Life Extension Magazine April 2003
Silicon: An Overlooked
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, glucosomine 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 Schwarz1,2 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 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, silicion 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.
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