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Solid foods are a major source of available silicon. The association between dietary silicon intake and bone health should now be investigated.

The role of dietary silicon in bone health in humans is not known. In a cross-sectional, population-based study (2847 participants), associations between dietary silicon intake and BMD were investigated. Dietary silicon correlated positively and significantly with BMD at all hip sites in men and premenopausal women, but not in postmenopausal women, suggesting that increased silicon intake is associated with increased cortical BMD in these populations.Introduction: Osteoporosis is a burgeoning health and economic issue. Agents that promote bone formation are widely sought. Animal and cellular data suggest that the orthosilicate anion (i.e., dietary silicon) is involved in bone formation. The intake of silicon (Si, ϳ30 mg/day) is among the highest for trace elements in humans, but its contribution to bone health is not known. Materials and Methods:In a cross-sectional, population-based study, we examined the association between silicon intake and bone mineral density (BMD) in 1251 men and 1596 pre-and postmenopausal women in the Framingham Offspring cohort (age, 30 -87 years) at four hip sites and lumbar spine, adjusting for all potential confounding factors known to influence BMD and nutrient intake. Results: Silicon intake correlated positively with adjusted BMD at four hip sites in men and premenopausal women, but not in postmenopausal women. No significant association was observed at the lumbar spine in any group. Categorical analysis by Si intake, or energy-adjusted Si intake, supported these findings, and showed large differences in BMD (up to 10%) between the highest (Ͼ40 mg Si/day) and lowest (Ͻ14 mg Si/day) quintiles of silicon intake. A significant association at the lumbar spine in men was also observed. Further analyses indicated that some of the effects seen for moderate consumption of alcoholic beverages on BMD might be attributed to Si intake. Conclusions: These findings suggest that higher dietary silicon intake in men and younger women may have salutary effects on skeletal health, especially cortical bone health, that has not been previously recognized. Confirmation of these results is being sought in a longitudinal study and by assessment of the influence of silicon intake on bone markers in this cohort.

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Dietary Si (orthosilicic acid; OSA) appears important in connective tissue health, and although the sources and intakes of Si are well established, its absorption is not. Si absorption was measured from eight high-Si-containing sources: alcohol-free beer; OSA solution (positive control); bananas; green beans; supplemental choline-stabilised OSA (ChOSA); supplemental monomethyl silanetriol (MMST); supplemental colloidal silica (CS); magnesium trisilicate British Pharmacopoeia antacid (MTBP). Two of the supplements and the antacid were pre-selected following an in vitro dissolution assay. Fasting, healthy subjects (CS, n 3; others, n $ 5) each ingested two of the sources separated by a 1-week wash-out period. Blood and urine were collected and measured for total Si concentrations by inductively coupled plasma optical emission spectrometry. Absorption, based on urinary Si excretion, was highest for MMST and alcohol-free beer (64 % of dose), followed by green beans (44 %), OSA (43 %), ChOSA (17 %), bananas and MTBP (4 %) and CS (1 %). Peak serum concentrations occurred by 0.5 h for MMST and green beans, 1.5 h for OSA and alcohol-free beer, 2 h for ChOSA and CS, and 4 h for MTBP. Area under the serum curves correlated positively with urinary Si output (r 0·82; P,0·0001). Absorption of Si from supplements and antacids was consistent with their known chemical speciation and kinetics of dissolution under simulated gastrointestinal conditions. Monomeric silicates were readily absorbed, while particulate silicates were decreasingly well absorbed with increasing polymerisation. The present results highlight the need to allow for relative absorption of Si from different foods or supplements in subsequent epidemiological and intervention studies.

Silicon-deficiency studies in growing animals in the early 1970s reported stunted growth and profound defects in bone and other connective tissues. However, more recent attempts to replicate these findings have found mild alterations in bone metabolism without any adverse health effects. Thus the biological role of silicon remains unknown. Using a specifically formulated silicon-depleted diet and modern methods for silicon analysis and assessment of skeletal development, we undertook, through international collaboration between silicon researchers, an extensive study of long-term silicon depletion on skeletal development in an animal. 21-day old female Sprague–Dawley rats (n = 20) were fed a silicon-depleted diet (3.2 µg Si/g feed) for 26 weeks and their growth and skeletal development were compared with identical rats (n = 10) on the same diet but with silicon added as Si(OH)4 to their drinking water (53.2 µg Si/g water); total silicon intakes were 24 times different. A third group of rats, receiving a standard rodent stock feed (322 µg Si/g feed) and tap water (5 µg Si/g water), served as a reference group for optimal growth. A series of anthropometric and bone quality measures were undertaken during and following the study. Fasting serum silicon concentrations and especially urinary silicon excretion were significantly lower in the silicon-deprived group compared to the supplemented group (P = 0.03 and 0.004, respectively). Tibia and soft-tissue silicon contents did not differ between the two groups, but tibia silicon levels were significantly lower compared to the reference group (P < 0.0001). Outward adverse health effects were not observed in the silicon-deprived group. However, body lengths from week 18 onwards (P < 0.05) and bone lengths at necropsy (P ≤ 0.002) were longer in this group. Moreover, these measures correlated inversely with serum silicon concentrations (P ≤ 0.02). A reduction in bone growth plate thickness and an apparent increase in chondrocyte density were also observed in the silicon-deprived animals. No other differences were observed between the two groups, except for tibia phosphorus concentrations, which were lower in the silicon-deprived animals (P = 0.0003). Thus in this study we were unable to reproduce the profound deficiency state reported in rats and chicks in the early 1970s. Indeed, although silicon intake and circulating fasting serum levels differed between the silicon-deprived and silicon-supplemented animals, tibia and soft-tissue levels did not and may explain the lack of difference in bone quality and bone markers (except serum CTx) between these two groups. Markedly higher tibia silicon levels in the reference group and nutritional differences between the formulated low-Si and reference diets suggest that one or more co-factors may be absent from the low-Si diet that affect silicon incorporation into bone. However, evidence for urinary silicon conservation (to maintain tissue levels), changes in bone/body lengths, bone calcium:phosphorus ratio and differences at the gro...

Si may play an important role in bone formation and connective tissue metabolism. Although biological interest in this element has recently increased, limited literature exists on the Si content of foods. To further our knowledge and understanding of the relationship between dietary Si and human health, a reliable food composition database, relevant for the UK population, is required. A total of 207 foods and beverages, commonly consumed in the UK, were analysed for Si content. Composite samples were analysed using inductively coupled plasma-optical emission spectrometry following microwave-assisted digestion with nitric acid and H 2 O 2 . The highest concentrations of Si were found in cereals and cereal products, especially less refined cereals and oat-based products. Fruit and vegetables were highly variable sources of Si with substantial amounts present in Kenyan beans, French beans, runner beans, spinach, dried fruit, bananas and red lentils, but undetectable amounts in tomatoes, oranges and onions. Of the beverages, beer, a macerated whole-grain cereal product, contained the greatest level of Si, whilst drinking water was a variable source with some mineral waters relatively high in Si. The present study provides a provisional database for the Si content of UK foods, which will allow the estimation of dietary intakes of Si in the UK population and investigation into the role of dietary Si in human health.

Dietary Si, as soluble orthosilicic acid (OSA), may be important for the growth and development of bone and connective tissue. Beer appears to be a major contributor to Si intake, although the Si content of beer and its bioavailability in human subjects have not been well established. Here we investigated the Si content of different beers and then estimated Si absorption from beer in healthy volunteers. The Si content of seventy-six different beers was estimated using inductively coupled plasma optical emission spectrometry and one of the beers, used in the ingestion study, was ultrafiltered to determine OSA content. Next, following the ingestion of 0·6 litres beer (22·5 mg Si; 4·6 % (v/v) ethanol), serum and urinary Si levels were measured in nine healthy volunteers over a 6 h period. A solution of OSA was similarly investigated as a positive control and water and 4·6 % ethanol as negative controls. The mean Si level of beer was 19·2 (SD 6·6) mg/l; the median Si level was 18·0 mg/l. There was no significant difference in the Si levels of the different beers by geographical origin or type of beer. Serum and urinary Si levels increased considerably following the ingestion of beer or a solution of OSA but not with the ingestion of either 4·6 % ethanol or water. The ultrafilterability of Si from beer (about 80 %) and its absorption in volunteers (about 55 %) was comparable with that of a solution of OSA suggesting that Si in beer is present chiefly in a monomeric form and is readily bioavailable.