Silicon: An Overlooked Trace Mineral
 
 Silicon, an abundant trace mineral in nature is proving to be an essential ingredient for stronger bones, better skin and more flexible joints. Including silicon in your diet may boost the benefits of calcium, glucosamine and vitamin D. Here are some of the latest findings on this overlooked mineral.

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(1,2) 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.(3,4)

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.

Silicon in tissue and joints

Connective tissue is composed of cells which produce the fibrous protein matrixes of collagen and elastin, as well as the hydrated (water retaining) network of amino-sugars called glycosaminoglycans (GAG) or muco- polysaccharides (MPS). Silicon is believed to stabilize the glycosaminoglycan network.(5)

The amino-sugar glucosamine, which is also needed for the biosynthesis of GAGs, has been clinically proven to be effective in the treatment of arthritis.(6) Given silicon's chemical association with GAGs, it seems that the combination of both glucosamine and silicon could have a complementary therapeutic value in the treatment of arthritis and other related connective tissue diseases.

Silicon, bone and osteoporosis

Bone is actually a special type of connective tissue. Silicon is a major ion in osteogenic cells, which are the bone-forming cells in young, uncalcified bone. As the bone matures, the silicon concentration declines and deposits of calcium and phosphorous are formed simultaneously. In other words, the more "mature" the bone tissue, the lower the silicon concentration in the bone. Therefore, it has been concluded that silicon acts as a regulating factor for the deposition of calcium and phosphorous in bone tissue.(7)

Silicon's regulatory action in bone calcification and its vital role as a structural component of connective tissue are the reasons for silicon's classification as an essential trace element in animal and human nutrition.

Silicon plays an ongoing role in maintaining bones after their formation. Bone is a dynamic, living tissue system that balances bone formation by osteoblast cells and the ongoing reabsorption of bone tissue by osteoclast cells. (Bone minerals are dissolved and organic bone matrix components such as collagen are digested by the action of osteoclast cell.)

Osteoporosis occurs when there is a low rate of bone formation and a high rate of bone reabsorption, thus leading to a decline in bone mineral density and a decreased mechanical strength of the bone. Bone loss occurs generally with aging, but a clear acceleration occurs during menopause or following a failure or removal of the ovaria, which leads to estrogen deficiency.

Studies with animals indicate that silicon supplementation reduces the number of osteoclast cells, thus partially preventing bone reabsorption and bone loss.(8) On the other hand it was shown in vitro that silicon compounds stimulate the DNA synthesis in osteoblast-like cells.(9)

Animal models for osteoporosis using estrogen deficient rats demonstrate that silicon supplementation can prevent bone loss.(10) In a clinical study of 53 osteoporotic women, silicon supplementation was associated with a significant increase in the mineral bone density of the femur.(11) The positive results of these studies suggest that silicon supplementation, along with calcium and vitamin D, may be useful in the fight against osteoporosis.

Silicon's other uses

In addition to connective tissue and bone health, several other promising health benefits of silicon, such as protection against aluminum toxicity and protection of arterial tissue have been reported.

As much as aluminum has been found in brain lesions of Alzheimer's patients, several researchers have suggested that aluminum toxicity may be involved in the pathology of Alzheimer's disease and other neurological disorders. In studies with rats,(13) silicon was found to prevent the accumulation of aluminum in the brain. It is believed that silicon bonds with aluminum in food and beverages, thereby reducing the gastrointestinal absorption of aluminum.

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)

Atherosclerosis is a condition characterized by the formation of plaque in the arteries. Plaque is formed when damaged artery tissue is not properly repaired, thus allowing scar tissue, oxidized cholesterol and other materials to obstruct the normal blood flow.

Experiments with rabbits fed a high-cholesterol diet demonstrated that supplementation with silicon protected the rabbits from developing artherosclerosis. Aside from protection against artherosclerosis, silicon is a vital structural component of arteries. However, the silicon concentration of arteries declines with age, most likely increasing the risk of lesions and plaque formations.(15,16)

Silicon in your diet

The daily dietary intake of silicon is estimated to be between 20 to 50 mg,17 with lower intakes associated with animal-based diets and higher intakes associated with vegetarian diets. Plants absorb orthosilicic acid from the soil and convert it into polymerized silicon for mechanical and structural support.18 This explains why fiber-rich foods such as cereals, oats, wheat bran and vegetables have a high silicon concentration. An unbalanced diet with a limited supply of vegetables, fruits and cereals will be low in silicon concentration.

While whole grain foods are a good, natural source of silicon, the silicon from these foods is insoluble and cannot be directly absorbed in the gastro-intestinal tract. Silicon in food is solubilized by stomach acid into orthosilicic acid, which absorbs directly through the stomach wall and the intestine into the blood. Lower stomach acidity, whether due to illness or age, diminishes our ability to metabolize silicon from food sources.

Aging is reported to be associated with an increasing gastric pH. In this view elderly people will have a decreased capacity to convert dietary silicates into bioavailable orthosilicic acid. The refining and processing of food, which removes silicon-containing fibers, contributes to a lower dietary silicon intake. Additionally, many of the additives used in the food industry interfere with the uptake of silicon.

In fact, these additives can (a) increase the gastric pH and thereby decrease the rate of hydrolysis of dietary silicates, (b) promote polymerization of orthosilicic acid and (c) chelate minerals in general which are then eliminated through the intestinal tract without absorption. The extensive re-use of soils and the application of aquacultures minimalize the essential supply of orthosilicic acid to plants.

The resulting crops have a less rigid structure due to decreased biosynthesis of phytolytic fibers and specific epidermal cells which contain silica structures. Consequently these crops will have a lower silicon concentration and contribute less to the dietary silicon intake compared to crops which have been cultivated on a natural, mineral rich soil. Given all these factors, it is not surprising that silicon supplementation may be useful for a complete and balanced diet.

When selecting a silicon supplement, the most important considerations should be safety and bioavailability. (Bioavailability is a complex term for the degree of absorption and the biological response to the silicon compounds which are present in the product.) Organic silicon compounds, which are laboratory synthesized, contain silicon-carbon bonds. These molecules are normally not present in biological systems and can be very toxic. For this reason it is safest to use silicon compounds that are already present in nature or compounds that are the derivatives of natural products.

Common silicon supplements include:

Plant extracts:
Bamboo and algae usually have high silica concentrations. However, plant extracts are often not standardized and the silicon concentration in these products varies greatly. As the silicon from plant extracts cannot be absorbed directly through the stomach wall, the bioavailability of these products requires high stomach acidity in order to produce soluble orthosilicic acid.

Colloidal silicon gel:
These products offer large, insoluble, polymer molecules of silicic acid suspended in water. Like plant extracts, these polymer-molecules cannot be absorbed directly through the stomach wall and therefore have a low rate of absorption. The stomach's ability to produce soluble orthosilicic acid is also limited to low concentration levels due to orthosilicic acid's limited stability.

Stabilized orthosilicic acid:

Now on the market is a liquid, stabilized orthosilicic acid concentrate. A research group from the University of Antwerp in Belgium has published a supplementation study describing a high rate of silicon absorption from a liquid silicon supplement containing 2% silicon in the form of stabilized orthosilicic acid.

In the six-month study with calves, the total dietary silicon intake was increased by only 5% in the form of stabilized orthosilicic acid. Even with such a small dose of orthosilicic acid, the supplemented group showed 70% higher blood silicon levels than the unsupplemented group. These higher silicon blood levels also translated into a 12% higher collagen concentration in the skin of supplemented animals compared to unsupplemented animals. This study clearly demonstrated that the bioavailability of stabilized orthosilicic acid concentrate is very high compared to dietary silicon.(19)

Two independent Belgian research groups demonstrated both in a comparative human study that the total silicon absorption by the human body is considerably higher (more than 2.5 times higher) after supplementation of stabilized orthosilicic acid ,compared to plant extracts or colloidal supplements. In fact this supplementation resulted in a statistical significant increase in silicon absorption compared to the placebo.

Without exception, each test subject had a similar absorption from orthosilicic acid, whereas large differences among subjects were found for the other silicon supplements.(20,21)

The bone stimulatory properties of silicon were recently investigated in an extended study on chicks. For the first time a normal diet was used instead of silicon deficient diet, which made it possible to observe the superior biological action of silicon in supplemented chicks compared to a control group. The silicon was added to the drinking water of the chicks, which increased the total dietary silicon intake less than 0.5%. Despite this extremely low dose a significant effect was found on both the calcium concentration in the blood and the density of thigh bones (femura).

In fact, the chicks had, after six weeks supplementation, 5.6% higher bone density in the hip region and 4.25% higher bone density at the midshaft of their thigh bones compared to non-supplemental chicks. These results show clearly that stabilized silicon (choline-silicon complex) was able to stimulate the bone formation machinery resulting in a higher density.(22)

Based on all the current research, silicon is now being considered a critical nutrient to better manage the effects of age on the body. Increasing the silicon in your body can occur through foods, plant extracts or supplements. Those with osteoporosis should especially consider the benefits of consistent silicon intake.

References:

1. Calisle EM. Silicon, an essential element for the chick. Science 1972, 178:619-62

2. Schwartz K, et al. Growth-promoting effects of silicon in rats. Nature 1972, 239:333-334.

3. Seaborn C, et al. Effects of germanium and silicon on bone mineralization. Biological Trace Element Res 1994, 42:151-164.

4. Seaborn C, et al. Silicon deprivation decreases collagen formation in wounds and bone, and ornithine transminase enzyme activity in liver. Biol Trace Elem Res 2002, 89(3):251-61.

5. Schwartz K. A bound form of silicon in glycosaminoglycans and polyuronides. Proc Nat Acad Sci USA 1973, 70(5):1608-1612.

6. Reginster J, et al. Long-term effects of glucosamine sulphate on osteoarthritis progression: a randomized, placebo-controlled clinical trial. Lancet 2001, 357:251-56.

7. Carlisle EM. Silicon: a possible factor in bone calcification. Science 1970, 167:179-280.

8. Hott M, et al. Short-term effects of organic silicon on trabecular bone in mature ovariectomized rats. Calcif Tissue Int 1993, 53:174-179.

9. Keeting et al. 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.

10. Rico H, et al. Effect of silicon supplement on osteopenia induced by ovariectomy in rats. Calcif Tissue Int 1999, 66:53-55.

11. Eisinger J, Clariet D. Effects of silicon, fluoride, etidronate and magnesium on bone mineral density: a retrospective study. Magnesium Research 1993, 6(3):247-249.

12. Candy JM et al. Aluminosilicates and senile plague formation in Alzheimer's disease. Lancet 1986, 1:354-356.

13. Carlisle EM, Curran MJ. Effect of dietary silicon and aluminum on silicon and aluminum levels in rat brain. Alzheimer Dis Assoc Disord 1987, 1:83-89.

14. Jacmin-Gadda H, et al. Silica and aluminium in drinking water and cognitive impairment in the elderly. Epidermiology 1996, 7:281-285.

15. Loeper J, et al. Study of fatty acids in atheroma induced in rabbits by an atherogenic diet with or without silicon IV treatment. Life Sciences 1988, 42:2105-2112.

16. Loeper J, et al. The antiatheromatous action of silicon. Atherosclerosis 1979, 33:397-408.

17. Pennington JAT. Silicon in foods and diets. Food Addit Contam1991, 8:97-118.

18. Sangstet AG, et al. Silica in higher plants nutrition. In Silicon Biochemistry, CIBA Foundation Symposium 121, John Wiley and Sons, New York, p. 90-111.

19. Calomme M, Vanden Berghe D. Supplementation of calves with stabilized orthosilicic acid. Biol Trace Elem 1997, 56:153-156.

20. Calomme M, et al. Silicon absorption from stabilized orthosilicic acid and other supplements in healthy subjects. Trace elements in Man and Animals 10, ed by Roussel et al. Plenum, p. 1111-1114.

21. Van Dyck K, et al. Bioavailability of silicon from food and food supplements. Fresenius J Anal Chem 1999, 363:541-544.

22. Calomme M, et al. Effect of choline stabilized orthosilicic acid on bone density in chicks. Calcif Tissue Int 2002, 70:292.
 

Silicon and Equine Bone Health

 

Brian D. Nielsen, Ph.D., PAS, Dpl. ACAN

Kari E. Krick, M.S.

Michigan State University, Department of Animal Science

East Lansing, MI  48824-1225

 

Prevention and treatment of skeletal injuries in performance horses is an on-going struggle for horse owners and trainers.  Lameness tends to be one of the primary reasons why a horse’s athletic performance either declines or never reaches its potential.  Reducing the injury rate of horses is not only a major animal welfare issue; but also it represents a substantial economic concern.  With these points in mind, it is understandable for horse owners and trainers to be continually searching for ways to keep their horses sound.

 

The implementation of proper training techniques is an important way to reduce injuries, which, of course, is much more complicated than one may think.  Contrary to popular belief, for example, there are many advantages to training young horses that are still skeletally immature.  While the young horse is growing, the skeletal tissue has the greatest capacity to strengthen.  Though not commonly recognized as such, bone is a very dynamic tissue that constantly changes to accommodate forces placed upon it.  When one increases the load upon bone, it becomes stronger particularly if it is given sufficient time to respond to the forces without being overloaded.  In contrast, when load is reduced on bone, it responds by becoming weaker.  These facts point out the inherent problems with stalling of young horses without giving them sufficient exercise.

 

The question arises as to the proper intensity and amount of training to give horses so that their bones are strengthened without being damaged.  Through scientific studies, we are gradually finding answers to determine how much exercise is needed to optimize skeletal strength, but our understanding of these aspects of equine physiology will require ongoing research.

 

Since there are many questions remaining as to what are effective injury reducing training programs, owners and trainers have been adopting other ways to deal with the problems of equine lameness.  The fields of equine physiology and nutrition are providing solutions through creation of scientifically formulated diets for the purposes of not only providing required sustenance but also for their prophylactic benefits generally through manipulated bone health.  Bioavailable silicon, for example, is a scientifically discovered essential nutrient that studies indicate has promising benefits when added to the equine diet.

 

Silicon in the Environment

 

Silicon is the second most common element of the Earth’s crust that is found throughout the environment; it is, for instance, a major constituent of sand.  Silicon dioxide (SiO₂) in the quartz crystals of sand cannot be absorbed by the horse (it is not bioavailable), which renders it useless as a nutritional aid.  Plants, however, use silicon to provide rigidity and structure to some of their cell walls, from which horses are able to obtain small amounts in their normal diet of forage and grain.  It should be noted, however, that processing of commercial horse feeds appears to reduce silicon’s availability from these sources.

 

Despite its ubiquitous nature, surprisingly little is known about the nutritional importance of silicon in the diet of mammalian species.  That being said, the American Institute of Nutrition recently reformulated their published formulas of purified diets for experimental rodents, and made the decision to include silicon as a required nutrient.  This change was brought about as a result of research demonstrating that it can interact with other nutrients for apparent beneficial effects.

 

 

Silicon in Bone and Connective Tissues

 

Most people think of bone as being made primarily from the minerals calcium and phosphorus.  Much more, of course, goes into bone than just these two minerals.  To begin with, bone is constantly undergoing changes as it removes old or damaged components and replaces them with new healthy elements.  Silicon plays a role in the development of new bone, and it is involved with the calcification process.  Interestingly, in the early stages of calcification, silicon and calcium content are low but both increase as mineralization progresses.  As bone becomes fully mature, however, silicon content decreases while calcium remains high.  Though its exact role has yet to be determined, silicon would appear to be exceptionally critical in the young, growing animal when the skeleton is undergoing rapid development.  Support for the theory that silicon is involved in an early stage of bone formation is founded upon studies in which chicks had defective bone growth after being fed a silicon-deficient diet.

 

While being involved in the mineralization process of bone, silicon also appears to play a major role in the formation of the collagen matrix of bone and cartilage.  This matrix is necessary to prevent these tissues from becoming brittle and susceptible to damage.  When silicon is deficient in the diet, the formation of the matrix appears to be limited; potentially resulting in even greater problems than if it is deficient in the mineralization process.  In tissue cultures of bone and cartilage, bone growth induced by silicon appears to be mainly due to an increase in collagen content.  The formation of glycosaminoglycans, the major polymeric molecule of the bone matrix, has also been shown to require silicon.  Again, when chicks were fed a silicon-deficient diet, collagen content in the frontal bones was reduced.  Additionally, the amount of articular cartilage was reduced compared to chicks that were supplemented with silicon.  At the molecular level, silicon has been shown to be involved with mucopolysaccharide synthesis in the formation of articular cartilage and connective tissue, and to be an integral component of the mucopolysaccaride-protein complex and collagen of connective tissues.

 

Supplemental Silicon in Horses

 

Though the National Research Council (1989) has not specified a specific requirement for silicon in horses, benefits have been demonstrated by feeding a bioavailable silicon source.  As part of a large, blinded FDA-controlled study, dramatic decreases in injury rates were reported in race-trained Quarter Horses fed a supplemental silicon source.  The control group of horses not receiving supplemental silicon had more horses experience injuries and had to be removed from training than horses that were able to complete the study (Figure 1).  All three treatment groups receiving the silicon source at a low, medium and high dosages had more horses complete the study without injury than were injured.  Furthermore, horses supplemented with the medium and high doses of silicon were able to train and race nearly twice the distance (an average of 90,438 and 82,928 meters respectively) before experiencing an injury than did the control group (49,503 meters; Figure 2).  Interestingly, the medium treatment group even had faster race times than did the control group at the middle race distance.  It is unlikely that the addition of silicon  made the horses faster.  Rather, it is probably that the faster horses were better able to withstand the rigors of racing, remain on the study, and increase the average speed of the whole group.  By contrast, it is likely the faster horses (the ones placing more load upon their skeleton) in the control group were injured and removed from the study leaving only the slower horses.

 

More studies were needed to try and determine what was causing the decreased injury rates.  At Michigan State University, recent studies demonstrated an increase in the concentration of a marker of bone formation in broodmares during the first 45 days after supplementation began when the mares foaled.  There was also a decrease in the concentrations of a marker of bone resorption by day 45 in yearlings after the beginning of supplementation.  At least in the mature animal, bone formation and resorption tend to be equal.  Hence, the amount of bone present tends to remain relatively constant.  If either bone formation increases or bone resorption decreases, researchers typically assume the result to be positive in regards to bone health.

 

Benefits of silicon to humans have also been shown.  Increased femoral density in osteoporotic women receiving absorbable silicon for four months has been reported.  The National Osteoporosis Society recently funded a large randomized, placebo-controlled clinical trial to determine if orthosilicic acid is a treatment for osteoporosis after a pilot study demonstrated silicon supplementation of osteoporotic postmenopausal women increased spinal bone mineral density by 3%.  The exact mechanism for enhanced bone metabolism, however, still needs to be determined.

 

Summary

 

Will feeding with bio-available silicon eliminate all injuries from one’s training program?  Obviously the answer is no.   Although the research that has been done thus far has clearly demonstrated a large decrease in the number of horses injured while being fed this substance, we will continue to research the role silicon plays in the health of bone and cartilage.  At this time, we can conclude that though proper training and good nutrition are still needed, supplementing horses with bioavailable silicon appears to be a promising method to aid in the prevention of injuries to equine athletes.

 

 

 

 

Figure 1.  Comparison by treatment of racing-related injuries in horses fed with  

Bio-available silicon

 

 

  

Figure 2.  Distance in meters to first failure (or completion of project if no injury occurred of horses fed  ^ab Treatment means not sharing the same superscript differ (p<.05)

 

References 

Benke, G.M., and T.W. Osborn. 1979. Urinary silicon excretion by rats following oral administration of silicon compounds. Food Cosmetics Tox. 17:123-127.

Calomme, M.R., and D.A. Vanden Berghe. 1997. Supplementation of calves with stabilized orthosilicic acid. Effect on the silicon, Ca, Mg, and P concentrations in serum and the collagen concentration in skin and cartilage. Biol. Trace Elem. Res. 56:153-165.

Carlisle, E.M. 1970. Silicon: A possible factor in bone calcification. Science 167:279.

Carlisle, E.M. 1972. Silicon: An essential element for the chick. Science. 178:619.

Carlisle, E.M. 1974. Silicon as an essential element. Fed. Proc.33:1758.

Carlisle, E.M. 1980a. A silicon requirement for normal skull formation in chicks. J. Nutr. 110:352.

Carlisle, E.M. 1980b. Biochemical and morphological changes associated with long bone abnormalities in silicon deficiency. J. Nutr. 110:1046.

Carlisle, E.M. 1982. The nutritional essentiality of silicon. Nutr. Reviews. 40(7):193.

Eisinger, J., and D. Clairet. 1993. Effects of silicon, fluoride, etidronate and magnesiliconum on bone mineral density: a retrospective study. Magnesiliconum Res. 6:247-249.

Lang, K.J., B.D. Nielsen, K.L. Waite, J. Link, G.M. Hill and M.W. Orth. 2001a. Increased plasma silicon concentrations and altered bone resorption in response to sodium zeolite A supplementation in yearling horses. J. Equine Vet. Sci. 21(11):550-555.

Lang, K.J., B.D. Nielsen, K.L. Waite, G.M. Hill and M.W. Orth. 2001b. Supplemental silicon increases plasma and milk silicon concentrations in horses. J. Anim. Sci. 79:2627-2633.

 

National Osteoporosis Society web-site. 2001. http://www.nos.org.uk/researchgrants.asp.

National Research Council. 1989. Nutrient Requirements of Horses. 5th ed., National Academy Press, Washington, DC.

Nielsen, B.D., G.D. Potter, E.L. Morris, T.W. Odom, D.M. Senor, J.A. Reynolds, W.B. Smith, M.T. Martin and E.H. Bird. 1993. Training distance to failure in young racing Quarter Horses fed sodium zeolite A. J. Equine Vet. Sci. 13(10):562.

Nielsen, F.H. 1991. Nutritional requirements for boron, silicon, vanadium, nickel, and arsenic: current knowledge and speculation. FASEB J. 5:2661-2667.

Pennington, J.A.T. 1991. Silicon in foods and diets. Food Add. Contam. 8(1):97-118.

Reeves, P.G. 1997. Components of the AIN-93 diets as improvements in the AIN-76A diet. J. Nutr. 127:838S-841S.

Van Soest, P.J., M.S. Allen and M.I. McBurney. 1983. Silicon, chromium, the rare earth elements and the remainder of the periodic table. Nat. Feed Ingred. Assoc. Nutr. Inst. Program. April 4-7, Chicago, IL.