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Minerals in Detail
Chemical Details | Description | Industrial Applications |
In Nature | Health Impacts | Daily Intake
SILICON
Silicon - chemical details
| Symbol | Si |
| Atomic number | 14 |
| Atomic mass | 28.0855 g.mol-1 |
| Electronegativity | 1.8 (according to Pauling) |
| Density | 2.33 g.cm-3 at 20 °C |
| Melting point | 1410 °C |
| Boiling point | 3265 °C |
| Vanderwaals radius | 0.132 nm |
| Ionic radius | 0.271 (-4) nm |
| 0.041(+4) |
| Isotopes | 5 |
| Electronic configuration | [Ne] 3s23p2 |
| Energy of first ionisation | 786.3 kJ.mol-1 |
| Energy of second ionisation | 1576.5 kJ.mol-1 |
| Energy of third ionisation | 4354.4 kJ.mol-1 |
| Standard potential | -0.91 V |
| Discovered | 1823 - Jons Berzelius |
Chemical Details | Description | Industrial Applications |
In Nature | Health Impacts | Daily Intake
Silicon - Description
Silicon is the most abundant electro-positive element in the Earth’s crust. It’s a metalloid with a marked metallic luster and is very brittle. It is
usually tetravalent in its compounds, although sometimes its bivalent, and it’s purely electro-positive in its chemical behaviour. Moreover, penta-
coordinated and hexa-coordinated silicon compounds are also known. Natural silicon contains 92.2% of the isotope 28, 4.7% of silicon 29 and 3.1% of silicon
30. Apart from those stable natural isotopes, various radioactive artificial isotopes are known.
Elemental silicon has the physical properties of metalloids, similar to the ones or germanium, situated under it in group
IV of the periodic table. Silicon is an intrinsic semiconductor in it’s purest form, although the intensity of its semiconduction is highly increased by
introducing small quantities of impurities. Silicon is similar to metals in its chemical behaviour.
Chemical Details | Description | Industrial Applications |
In Nature | Health Impacts | Daily Intake
Silicon - Industrial applications
Silicon is important in the manufacture of cement, ceramics, semi-conductors, plastics and photovoltaic cells among many others. For details on
industrial applications and impact on the environment see www.lenntech.com/Periodic-chart-elements/Si-en.htm
Chemical Details | Description | Industrial Applications |
In Nature | Health Impacts | Daily Intake
Silicon - In natural form
Silicon is more abundant than any other element except oxygen. It constitutes 27.72% of the Earth's solid crust, while oxygen constitutes 46.6%, and the
next most abundant, aluminium, makes up 8.13%.
Sand is used as source of the silicon produced commercially. A few silicate minerals are mined, like talc and
mica. Other mined silicates include feldspars, olivine, vermiculite, perlite, and kaolinite. At the other extreme there are forms of silica so rare that
they are desirable for this reason alone. These include gemstone opal, agate and rhinestone.
Chemical Details | Description | Industrial Applications |
In Nature | Health Impacts | Daily Intake
Silicon - Impact on health
The human body contains approximately 7 grams of silicon, which is present in various tissues and body fluids. The silicon in tissues is usually bonded to
glycoproteins such as cartilage, whereas the silicon in blood is almost entirely found as either free orthosilicic acid or linked to small compounds.
The biological requirement for silicon was first demonstrated by Edith Carlisle and Klaus Schwarz in experiments with rats and chickens that were fed
silicon-deficient diets. These experiments demonstrated that nutritional silicon deficiency causes skeletal deformities such as abnormal skull and long bone
structure, as well as poorly-formed joints with decreased cartilage content. Detailed biochemical analysis revealed that silicon is an essential nutrient
for the structural integrity and development of connective tissue.
Silicon's most popular use is as a nutritional supplement to strengthen not only the bones and connective tissues, but also hair, nails and skin. However,
we have been unable to locate reputable research that supports the value of silicon supplements in humans for these latter purposes, though plenty of
anecdotal evidence.
Silicon has an important role in preventing osteoporosis. Bone loss occurs generally with aging, but accelerates during menopause and its resultant estrogen
deficiency. Studies with animals indicate that silicon supplementation reduces the number of osteoclast cells, partially preventing bone resorption and bone
loss1. On the other hand, Keeting et al, demonstrated that silicon stimulates DNA synthesis in osteoblast-like cells2.
Animal models for osteoporosis using estrogen deficient rats show silicon supplementation preventing bone loss3. In a 1993
Study of 53 osteoporotic women, silicon supplementation was associated with a significant increase in mineral bone density of the femur4.
In addition to connective tissue and bone health, several other health benefits such as protection of arterial tissue and defense against aluminium toxicity
may derive from silicon. It is believed that silicon bonds with aluminium in food, and in so doing reduces gastrointestinal absorption of aluminium. In rat
studies, silicon was found to prevent the accumulation of aluminium in the brain5. The protective role of silicon on
aluminium was confirmed in a French study of elderly subjects. High levels of aluminium in drinking water had a deleterious effect upon cognitive function
when the silicon concentration level was low. When the silicon concentration was high, exposure to aluminium appeared less likely to impair cognitive
function6.
Experiments with rabbits eating a high cholesterol diet demonstrate silicon’s benefit as a defense against atherosclerosis7.
Chemical Details | Description | Industrial Applications |
In Nature | Health Impacts | Daily Intake
Silicon - Recommended daily (RDA) & maximum (Limit) intake
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Risk free |
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intake? |
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Food sources? |
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Result of overdose? |
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RDA |
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Limit |
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Infants
0-6 mo
7-12 mo
Children
1-3 y
4-8 y
Males
9-13 y
14-18 y
19-30 y
31-50 y
50-70 y
> 70 y
Females
9-13 y
14-18 y
19-30 y
31-50 y
50-70 y
> 70 y
Pregnancy
< 19 y
19-30 y
31+ y
Lactation
< 19 y
19-30 y
31+ y |
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ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
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ND |
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ND
ND
ND
ND
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ND
ND
ND
ND
ND
ND
ND
ND
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ND
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Plant-based foods |
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There is no evidence that silicon that occurs naturally in food and water produces adverse health effects |
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Explanations:
ND = Not determinable. There is either insufficient data on adverse effects and/or concern with the body's ability to handle excess amounts. In most
instances it is wise not to supplement for this particular element, but to rely on diet to provide sufficient quantities.
RDA = Recommended Dietary Allowance. May be used as a goal for daily intake. RDAs are set at a level that should meet the needs of 97-98% of all individuals.8, 9, 10, 11
Limit = The maximum level of daily nutrient intake from all sources that is highly likely to pose no risk of adverse effects.8, 9, 10, 11
References:
- Hott M., de Pollak C., Modrowski D. & Marie P. (1993). Short term effects of organic silicon on trabecular bone in mature ovariectomized rats. Calcified Tissue Int 1993 53:174-179
- Keeting P., Oursler M., Wiegand K. & Spelsberg T. (1992). Zeolite A increases proliferation, differentiation, and transforming growth factor beta production in normal adult human osteoblast-like cells in vitro. J Bone and Miner Res 1992, 7 (11):1281-1289
- Rico H., Gallego-Lago J., Hernandez E., Villa A., Sanchez-Atrio A., Seco C., & Gervas J. (1999). Effect of silicon supplement on osteopenia induced by ovarianectomy in rats. Calcified Tissue Int 1999, 66:53-55
- Eislinger J., & Clariet D. (1993). Effects of silicon, fluoride, etidronate and magnesium on bone mineral density: a retrospective study. Magnesium Research 1993, 6(3):247-249
- Carlisle E., & Curran M. (1987). Effect of dietary silicon and aluminum on silicon and aluminum levels in rat brain. Alzheimer Dis Assoc Disord 1987, 1:83-89
- Jacqmin-Gadda H., Commenges D., Letenneur L., & Dartigues J. (1996). Silica and aluminium in drinking water and cognitive impairment of elderly. Epidemiology 1996, 7:281-285.
- Loeper J., Goy-Loeper J., Rozensztajn L., & Fragny M. (1979). The antiatheromatous action of silicon. Atherosclerosis 1979, 22:397-408.
- Standing Committee on the Scientific Evaluation of Dietary Reference Intakes (1997). Dietary Reference Intakes for Calcium, Phosphorous, Magnesium, Vitamin D, and Fluoride.Food and Nutrition Board: Institute of Medicine.
- Standing Committee on the Scientific Evaluation of Dietary Reference Intakes (1998). Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6,
Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline.Food and Nutrition Board: Institute of Medicine.
- Standing Committee on the Scientific Evaluation of Dietary Reference Intakes (2000). Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids.Food and Nutrition Board: Institute of Medicine.
- Standing Committee on the Scientific Evaluation of Dietary Reference Intakes (2001). Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc.Food and Nutrition Board: Institute of Medicine.
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