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SILICON IN HUMANS: BENEFICIAL OR ESSENTIAL?
Henk-Maarten Laane, MD, GP, PhD, AAI
Keywords: silicon, humans, metabolism, clinical data, essentiality
Epstein (1999): An element is defined as quasi-essential if it is ubiquitous in plants, and if a
deficiency of it can be severe enough to result in demonstrable adverse effects or
abnormalities in respect to growth, development, reproduction, or viability.

Summary
url= http://www.agrisilica.co.za/testimonies.html
Relevant data on silicon research in humans have been inventoried. Although there are
reliable data on the clinical effects of Si in humans this mineral is almost completely neglected
in Medicine. These clinical effects are compared with the results of an open label study with a
liquid food supplement with bioavailable and stabilized oligomeric silicic acid and a low dose
of boric acid (OSAB) in Amsterdam during 2004-2007. OSAB showed to be a safe and
beneficial food supplement with significant effects on connective tissue, bone, cartilage, skin,
hair, nails, etc. The data confirm earlier clinical data in which show that Si is at least beneficial
for humans and animals. Due to a lack of sufficient data on the metabolism of Si in humans
essentiality has not (yet) been established. Silicon must be considered ‘quasi-essential’ as
defined by Epstein (1999) for plants.
Introduction

Silicon is contained in plants and also present in animals including humans. The quantity in
humans is 7 grams being more than all other trace elements together. Nevertheless Si is not
(or hardly) considered as beneficial: there is a lot of scepticism in regular Medicine because
silicon has been considered to be inert in humans. In 1973 the Joint FAO/WHO Expert
Committee on Food Additives says: ‘data on orally administered silica and silicates appear to
substantiate the biological inertness of these compounds’.
This negative attitude is surprising because for several hundreds of years extracts of Si-
accumulating plants like Equisetum arvense (horsetail) have been used therapeutically for
aging disorders, Alzheimer's disease, atherosclerosis, brittle hair, fractures, fragile nails, back
pain, osteoporosis, skin disorders, tendinitis, improved wound healing and wrinkles.
On the other hand there is a lack on sufficient data on the metabolism of silicon in animals
and humans. The absorption and bioavailability of silicon of the different silicon sources
(silicates, metasilicates, etc.) is hardly known. There are neither standardised methods nor
assays for assessing the silicon status in humans and animals.
In part 1 the clinical effects of Si in men are described followed by the data on metabolism of
Si in part 2. In part 3 the preliminary results of the Amsterdam Silicon Study in humans are
published, which will be compared with literature data.

1. Effects of silicon on tissues, organs and diseases
Bone and cartilage
In 1972, Carlisle showed that a Si deficient diet in chickens induces skeletal deformities and
joint abnormalities. Also in 1972, Schwartz published the same results in rats: deformities of
the skull and peripheral bones, characterized by poorly formed joints, defective endochondral
bone growth and reduced contents of articular cartilage, hexosamine, collagen and water.
The concentrations of minerals like calcium, magnesium, zinc and manganese were also to
low in the femur and vertebrae due to the diet only Si deficient.
Both studies mark the beginning of the recognition of the importance of silicon as an
beneficial even essential trace element that plays an important biological role in the
processes by which connective tissue, bone, cartilage and skin are formed.
A growing number of publications appear on the effects of Si on bone and cartilage as well in
men as in animals:
Schiano a.o. (1979) studied the activity of a soluble salt (drinkable and injectable) of Si on the
evolution of the trabecular bone volume (TBV) in men. They note a significant increase in the
TBV compared to controls.
Eisinger e.a. (1993) showed in a prospective study that Si induced a significant (P < 0.05)
increase in femoral bone mineral density in osteoporotic women compared to controls.
Rico et al. showed in 2000 the effects of Si supplement on preventing bone mass loss
induced by ovariectomy in rats. They proved that Si has an inhibitory effect on bone mass
loss as well as the stimulatory effect on bone formation, so Si may have a potential
therapeutic application in the treatment of involutive osteoporosis.
Calomme et al. showed the positive effects of orthosilicic acid on bone density in chicks
(2002) and on the bone density in ovariectomized rats (2004)..

Skin, hair and nails
The effects of Si on hair, skin and nails appear in regular literature:
Lassus performed an open study in 1993 with oral Si (colloidal silicic acid) during 3 months.
He found a (statistically significant) improvement in the thickness and turgor of the skin,
wrinkles and condition of the hair and nails.
Barel et al. investigated the Si supplementation on skin, nails and hair in a double-blind,
placebo controlled study. The (extra) Si had a significant positive effect on skin surface and
mechanical properties, and on brittleness of hair and nails.
The application of topical silicone gel is shown to be efficacious, both in the prevention and in
the treatment of hypertrophic scar.
Cardiovascular system / Atherosclerosis
Animal studies f.e. in rabbits (Loeper 1979) indicate that Si can reduce the formation of
atheromatous plaques. There is a low incidence of atherosclerosis in less developed
countries where foods are not heavily processed before consumption and the diet has a
higher Si content. In western diets the Si content is much lower and atherosclerosis is much
higher. Moreover Si intakes decrease significantly with age (Jugdaohsingh, et al., 2002)
suggesting that high Si intake is a factor in (partial) preventing atherosclerosis (Schwartz,
1977).
Other observations supporting the concept that sufficient silicon intake is important for healthy
blood vessels is that of an inverse relationship between the concentration of silicic acid in
drinking water and the prevalence of cardiovascular disease in Finland (Schwartz 1977).
Underlying mechanism: Silicon is ‘essential’ for the strength and integrity of the tunica intima,
the inner membrane of arteries.
Alzheimer's disease
Some evidence suggests that aluminum may increase the risk of developing Alzheimer's
disease. Si has been found to significantly reduce the absorption of aluminum by the body,
and researchers hypothesize that dietary Si may therefore reduce the risk of developing
aluminum induced Alzheimer's disease.
The protective role of silicon against aluminum was also confirmed in a French population
study of elderly subjects: high levels of aluminum in drinking water had a deleterious effect
upon cognitive function when the silicon concentration was low, but when the concentration of
silicon was high, exposure to aluminum appeared less likely to impair cognitive function.(14)
Other effects
There are several articles on silicon’s effect on the immune system:
Schiano et al (1979) showed that supplementation of soluble silicon in humans causes a clear
rise in the circulating lymphocytes and the immunoglobulins (especially IgG).
Seaborn et al. (2002) showed in rats that silicon has a functional role in lymphocyte
proliferation and that inadequate dietary silicon impairs splenic lymphocyte proliferation in
response to an immune challenge.
Mineo e.a. (2004) showed in in-vitro experiments that that silicon treatment is able to induce
proliferation of unstimulated macrophages and to maintain their viability

2. Silicon metabolism
General
Until now there are no validated methods for assessing the silicon status in humans and
animals. There are neither data nor validation of normal values of silicon in blood and different
tissues.
Moreover there are few reliable laboratory facilities available for analyzing blood and tissue
silicon levels.
Occurrence in food, food supplements and medicines
High levels of silicon are found in foods derived from plants, particularly grains such as oats,
barley or rice. After food processing much lower concentrations are found. Silicon levels in
foods from animal sources are relatively low.
Absorption and bioavailability
The bioavailability of silicon depends on the solubility of the compound or speciation
concerned. There is a lack of reliable data about the metabolism of silicon in humans. This is
partly due to the fact that there are many different forms of dietary silicon, all with different
absorptions. In one study, humans absorbed only about 1 % of a large single dose of an
aluminosilicate compound, while in other studies a single dose of stabilized monosilicic acid is
absorbed up to 80%.
Silicic acid is the bioavailable form, especially as mono (= ortho) and di silicic acid. It is easily
absorbed from the gastro-intestinal tract (50 – 80%). In the gastrointestinal tract Si, as
orthosilicic acid, is available from fluids (20-30%) and from silica in solid foods (70-80%),
which is hydrolyzed to orthosilicic acid.
The average absorption of daily Si intake is less than 50%.
The absorption is facilitated by aquaporins (a family of small (channel) proteins present in the
intracellular membranes, where they facilitate the transport of water and/or small neutral
solutes like urea, boric acid, silicic acid). In humans several aquaporins for OSA are identified.
Average daily intakes of Si vary between 13 and 62 mg/d. Mean Si intakes in men (33 mg/d)
are significantly higher than in women (25 mg/d).
Silicon intake decreases with age.
The dietary silicon intake is significantly correlated with urinary silicon excretion.
Another possibility for silicon uptake by the body is transdermal absorption. Lassus (1993)
showed the effects of oral and topical treatment of aged skin by a silicic gel. Because of the
combined method of administration the effects of dermal absorption alone remain unclear.
Still this dermal route can be an interesting option because foliar sprays with soluble silicon
used on plants show considerable biological effects.
Distribution
The human body contains approximately 7 grams of silicon, widely distributed in the tissues.
High levels are present in bone, nails, tendons and the walls of the aorta, with nails containing
the highest levels (up to 1500 mg/kg) and kidneys. Lower levels are present in red blood cells
or serum (approximately 44 mg/kg for red cells and 20 mg/kg for bound silicic acid in plasma,
in liver, spleen and lung. Silicon is found in breast milk.
Excretion
Silicon is predominantly and rapidly excreted in the urine, with smaller amounts being
eliminated in the feces.
Functions
Silicon is involved in the formation of bone and connective tissues:
1. Si facilitates the deposit of calcium and other minerals into bone tissue.
2. Silicon supplementation reduces the number of osteoclast cells, thus partially preventing
bone resorption and bone loss.
3. Si stimulates the osteoblasts
4. Si stimulates the synthesis of collagen.
5. Si facilitates the formation of glycosaminoglycan and collagen components of the bone
matrix through its role as a constituent of the enzyme of prolylhydrolase.
In the extracellular matrix (ECM) of the connective tissue in humans two main classes of
extracellular macromolecules are found: (1) polysaccharide chains of the class of
glycosaminoglycans (GAGs), which are usually found covalently linked to protein in the form
of proteoglycans, and (2) fibrous proteins, including collagen, elastin, a.o., which have both
structural and adhesive functions.
1. Glycosaminoglycans (GAGs) are unbranched, negatively charged molecules with a long
chain of repeating disaccharide units. Silicon is an integral component of four GAGs of
physiological importance: hyaluronic acid from umbilical cord, dermatan sulfate from mucosal
tissue, chondroitin-4-sulfate, and heparan sulfate. Si provides links within and between
polysaccharide chains of GAGs and also helps link GAGs to their respective protein. It is
found covalently linked to each GAG as a silanolate, an ether or ester-like derivative of silicic
acid, and forms R1—O—Si—O—R2 or R1—O—Si—O—Si—O—R2 continuous bridges. Thus,
Si helps form the structural framework of connective tissues by linking polysaccharide chains
together and contributes to the overall pliability of connective tissue.
2. Silicon-dependent enzymes link together simple chains of amino acids into collagen fibres.
Deficiency
Silicon deficiency has been produced experimentally in chicks and rats (Carlisle, 1972;
Schwartz, 1972).
Silicon deficiency has not been officially established as such in humans. Although silicon is
thought to be beneficial and maybe essential too many data are still lacking. For the definition
of essentiality and deficiency validated methods for assessing the silicon status in humans is
needed. The available data are also inadequate for recommendations on adequate nutritional
intakes on silicon.
Nevertheless brittle nails and thin hair, loss of elasticity of the skin, osteopenia and other
conditions should be regarded as deficiency symptoms, because they can be improved by
supplementation with (bioavailable) silicon.
Interactions
Silicon has been reported to interact with a number of minerals including copper, zinc and
germanium.
Silicon promotes the calcium absorption and metabolism to be absorbed.
Silicon and boron have synergistic effects.
Toxicity
Limited data are available on the oral toxicity of silicon in humans and no acute or chronic
toxicity data have been identified. The occurrence of silica stones has been reported in
patients on long term antacid therapy with magnesium trisilicate.
If inhaled at high concentrations over prolonged periods, certain forms of silica can cause
silicosis. Silica particles are inhaled into the alveoli of the lung, causing tissue damage that
ultimately results in fibrosis, which reduces the efficiency of the lungs and results in shortness
of breath.
Carcinogenicity and genotoxicity
Silicon was not carcinogenic in mice or rats at 5% in the diet. Silica was negative in the
Bacillus subtilis rec assay and was not mutagenic in the Ames test. Overall, inorganic silicon
compounds do not appear to have genotoxic potential.
Hazards
The interaction between silicon and aluminum has been researched in more detail as a
means of inhibiting aluminum toxicity. However the results are conflicting and it is possible
that silicon levels may be to low for significant effects in vivo.
Recommended amounts
Although silicon is thought to be beneficial and maybe essential to many data are still lacking.
This is the reason that recommendations on adequate nutritional intakes not have been
established.
There is an urgent need for assessing the silicon status in humans.
3. Amsterdam open label Silicon Study

Introduction
During the last 4 years (2004-2008) the possible side-effects of food supplement OSAB were
studied based on 13.500 users / year. Next the reported clinical effects after 3 and 9 months
in 98 consecutive patients (76 women and 22 men) were collected by standardized
questionnaires.
In an (offspring) observational study the efficacy of OSAB and glucosamine was compared in
patients with mild and moderate gonarthrosis (arthrosis of the knee joint).
OSAB is a liquid food supplement containing PEG-400 stabilized oligomeric (non colloidal)
silicic acid and a low dose of boric acid. By the (patented) stabilization procedure this solution
contains 0,9% silicic acid, while normally a saturated solution of silicic acid polymerizes
beyond 0,1%.
The choice for stabilized Si was based on a comparative study of Calomme et al. (2000) on
the bioavailability of several silicon sources. Stabilized silicic acid showed a superior
bioavailability compared to colloidal silicon, herbal silica and placebo. Moreover, OSAB is a
food supplement with stabilized silicic acid with a biological bioavailability of 70 – 80%.
Results
Safety / side effects.
During the 4 years period 15 side-effects were reported: nausea (5), pyrosis (3), diarrhoea
(3), rash (1), insomnia (2) and itching (1). No other event happened.
Some side effects like itching are related to the stabiliser PEG-400, as described in literature.
Based on literature data and this study non-colloidal silicic acid can be considered as (very)
safe.
Reported effects
A. Frequent reported effects (> 10%) were:
- (significant) improvement of the skin and wrinkles,
- improvement of brittleness of hair and nails / thicker hair / strong nails,
- improvement of arthralgia (joint pain) and back pain.
- boost in general wellbeing / boost of immunity / vitality
B. Less frequent reported effects (< 10%) were:
- improvement of skin disorders like psoriasis and eczema,
- improvement of arthritis (rheumatoid arthritis and psoriatic arthritis),
- improvement of wound healing (ulcus cruris),
- lowering of infection rate of URI’s (upper respiratory tact infections),
- improvement of allergy like hay fever and food allergy,
- antihypertensive effects,
- improvement of constipation,
- improvement of insomnia,
- improved sexual potency.
- improved fracture healing
C. Comparison of the effects of silicon and glucosamine on mild and moderate gonarthrosis.
The results of the reported effects showed in 9 of the 12 users (75%) a significant
improvement of the complaints in the silicon group (9 of 12), while the positive effects in the
glucosamine group were very limited to only 2 of the 13 (15,4%) after 4 months. A longer
follow-up was not possible because most of the glucosamine users stopped the glucosamine.
Discussion
The reported effects of this study match with literature data. OSAB proved to be a safe
nutrient with significant effects of hair, skin, nails and the locomotory system.
Moreover effects were reported against hypertension, insomnia and URI’s. The lowering
effect on hypertension can be due to a direct effect or to an improved absorption of
antihypertensive medication.
The effects on URI maybe related to the effects on allergies like hay fever. This can be
correlated with the described effects of the supplementation of soluble silicon on the immune
system showing a clear rise in the circulating lymphocytes and the immunoglobulins
(especially IgG) by Schiano et al (1979).
The reported affects against constipation and the side effect of diarrhoea must be regarded
as the effect of the stabilizer PEG-400 in the food supplement.
Improved sleep as reported by 7% seems to be related to the reported ‘boost’ in energy and
general well being. The effects continued at least for a one year’s period.
The (possible) effects of improved fracture healing are in line with silicon’s functions on bone
growth and mineralization.
The potential use of silicon as a therapeutic in arthritis and arthrosis needs more research.
Based on the preliminary results in mild and moderate gonarthrosis silicon could haves a
potential as a medicine because its significant better effects than glucosamine after 4 months.
More extensive double-blind clinical trials are needed.
4. Conclusion
There is a parallel in the recognition of the importance of silicon in Agriculture and Medicine.
Although silicon gets more attention and appreciation in Agriculture it has been, up til now, a
relatively unknown trace element in Medicine. The essentiality of silicon for man has not been
established and the functional role for silicon in humans lacks sufficient data, also due to the
absence of validated blood and tissue levels. A world wide lack of reliable facilities for silicon
analyses is another important factor. Much more information on metabolism is needed. There
are hardly reliable laboratory facilities available.
Silicon intake seems to be a major dietary determinant of bone mineral density in humans.
Optimal bone health depends on many factors amongst silicon, which facilitates bone growth
and bone calcification and mineralization. The dietary shift to low silicon intake in western diet
and a decreased intake with aging must be considered as a major risk factor for osteoporosis
and bone fractures. Increasing the body silicon content by foods, plant extracts or
supplements has the promise of anti aging effects and prevention on osteoporosis and
possibly Alzheimer’s. Silicon’s potential for other diseases needs much more research in
Medicine.
Based on all research so far silicon should be considered in humans as ‘quasi-essential’ as
defined by Epstein(1999).
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