Background

• 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.

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