Understanding Silica Bioavailability
Bioavailability refers to the proportion of a nutrient that is absorbed and utilized by the body. For silica, the key factor influencing absorption is its chemical structure and whether it exists in a monomeric (single-molecule) or polymeric (chain of molecules) form. The small, uncharged monomeric species, such as orthosilicic acid (OSA), are readily absorbed in the gastrointestinal tract, while larger, polymerized, or colloidal forms are poorly absorbed. However, OSA is unstable at high concentrations and can polymerize, which is why stabilized forms are often used in supplements.
The Best-Absorbed Silica Forms
Monomethylsilanetriol (MMST)
Independent studies have consistently shown monomethylsilanetriol (MMST) to be one of the most bioavailable forms of silica available on the market, with an absorption rate reported as high as 64%. MMST is a stabilized, monomeric form of silicon that remains soluble and stable in solution, preventing it from polymerizing into less absorbable compounds. Upon absorption, MMST is converted into the biologically active orthosilicic acid within the body. This makes MMST an excellent option for supplementing silicon intake effectively.
Stabilized Orthosilicic Acid (OSA)
Naturally occurring orthosilicic acid (OSA) is highly bioavailable, but its instability at higher concentrations is a challenge for supplementation. To overcome this, manufacturers stabilize OSA using compounds like choline (ch-OSA) or maltodextrin (M-OSA) to prevent polymerization and maintain its absorbable monomeric form. Clinical studies have shown that stabilized OSA is a readily absorbed and effective source of silicon. Choline-stabilized orthosilicic acid, for example, has demonstrated a significant increase in serum and urinary silicon levels, confirming its superior bioavailability over many other forms.
Silicon-Rich Mineral Water
Drinking water, especially from mineral-rich sources, contains naturally dissolved orthosilicic acid, which is in a highly absorbable state. Studies have shown that a significant portion of silicon from mineral water is readily absorbed. Some research suggests that consuming silicon-rich mineral water can even help reduce the body's burden of aluminum by facilitating its removal through urine. This makes mineral water a simple, accessible way to boost dietary silicon intake with high bioavailability.
Less Bioavailable Silica Forms
Colloidal Silica
Colloidal silica consists of ultrafine particles, but studies have demonstrated that its bioavailability is very low, often around 1-7%. These forms tend to exist in a polymerized or aggregated state, which the body struggles to break down and absorb effectively through the intestinal lining. Therefore, supplements based on colloidal silica are generally not recommended for optimal absorption.
Horsetail and Bamboo Extracts
While horsetail (Equisetum arvense) and bamboo (Bambusa vulgaris) are rich botanical sources of silica, their extracts often have low bioavailability. The silica in these plants is typically found in a highly polymerized form, which is not easily absorbed. The absorption rate can be as low as 3-8% for horsetail-derived supplements. Although some products are processed to increase the absorbable silicon content, their efficacy is often significantly lower compared to MMST or stabilized OSA.
Diatomaceous Earth
Food-grade diatomaceous earth is primarily composed of amorphous silica. While it contains a high percentage of silica, it is largely insoluble and poorly absorbed. While some suggest it is converted to OSA in the body, evidence regarding its human bioavailability is limited and it is presumed to be similar to other poorly absorbed forms.
Comparison of Silica Forms
| Feature | Monomethylsilanetriol (MMST) | Stabilized Orthosilicic Acid (OSA) | Horsetail / Bamboo Extracts | Colloidal Silica | Diatomaceous Earth |
|---|---|---|---|---|---|
| Absorption Rate | Highest (approx. 64%) | High (approx. 17-43%) | Low (approx. 3-8%) | Very Low (approx. 1-7%) | Low |
| Molecular Form | Monomeric and stable | Monomeric (when stabilized) | Highly polymerized | Highly polymerized/aggregated | Amorphous, highly polymerized |
| Stability | Highly stable in solution | Stable only at low concentrations unless stabilized | Stable but poorly soluble | Unstable; tends to aggregate | Insoluble |
| Best For | Maximum bioavailability and effectiveness | Reliable absorption with good stability | Those seeking natural sources, though absorption is limited | Not recommended for high absorption | Limited research on human absorption |
How to Optimize Your Silica Intake
- Prioritize MMST or Stabilized OSA Supplements: For the highest absorption, choose supplements containing either monomethylsilanetriol or a stabilized form of orthosilicic acid. These are specifically formulated to remain in the small, monomeric state that the body can effectively utilize. For example, brands often advertise choline-stabilized orthosilicic acid (ch-OSA) for its proven bioavailability.
- Rely on Diet for Natural OSA: Include silica-rich foods in your diet, but understand that the bioavailability varies. The silicon present as orthosilicic acid in beverages like water and beer is readily absorbed. While plant sources like oats, green beans, and leafy greens contain silica, some of it is in a poorly absorbed, polymerized form.
- Be Wary of Low-Bioavailability Forms: Exercise caution with supplements containing ingredients like horsetail extract, colloidal silica, or diatomaceous earth if your primary goal is maximum absorption. Though sometimes marketed as potent, studies show their bioavailability is significantly lower.
- Consider Dosage: Follow the recommended daily intake on reputable supplements. For many high-bioavailability forms like stabilized OSA, effective dosages are often in the 5-10 mg per day range. It's the form, not just the quantity, that dictates effectiveness.
Conclusion
Not all silica supplements are created equal when it comes to absorption. The chemical form of the silica is the most critical factor, with monomeric and water-soluble species being far superior to polymerized or colloidal types. For individuals seeking the best absorption to support bone, skin, hair, and nails, monomethylsilanetriol (MMST) and stabilized orthosilicic acid (OSA) are the most effective supplemental options. While natural sources like mineral water are also beneficial, the silicon in plant extracts and other common supplement forms is often poorly absorbed. By understanding the science of bioavailability, consumers can make informed choices to ensure they get the most from their silica supplement. For more information on the bioavailability of dietary supplements, consult authoritative sources like the National Institutes of Health.
