Alternate Title

  • Silicon dioxide

Related Terms

  • Aluminum silicate, amorphous silica, attapulgite, bentonite, calcium silicate, crystalline silica, diatomite, fuller’s earth, hectorite, kaolin, lithium magnesium silicate, lithium magnesium sodium silicate, magnesium aluminum silicate, magnesium silicate, magnesium trisilicate, monomeric silicic acid, monosilicic acid, montmorillonite, orthosilicic acid, pyrophyllite, quartz, SiO2, Si(OH)4, silicate, silicic acid, sodium magnesium silicate, zeolite, zirconium silicate
  • Note: This monograph does not cover silicon-based manufactured materials, including microelectronics and biomedical devices and materials.


  • Silicon is the second-most abundant element in the earth’s crust, after oxygen. It binds to oxygen, forming crystalline or amorphous silica (silicon dioxide, SiO2), silicic acid (Si(OH)4), and silicates, such as quartz. Silicon is present in rocks, soil, sand, and dust as crystalline silica. Silicic acid is formed naturally from silica and is readily absorbed in the human gastrointestinal tract.
  • Silicon is an ultratrace element, meaning that it is suspected as being required in quantities of less than 1 milligram, but is associated with no known essential role in biological processes. A recommended dietary allowance (RDA) or adequate intake (AI) has not been established for silicon.
  • In the diet, silicon is found mainly in drinking water and plant-based foods, such as beer, unrefined grains (oats, barley, rice, and wheat bran), fruits, vegetables (spinach), and beans (red lentils).
  • Silicon is included as silicates in cosmetic and pharmaceutical preparations. Silicates are also added to processed foods and beverages, where they serve as anticaking agents, thickeners, and stabilizers, and they are used as clarifying agents in beer and wine.
  • Silicon is biocompatible and has been used in many implantable medical devices, including pacemakers, defibrillators, stents, materials for plastic and reconstructive surgery (including breast implants and bone grafts), devices for sustained-release delivery of drugs, sheeting (to treat and prevent the formation of scars following surgery), and liner sockets, or sleeves (to attach prostheses after amputation).
  • Although researchers have examined the use of silicon for various purposes, its use for reducing aluminum toxicity associated with Alzheimer’s disease is controversial. Some evidence suggests that silicon may be essential in humans for bone growth and health and development of other tissues in the body. High-quality scientific evidence supporting the use of silicon to treat any condition in humans is lacking.

Evidence Table


    These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

    Alzheimer’s dementia

    Preliminary studies suggest that dietary silicon supplementation may reduce aluminum absorption and prevent or reduce aluminum accumulation in tissues. It has been proposed that this may be useful in preventing or reducing aluminum accumulation in the brain in Alzheimer’s disease. Additional research is needed before a conclusion can be made.

    Brittle fingernails

    Daily doses of 10 milligrams of silicon or 10 milliliters of colloidal silica have been used effectively to treat brittle nail syndrome. Additional research is required in this area.

    Growth (bone health and development)

    Evidence suggests that silicon is involved in bone and collagen mineralization. Limited studies have demonstrated an association between silicon intake and bone mineral density.

*Key to grades:



    The below uses are based on tradition, scientific theories, or limited research. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. There may be other proposed uses that are not listed below.



    The below doses are based on scientific research, publications, traditional use, or expert opinion. Many herbs and supplements have not been thoroughly tested, and safety and effectiveness may not be proven. Brands may be made differently, with variable ingredients, even within the same brand. The below doses may not apply to all products. You should read product labels, and discuss doses with a qualified healthcare provider before starting therapy.

  • Adults (18 years and older)

    • The U.S. Food and Drug Administration (FDA) has not established a recommended dietary allowance (RDA) for silicon. The Food and Nutrition Board of the Institute of Medicine of the National Academies has not recommended a daily adequate intake (AI) for silicon. It has been suggested that an “apparent beneficial intake (ABI)” might be established for silicon and other ultratrace elements that have beneficial, if not essential, effects that can be extrapolated from animal research to humans.
    • Dietary intake of silicon in Western populations ranges from 20 to 50 milligrams daily. Further human research has shown that the mean daily intake of silicon is 30-33 milligrams in men and 24-25 milligrams in women. Higher levels of intake are associated with predominantly plant-based diets and lower levels with primarily meat-based diets.
    • Increasing the amount of silicon provided to adults with functioning kidneys who are receiving long-term parenteral nutrition to at least 10 milligrams daily may benefit bone health.
    • For brittle nail syndrome, 10 milligrams of silicon or 10 of milliliters colloidal silica have been taken by mouth daily.
    • For dementia (Alzheimer’s disease), 10 milligrams has been taken by mouth daily.
  • Children (under 18 years old)

    • There is no proven safe or effective dose for silicon in children.
    • The mean intake of silicon by infants receiving human milk is approximately 0.37 milligrams daily.



    The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

  • Allergies

    • Avoid with known allergy/hypersensitivity to any form of silicon or to silicon-based products.
  • Side Effects and Warnings

    • Silicon is likely safe at levels found naturally in food, water, and the air. Reports of adverse effects associated with silicon deficiency or excess in humans are lacking. Silicon is likely safe as found in cosmetic formulations and pharmaceutical preparations. Silicon may be fatal if large amounts are ingested, inhaled, or applied topically. Other potential side effects include fatigue, loss of appetite, and eye irritation.
    • Use cautiously in those prone to kidney stones. Long-term use of large amounts of antacids containing magnesium trisilicate may be associated with formation of silicon-containing stones. However, very few cases have been reported.
    • Use cautiously in patients undergoing chronic hemodialysis. Silicon may be found in high levels in dialysis fluids, and thus it may accumulate in the body. High silicon levels in these patients have been associated with problems in the kidneys, brain, nervous system, chest, bone, and liver.
    • Avoid occupational (in the air) exposure to crystalline silica. Exposure may cause lung diseases, such as silicosis (silica in the lungs), tuberculosis, chronic bronchitis, chronic obstructive pulmonary disease (COPD), and lung cancer. Those with occupational exposure may also develop lung hemorrhage (bleeding), inflammation of the kidneys, microscopic polyangiitis (inflammation of small vessels), rheumatoid arthritis, or scleroderma (a skin condition, particularly in males).
    • Avoid in pregnant or breastfeeding women, due to a lack of available scientific evidence.
    • Avoid use of 70-nanometer silica particles with acetaminophen, tetracycline, or 5-aminosalicylic acid, due to the increased risk of liver toxicity and death, although this has not been well studied in humans.
    • Avoid with known allergy or hypersensitivity to any form of silicon or to silicon-based products.
  • Pregnancy and Breastfeeding

    • Silicon is not recommended in pregnant or breastfeeding women, due to a lack of available scientific evidence. Silicon is found naturally in breast milk, formula, and cow’s milk.



    Most herbs and supplements have not been thoroughly tested for interactions with other herbs, supplements, drugs, or foods. The interactions listed below are based on reports in scientific publications, laboratory experiments, or traditional use. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy.

  • Interactions with Drugs

    • Silica particles in combination with 5-aminosalicyclic acid or acetaminophen may increase liver toxicity.
    • Taking silicon by mouth may affect aluminum absorption and excretion.
    • Silicon may interact with iron.
    • Silica particles in combination with tetracycline may be lethal, although this has not been well-studied in humans.
    • Silicon may have additive effects with drugs used for osteoporosis.
  • Interactions with Herbs and Dietary Supplements

    • Taking silicon by mouth may affect aluminum absorption and excretion.
    • Silicon may have additive effects with herbs or supplements used for osteoporosis.
    • Silicon may also interact with iron and germanium.


  • This information is based on a systematic review of scientific literature edited and peer-reviewed by contributors to the Natural Standard Research Collaboration ().



    Natural Standard developed the above evidence-based information based on a thorough systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to . Selected references are listed below.

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  • Brzezinski MB. Mining the diatom genome for the mechanism of biosilicification. Proc Natl Acad Sci U S A 2008;105(5):1391-2.
  • Carlisle EM. A silicon requirement for normal skull formation in chicks. J Nutr 1980;110(2):352-9.
    View Abstract
  • Carlisle EM. Biochemical and morphological changes associated with long bone abnormalities in silicon deficiency. J Nutr 1980;110(5):1046-56.
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  • Carlisle EM, Curran MJ. Effect of dietary silicon and aluminum on silicon and aluminum levels in rat brain. Alzheimer Dis Assoc Disord 1987;1(2):83-9.
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  • Domingo JL, Gómez M, Colomina MT. Oral silicon supplementation: an effective therapy for preventing oral aluminum absorption and retention in mammals. Nutr Rev 2011;69(1):41-51.
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  • Exley C. Darwin, natural selection and the biological essentiality of aluminium and silicon. Trends Biochem Sci 2009;34(12):589-93.
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  • Exley C. Silicon in life: whither biological silicification? Prog Mol Subcell Biol 2009;47:173-84.
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  • Haddad FS, Kouyoumdjian A. Silica stones in humans. Urol Int 1986;41(1):70-6.
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  • Jugdaohsingh R, Anderson SH, Tucker KL, et al. Dietary silicon intake and absorption. Am J Clin Nutr 2002;75:887-893.
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  • Jugdaohsingh R. Silicon and bone health. J Nutr Health Aging 2007;11(2):99-110.
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  • Nielsen FH. How should dietary guidance be given for mineral elements with beneficial actions or suspected of being essential? J Nutr 1996;126(9 Suppl):2377S-2385S.
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  • Nawijn SE, van der Linde H, Emmelot CH, et al. Stump management after trans-tibial amputation: a systematic review. Prosthet Orthot Int 2005;29(1):13-26.
    View Abstract
  • O’Brien L, Pandit A. Silicon gel sheeting for preventing and treating hypertrophic and keloid scars. Cochrane Database Syst Rev 2006;(1):CD003826.
    View Abstract
  • Sripanyakorn S, Jugdaohsingh R, Dissayabutr W, et al. The comparative absorption of silicon from different foods and food supplements. Br J Nutr 2009;102(6):825-34.
    View Abstract