The Importance of Bioavailability
Silicon is the second most abundant element in the Earth's crust, but its availability for human absorption, or bioavailability, is highly dependent on its chemical form. For silica to be absorbed by the body, it must be in a small, soluble, monomeric form, such as orthosilicic acid (OSA). Larger, polymerized or colloidal forms are much less bioavailable and pass through the digestive system largely unabsorbed. This fundamental chemical principle is the most important factor in determining what increases silica absorption.
Dietary and Supplemental Forms for Increased Absorption
Orthosilicic Acid (OSA)
OSA is the most readily absorbed form of silicon, found naturally in beverages like water and beer. The silicon in mineral waters, for instance, is already in this soluble form, making it easy for the body to absorb. Beer also contains bioavailable OSA due to the breakdown of silica from barley and hops during the brewing process.
Choline-Stabilized Orthosilicic Acid (ch-OSA)
Since pure OSA is unstable and tends to polymerize into poorly absorbed forms at higher concentrations, supplements use stabilizing agents. Choline is a common stabilizer that forms hydrogen bonds with OSA, preventing polymerization and ensuring high bioavailability. Studies have shown ch-OSA to significantly increase serum silicon levels. Choline itself is an essential nutrient and plays a role in metabolism, potentially offering additional benefits.
Monomethylsilanetriol (MMST)
MMST is another highly absorbable form of silicon used in supplements. It has one of the highest absorption rates compared to other supplemental forms, due to its chemical structure that maintains solubility.
Phytolithic Silica from Whole Grains
Plants absorb OSA from the soil and deposit it as solid, amorphous silica known as phytoliths, especially in the husks of grains. While not as immediately bioavailable as OSA in liquids, the silicon from whole grains like oats, barley, and rice is still a significant dietary source. The digestive system can break down these phytoliths, though less efficiently than absorbing soluble OSA. This is why whole grain products offer moderate silicon absorption.
Factors that Inhibit Silica Absorption
Several factors can decrease silica bioavailability:
- Polymerization: As discussed, larger, polymerized forms of silica (like in bananas) have very low absorption rates. Some low-quality supplements and food additives containing silicon dioxide also fall into this category.
- High Fiber Diet: Studies have shown that diets high in fiber, particularly from fruits and vegetables, can reduce the gastrointestinal uptake of minerals, including silicon. However, the overall nutritional benefits of fiber typically outweigh this effect.
- Other Mineral Interactions: High dietary levels of cations like calcium and magnesium may compete for absorption pathways with silicon. Some research suggests calcium may form insoluble silicates, further reducing bioavailability.
- Age and Gastric Acidity: With aging, a reduction in gastric acid output can impair the body's ability to process and absorb dietary silica effectively.
Maximizing Your Intake
To improve your silica absorption, consider incorporating a variety of sources into your diet. This can involve combining different food types and being mindful of the form of silica you are consuming.
Comparison Table: Silica Sources and Bioavailability
| Source | Silicon Form | Absorption Rate | Comments |
|---|---|---|---|
| Mineral Water | Soluble Orthosilicic Acid (OSA) | High (>50%) | Highly bioavailable and readily absorbed. |
| Beer | Soluble Orthosilicic Acid (OSA) | High (~55%) | Derived from barley and hops during brewing. |
| Whole Grains (Oats, Barley) | Phytolithic Silica | Moderate | Requires digestion, but a major dietary source. |
| Green Beans | Phytolithic Silica | Moderate | Bioavailability is intermediate compared to water and bananas. |
| Bananas | Highly Polymerized Silica | Very Low (~4%) | Polymerized form is difficult to absorb. |
| Choline-Stabilized OSA (ch-OSA) | Stabilized Orthosilicic Acid | High (up to ~40%) | Prevents polymerization for better absorption. |
| Monomethylsilanetriol (MMST) | Stabilized Silicon | High (~64%) | Very high bioavailability, often used in supplements. |
| Supplemental Colloidal Silica | Large Colloidal Particles | Very Low (~1%) | Poorly absorbed by the body. |
Tips for Better Absorption
- Prioritize Soluble Forms: Focus on getting silica from beverages like water and beer, as these offer the most readily absorbed OSA.
- Combine with Other Nutrients: Ensure adequate intake of other minerals and vitamins essential for bone and connective tissue health, such as vitamin D, calcium, and magnesium. While high levels of some minerals can interfere, a balanced diet with recommended intake levels is synergistic. Find more information on the role of silicon in human biology on this Frontiers in Plant Science article.
- Choose Whole Foods: Opt for unrefined whole grains over processed alternatives, as processing removes the silicon-rich husks.
- Consider Supplements: If your diet is low in natural, bioavailable sources, high-quality supplements containing MMST or ch-OSA can be a reliable option. Always consult a healthcare provider before starting new supplements.
Conclusion
What increases silica absorption is fundamentally linked to the form in which it is consumed. The more soluble and monomeric the form, the higher the bioavailability. Orthosilicic acid, found in certain waters and beverages, is the gold standard for natural absorption. For those seeking supplemental options, stabilized forms like ch-OSA and MMST offer high bioavailability by preventing polymerization. While dietary factors like high fiber or mineral imbalances can interfere, a balanced diet rich in whole foods and fluids remains the best strategy for maintaining optimal silica levels. By making informed choices about sources and forms, you can significantly enhance your body's utilization of this vital trace mineral.
