Is Silicon Really Essential?
Since the 1970s, research has provided increasing evidence that silicon plays a key role in human health. Despite this, an official Recommended Dietary Allowance (RDA) has not yet been established for silicon in humans, largely because definitive proof of its requirement for reproduction or completion of the life cycle has been lacking. However, deficiency studies in animals have shown marked defects in bone and connective tissue development, suggesting its importance. The body contains approximately 7 grams of silicon, the third most abundant trace element, found primarily in connective tissues, skin, bones, and arteries.
The Critical Role of Silicon in Human Health
Silicon's function is centered on supporting the body's structural components, particularly through its involvement in creating and maintaining connective tissues.
- Bone Formation and Mineralization: Silicon is required for the synthesis of the collagen matrix upon which calcium is deposited to form bone. It is highly concentrated in immature bone tissue and helps regulate the deposition of calcium and phosphorus. Studies in both animals and humans link higher dietary silicon intake to increased bone mineral density, especially in men and premenopausal women.
- Connective Tissue and Collagen Synthesis: Silicon is a critical component for the synthesis of collagen and elastin, proteins that provide strength and flexibility to various connective tissues like skin, hair, nails, cartilage, tendons, and blood vessels. Without sufficient silicon, collagen synthesis and cross-linking can be impaired.
- Protection Against Aluminum Toxicity: Some research suggests that silicon intake can help protect against aluminum toxicity by forming a bond with aluminum, which reduces its bioavailability and absorption in the body. This is a potential benefit noted in studies concerning Alzheimer's disease.
Comparing Different Silicon Forms and Bioavailability
Not all forms of silicon are equally absorbed by the human body. The form and solubility of silicon have a major impact on its bioavailability, which is the proportion of a nutrient that is absorbed from the diet and used for metabolic functions.
| Feature | Orthosilicic Acid (OSA) | Polymeric Silica (e.g., in solid foods) | Silicon Dioxide (E551) |
|---|---|---|---|
| Natural Occurrence | Found in fluids like mineral water and beer. | Found in plants, such as cereals and bananas, as phytoliths. | Found naturally, but also used as an additive. |
| Chemical State | Soluble, monomeric form. | Less soluble, highly polymerized form. | Generally considered an inert solid. |
| Bioavailability | High absorption rate (e.g., up to 55% from beer). | Poor absorption, with much being excreted. | Very limited absorption from the gut. |
| Absorption Mechanism | Readily diffuses across the gut lining. | Requires hydrolysis in the gut, which can be inefficient. | Passes through largely unabsorbed when ingested. |
How to get enough dietary silicon
Since the absorption of silicon is dependent on its form, consuming a balanced diet rich in varied sources is the most reliable way to maintain adequate levels. Daily intakes for Western diets typically range from 20 to 50 mg.
Best food sources of bioavailable silicon:
- Cereal grains: Whole grains, oats, barley, and millet are excellent sources of absorbable silicon. Wholemeal products are generally higher in silicon than their refined counterparts.
- Beverages: Beer, due to its barley and hops content, is a surprisingly rich and highly bioavailable source. Mineral and spring waters can also contribute significantly, depending on their geological source.
- Vegetables: Green beans, lentils, leafy greens, and root vegetables like carrots and potatoes are good sources.
- Fruits and Dried Fruits: Bananas and raisins are noted as higher silicon sources. However, the bioavailability from bananas is low, so they contribute less available silicon than might be expected.
- Seafood: Mussels and other seafood can also contain noteworthy levels.
Potential Risks and Important Considerations
For healthy individuals with normal kidney function, dietary intake of silicon is generally considered safe, as the body effectively excretes excess amounts in urine. High-level inhalation of crystalline silica dust, however, poses a significant health risk, leading to lung diseases like silicosis. This should not be confused with dietary intake. Some studies have raised concerns about nanoparticles in food additives like silicon dioxide (E551), prompting some regulatory bodies to call for further research, though its ingestion in food is generally not considered dangerous.
Conclusion
While silicon may not yet be an officially designated essential nutrient for humans, a compelling body of research demonstrates its importance for multiple physiological processes. From strengthening bones and synthesizing collagen for connective tissues to potentially mitigating aluminum toxicity, adequate dietary silicon intake provides meaningful health benefits. The best approach is to consume a balanced diet rich in whole grains, certain vegetables, and mineral water. For most people, this is enough to obtain a beneficial daily intake, as the body is highly efficient at regulating and excreting excess absorbed silicon. Consumers should be mindful of the different bioavailability of silicon forms, opting for less processed, whole foods where possible.
