Journal of Trace Elements in Medicine and Biology
REVIEWUPDATE ON THE POSSIBLE NUTRITIONAL IMPORTANCE OF SILICON☆
Introduction
Silicon is nutritionally essential for some lower forms of life [1]. Silicon has a structural role in diatoms, radiolarians, and some sponges. Diatoms, which are unicellular microscopic plants, have an absolute requirement for silicon as monomeric silicic acid for normal cell growth. Silicon also may be essential for some higher plants (e.g., rice). Because silicon deprivation has not been shown to interrupt the life cycle in mammals, or to have a defined biochemical function, silicon is not generally accepted as an essential nutrient for higher animals and humans. However, for over 40 years, reports about silicon having beneficial, especially on connective tissue and bone formation, in higher animals and humans have appeared. Initial experiments performed in the 1970s used supra nutritional supplemental amounts of silicon (100 and 500 mg/kg diet) to prevent abnormalities in animal models fed low-silicon diets of questionable nutritional quality based on growth data. The silicon supplementation alleviated abnormal bone structure and strength in chicks and rats; abnormal bone cartilage characterized by decreased hexosamine in chicks; and decreased collagen and prolyhydroxylase activity in skull bone from cultured chick embryos [1], [2]. Concern about dietary quality resulted in the question of whether the supra nutritional supplements were alleviating abnormalities caused by a silicon deprivation or induced by some other sub-optimal dietary factor.
Section snippets
Silicon, bone and connective tissue
Experiments performed since 2000 have indicated that only nutritional amounts of silicon are needed to prevent bone, hexosamine, and collagen metabolism abnormalities, similar to, but of less magnitude than those reported in the 1970s, in animal models fed apparently nutritionally-adequate diets low in silicon. In three studies, silicon supplementation of 10 or 35 mg/kg diet containing < 2.0 mg/kg silicon, was used to show that the silicon deprivation in rats decreased collagen formation [3] and
Silicon and immune and inflammatory response
In 1988, it was suggested that silicon had a regulatory role in the cell cycle of lymphocytes because monomethylsilanetriol at an optimal concentration of 10 mg/L silicon in culture media stimulated peripheral lymphocyte proliferation and decreased lymphoblast proliferation [22]. This possible effect of silicon in nutritional amounts received little attention until 2002 when it was reported that mitogen-induced DNA synthesis of splenic T-lymphocytes from silicon deprived (2.3 mg/kg diet) compared
Silicon and mental health
In 1996, it was reported that an association between cognitive impairment and aluminum in drinking water depended upon the silica concentration in water [26]. High levels of aluminum appeared to have a deleterious effect on cognitive function when the silica concentration was low, and high silica concentrations had a protective effect on the association between high aluminum and impaired cognitive function. In 2000, it was reported that the 8-year follow-up of subjects in the Paquid cohort
Plausible silicon mechanism of action
A plausible biochemical mechanism of action for silicon is some type of structural or binding role that affects the formation of connective tissue where it is strongly bound in significant concentrations [1], [2]. This binding role is supported by the finding that silicon easily forms stable complexes with polyols that have at least four hydroxyl groups [31]. Such polyols include hexosamine and ascorbate used to form glycosaminoglycans, mucopolysaccharides, and collagen involved in connective
Silicon metabolism
Several recent studies of silicon have involved its dietary intake, absorption, transport, retention, and excretion. These studies suggest that silicon may have a significant role in higher animals and humans because silicon is well regulated by the body. Silicon is relatively well absorbed when consumed from various foods and drinks. One study found an average of 41% of silicon in food was excreted in urine, which is an indicator of absorption [35]. A study determining the absorption of
Silicon status indicators
Because reported fasting serum concentrations range from 10 to 31 μg/dL, concentrations in the lower part or below this range might be an indication of a suboptimal silicon status. In addition, a consistent urinary silicon excretion below 14 mg/d may be indicating that an individual has a suboptimal intake of silicon because this excretion compared with 40 mg/d was associated with decreased bone mineral density in humans [15]. This finding also suggests that there is a dose-response to silicon for
Beneficial intakes of silicon
On the basis of extrapolations from animal data, weak balance data from humans, and the usual amount of silicon excreted daily by humans, it has been suggested that an adequate intake to achieve the beneficial effects of silicon might be between 10 to 25 mg/d [39]. Based on the findings from 1251 men and 1596 pre- and postmenopausal women in the Framingham Offspring Cohort, the beneficial intake most likely is near the 25 mg/d intake or slightly higher. The majority of the intakes in this cohort
Conclusion
Recent findings provide additional evidence that silicon in nutritional amounts is beneficial for bone growth and maintenance. In addition, silicon in nutritional amounts might have a beneficial effect in the immune or inflammatory response and in mental health. Supra nutritional amounts of silicon also may promote bone health. Plausible mechanisms of actions have been suggested for the beneficial effects of silicon. Recent epidemiological findings suggest that intakes near 25 mg/d might promote
References (40)
- et al.
Increased longitudinal growth in rats on a silicon-depleted diet
Bone
(2008) - et al.
Effects of calcium sources and soluble silicate on bone metabolism and the related gene expression in mice
Nutrition
(2009) - et al.
Orthosilicic acid stimulates collagen type 1 synthesis and osteoblastic differentiation in human osteoblast-like cells in vitro
Bone
(2003) - et al.
Silica-based bioactive glasses modulate expression of bone morphogenetic protein-2 mRNA in Saos-2 osteoblasts in vitro
Biomater
(2001) - et al.
Effects of beer, wine, and liquor intakes on bone mineral density in older men and women
Am J Clin Nutr
(2009) - et al.
Dietary silicon interacts with oestrogen to influence bone health: Evidence from the Aberdeen Prospective Osteoporosis Screening Study
Bone
(2012) A novel silicon complex is as effective as sodium metasilicate in enhancing the collagen-induced inflammatory response of silicon-deprived rats
J Trace Elem Med Biol
(2008)- et al.
Cognitive impairment and composition of drinking water in women: findings of the EPIDOS study
Am J Clin Nutr
(2005) - et al.
Silicon facilitation of copper utilization in the rat
J Nutr Biochem
(1990) - et al.
Dietary intake and absorption
Am J Clin Nutr
(2002)
Dietary silicon intake in Belgium: sources, availability from foods, and human serum levels
Sci Total Environ
Reference values for serum silicon in adults
Anal Biochem
Silicon
Significance and function of silicon in warm-blooded animals. Review and outlook
Silicon deprivation decreases collagen formation in wounds and bone, and ornithine transaminase enzyme activity in liver
Biol Trace Elem Res
Silicon deprivation and arginine and cystine supplementation affect bone collagen and bone and plasma trace mineral concentrations in rats
J Trace Elem Exp Med
Dietary silicon affects bone turnover differently in ovariectomized and sham-operated growing rats
J Trace Elem Exp Med
Bioactive glasses for in situ tissue regeneration
J Biomater Sci Polymer Ed
Effect of silicon supplement on osteopenia induced by ovariectomy in rats
Calcif Tissue Int
Silicon supplementation improves the bone mineral density of calcium-deficient ovariectomized rats by reducing bone resorption
Biol Trace Elem Res
Cited by (0)
- ☆
The U.S. Department of Agriculture, Agricultural Research Service, Northern Plains Area, is an equal opportunity/affirmative action employer and all agency services are available without discrimination.