Silicon is one of the most prevalent elements on earth; it makes up more than a quarter of the earth’s crust, mostly as silicon dioxide. Silicon is hypothesized to play an essential role in the body, but this is uncertain. Silicon supplements are currently marketed for improving the health of bone, skin, hair, and nails. The substance silicone, once used in breast implants, also contains silicon, but in an unusual synthetic form.
Scientists have found it difficult to determine whether silicon is an essential nutrient in humans, and if it is, to identify the necessary daily intake.1 Silicon is found whole grains, some root vegetables, and beer. Silicon-containing chemicals are also added to prevent caking in products such as salt and baking soda. The average intake of silicon is approximately 10–40 mg daily.
When used as a supplement, common recommended dosage levels range from 10 to 30 mg per day.
Silicon is a constituent of the enzyme prolylhydrolase, which helps the body produce collagen and glycosaminoglycans. In addition, silicon is directly found in protein complexes that include glycosaminoglycans. These substances are essential for healthy bone, nails, hair, and skin.
Animal studies hint that silicon deprivation causes bone weakness as well as slowed wound healing.2-6 Artificial bone grafts containing silicon have been used successfully in surgical repair of damaged bones.7-11 Furthermore, in a major observational study, higher intake of silicon was associated with stronger bones.12 Based on these findings, silicon has been proposed as a bone-strengthening substance for preventing or treating osteoporosis. However, only double-blind, placebo-controlled studies can prove a treatment effective. (For information on why such studies are essential, see Why Does This Database Rely on Double-blind Studies?) Only one such study has been performed on silicon as a treatment for osteoporosis, and it found equivocal results at best.19
One double-blind, placebo-controlled study did find potential benefits with a proprietary silicon supplement for aging skin, brittle nails, and brittle hair.5 Fifty women with sun-damaged skin were give either 10 mg silicon daily (as “choline stabilized orthosilicic acid”) or placebo for 20 weeks. Measurements of skin roughness and elasticity showed improvement in the silicon group as compared to the placebo group. Brittleness of hair and nails also improved. However, this study, performed by the manufacturer of the product, did not meet the highest standards of design and reporting. Another study of the same product demonstrated stronger and thicker hair over a nine month period in women with fine hair compared to placebo.20
Silicon has also been claimed to help prevent atherosclerosis, but there is no meaningful evidence to support this claim.
Another potential use of silicon relates to the aluminum hypothesis of Alzheimer’s disease, the theory that aluminum toxicity is prominent contributor to the development of this condition. On some websites promoting silicon supplements, it is said that increased dietary silicon decreases aluminum absorption. However, whether or not silicon actually has this effect remains unclear.13-17 Furthermore, the hypothesis that aluminum is a major risk factor for Alzheimer’s disease has lost ground in recent years.
Silicon is thought to be a safe supplement when used at doses similar to the average daily intake. Based on conservative evaluation of data from animal studies, it has been estimated that even a much higher dose of 13 mg per kilogram of body weight should present little to no risk. (For an adult of average weight, this works out to 760 mg daily.)18 However, maximum safe doses in young children, pregnant or nursing women, or people with severe liver or kidney disease have not been established.
1. Institute of Medicine Panel on Micronutrients, Subcommittees on Upper Reference Levels of Nutrients and of Interpretation and Use of Dietary Reference Intakes, and the Standing Committee on the Scientific Evaluation of Dietary Reference Intakes. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, D.C.: National Academies Press; 2000.
2. Seaborn CD, Nielsen FH. Silicon deprivation decreases collagen formation in wounds and bone, and ornithine transaminase enzyme activity in liver. Biol Trace Elem Res. 2002;89:251–61.
3. Rico H, Gallego-Lago JL, Hernandez ER, et al. Effect of silicon supplement on osteopenia induced by ovariectomy in rats. Calcif Tissue Int. 2000;66:53–5.
4. Carlisle EM. Silicon as a trace nutrient. Sci Total Environ. 1989;73:95–106.
5. Barel A, Calomme M, Timchenko A, et al. Effect of oral intake of choline-stabilized orthosilicic acid on skin, nails and hair in women with photodamaged skin. Arch Dermatol Res. 2005 Oct 5 [Epub ahead of print].
6. Jugdaohsingh R, Anderson SH, Tucker KL, et al. Dietary silicon intake and absorption. Am J Clin Nutr. 2002;75:887–93.
7. Yin X, Stott MJ. Theoretical insights into bone grafting silicon-stabilized alpha-tricalcium phosphate. J Chem Phys. 2005;122:024709.
8. Ito M, Abumi K, Moridaira H, et al. Iliac crest reconstruction with a bioactive ceramic spacer. Eur Spine J. 2005;14:99–102.
9. Wheeler DL, Eschbach EJ, Hoellrich RG, et al. Assessment of resorbable bioactive material for grafting of critical-size cancellous defects. J Orthop Res. 2000;18:140–8.
10. Radin S, Reilly G, Bhargave G, et al. Osteogenic effects of bioactive glass on bone marrow stromal cells. JBiomed Mater Res A. 2005;73A:21–9.
11. Phan PV, Grzanna M, Chu J, et al. The effect of silica-containing calcium-phosphate particles on human osteoblasts in vitro. J Biomed Mater Res A. 2003;67:1001–8.
12. Jugdaohsingh R, Tucker KL, Qiao N, et al. Dietary silicon intake is positively associated with bone mineral density in men and premenopausal women of the Framingham Offspring cohort. J Bone Miner Res. 2004;19:297–307.
13. Drueke TB, Jouhanneau P, Banide H, et al. Effects of silicon, citrate and the fasting state on the intestinal absorption of aluminium in rats. Clin Sci (Lond). 1997;92:63–7.
14. Jugdaohsingh R, Reffitt DM, Oldham C, et al. Oligomeric but not monomeric silica prevents aluminum absorption in humans. Am J Clin Nutr. 2000;71:944–9.
15. Reffitt DM, Jugdaohsingh R, Thompson RP, et al. Silicic acid: its gastrointestinal uptake and urinary excretion in man and effects on aluminium excretion. J Inorg Biochem. 2000;76:141–7.
16. Belles M, Albina ML, Sanchez DJ, et al. Lack of protective effects of dietary silicon on aluminium-induced maternal and developmental toxicity in mice. Pharmacol Toxicol. 1999;85:1–6.
17. Belles M, Sanchez DJ, Gomez M, et al. Silicon reduces aluminum accumulation in rats: relevance to the aluminum hypothesis of Alzheimer disease. Alzheimer Dis Assoc Disord. 1998;12:83–7.
18. U.K. Food Standards Agency. Risk assessment – silicon. Available at: http://www.food.gov.uk/multimedia/pdfs/evm_silicon.pdf. Accessed July 7, 2005.
19. Spector T, Calomme M, Anderson S, et al. Effect on bone turnover and BMD of low dose oral silicon as an adjunct to calcium/vitamin D3 in a randomized, placebo-controlled trial. Poster presentation, ASBMR 27th Annual Meeting, Nashville, Tennessee, September 2005.
20. Wickett RR, Kossmann E, Barel A, et al. Effect of oral intake of choline-stabilized orthosilicic acid on hair tensile strength and morphology in women with fine hair. Arch Dermatol Res. 2007 Oct 25. [Epub ahead of print]
Last reviewed December 2015 by EBSCO CAM Review Board Last Updated: 12/15/2015