have not been extensively explored, it is logical that a diet that supports bone health includes sufficient amounts of both of these trace elements, together with calcium, magnesium, and vitamins such as D and K.
In summary, silica works together with calcium and magnesium by supporting their integration into bone and connective tissue, and may hinder the absorption of potentially undesirable minerals such as aluminum. Boron and silica complement each other by strengthening bone – boron helps mineral metabolism, while silica contributes to the physical structure. Balance is the key to holistic health, and a varied diet will usually provide these micronutrients in sufficient amounts. In cases where the intake of plants or water is low, such as in vegans with little processed grain or individuals with limited access to mineral-rich water, silica intake may be lower, and supplementation may be considered.
Silica is found in a range of common foods and beverages. Plants generally contain more silicon than animal products, as they absorb silicon from the soil and incorporate it into their structures. Here are some important sources:
Whole grains and cereal products are among the richest sources of silica. Oats, barley, millet, and brown rice in particular have a high silicon content. Refined grains lose some silica because it is found in the bran and fiber. A typical whole-grain breakfast cereal may contain around 5–20 mg of silicon per 100 g. In many Western diets, 30–50% of silicon intake comes from cereal products, and in Finland, grains account for about 68% of children's silicon intake.
Vegetables and legumes also contribute, especially those with edible skins or roots that may contain soil particles. Root vegetables may contain silica from the soil they grow in, but it is recommended to wash them well, even though a small amount of soil residue may increase silicon intake. Certain types of beans, such as green beans, have a relatively high silicon content, with analyses showing up to about 8 mg per 100 g. Leafy greens and other common vegetables have lower levels, but all contribute a little.
Fruit generally contains little silica, with the exception of bananas, as well as dried fruits such as apricots, dates, and raisins, and nuts. A medium-sized banana may contain around 5 mg of silicon, but the bioavailability is low, below 2%, so the practical benefit is limited. Dried fruit and nuts may have more concentrated levels of silica because the water has been removed, but the amount consumed is often small.
Herbs and specialty plants such as horsetail, also called equisetum, are known for their extremely high silica content and have traditionally been used as a source of silicic acid. Other plants in the grass family, such as bamboo shoots and sugarcane, also accumulate silicon. Some supplements are extracted from bamboo extract or horsetail, as they may naturally contain 5–10% silicon by dry weight.
Drinking water is a significant source of silica, depending on the geology of the area. Silicon in water occurs as dissolved orthosilicic acid, which is very easily absorbed. In countries with mineral-rich water, it may contribute several milligrams per liter, while levels are lower in areas with soft water. European mineral waters vary from about 4 mg/L up to 16 mg/L silicon, and some commercial waters may contain as much as 30–40 mg/L, which has been used in studies to reduce aluminum in the body. In general, drinking water and other beverages may account for 20% or more of daily silicon intake.
Beer is a surprisingly good source of silica for many adults. Barley malt and hops release silicon during brewing, and beer contains orthosilicic acid at concentrations of about 5–20 mg per liter, depending on the type. Studies have shown that beer drinkers, especially men, may have significantly higher silicon intake than non-drinkers; in Finland, 44% of men's silicon intake came from beer. Silicon from beer is also absorbed efficiently, as shown by high urinary excretion levels after consumption. This is not an encouragement to increase alcohol consumption, but it illustrates how dietary habits affect silicon levels. Non-alcoholic beer or malt extracts could theoretically provide similar benefits without alcohol.
A diet rich in whole grains (preferably not wheat), vegetables, beans, and mineral water automatically provides some silica. In Western countries, average intake is estimated to be 20–50 mg of silicon per day, twice as much as the typical intake of iron or zinc, even though silicon receives less attention. In plant-based diets, such as in India and China, intake may reach 140–200 mg/day, while it may be lower than 20 mg in groups with little plant intake or limited water consumption.
Recommended intake and dosage for health benefits
There is no official recommended daily intake (RDI) for silica in Norway, the EU, or the USA, but an adequate intake is estimated at 10–25 mg per day for adults. Most people get this through their diet, with an average of 20–30 mg/day in Western countries.
Silica is found in multivitamins and supplements for skin, hair, and nails, often in doses ranging from 5–25 mg per day. Studies show that 10 mg daily may have positive effects on skin and hair, while 20–30 mg per day, together with calcium and vitamin D, may support bone health. Higher doses (40–50 mg/day) have not shown clearly better effects, as the body does not absorb unlimited amounts.
Silica supplements are considered safe in moderate doses. A 20-week study using 20 mg/day reported no side effects. Excess is efficiently excreted in the urine, but very high doses may theoretically place a burden on the kidneys. EFSA considers silicon dioxide safe in normal amounts, but extreme doses should be avoided.
For general health, including skin, hair, and nails, 5–10 mg per day is recommended. For bone health, 10–20 mg per day may be considered, especially together with calcium and vitamin D. Start with a low dose and consult a doctor if you have medical conditions or use diuretic medications. Silica supplements should supplement, not replace, a balanced diet.
Concluding remarksSilica appears to be an exciting trace element with many biological connections. Although it has long been underestimated, modern research suggests that silicon has important supportive functions in the body – from contributing to strong bone structure and healthy connective tissue to supporting beauty-related aspects such as the skin’s youthful appearance and hair strength. There are also promising links to cognitive health and immune balance, mainly indirectly through mechanisms such as aluminum detoxification and anti-inflammatory effects.
For specific goals, such as strengthening hair and nails, a supplement may be considered in consultation with a healthcare professional, with sensible doses and realistic expectations. As with all supplements, it is important to follow guidelines and avoid unrealistic claims. Silica is not a miracle cure, but it is undoubtedly a contributing factor in the body’s intricate biochemistry for keeping bones strong, connective tissue supple, and external attributes healthy. Continued research will hopefully provide better insight into how this mineral can promote health in a safe and effective way.
- Silicon and bone health
- The role of silicon in connective tissue health
- Silicon and its role in bone formation
- The biological role of boron in humans: A review
- Boron and its role in nutrition and health: A review
- Boron: A key element in bone health, calcium metabolism, and prevention of arthritis
- Nutritional Bioavailability of Silicon
- Effect of oral intake of choline-stabilized orthosilicic acid on hair tensile strength and morphology in women with fine hair
- Effect of oral intake of choline-stabilized orthosilicic acid on skin, nails and hair in women with photodamaged skin
- Silicon supplementation and bone health: A review of the evidence
- Dietary silicon intake is positively associated with bone mineral density in men and premenopausal women of the Framingham Offspring cohort
- Silicon intake and Alzheimer's disease: Results from the PAQUID cohort
