Silica, or silicon dioxide, is the form of dietary silicon found in foods. Silicon is a trace mineral naturally present in all human tissues, with concentrations highest in connective tissues and bone. While the body needs only small amounts, this mineral is considered an important component for maintaining biological structures. The majority of our intake comes from plant-based foods that absorb silicon from the soil as they grow.
Role of Silicon in Human Health
Silicon plays a direct role in the maintenance and formation of the body’s connective tissues. This is achieved through its involvement in the synthesis of both collagen and elastin, which provide structure and flexibility. The presence of silicon promotes cross-linking between collagen and proteoglycans, reinforcing the connective tissue matrix.
The mineral is also structurally integrated into bone health, working alongside calcium and other minerals. Silicon helps regulate the process of bone mineralization by assisting in the formation of bone-building cells known as osteoblasts. Studies suggest that adequate silicon intake is associated with higher bone mineral density, supporting the structural integrity of the skeleton. Because it is involved in collagen formation, silicon supports the health of skin, hair, and nails, which are all rich in these structural proteins.
Grains, Vegetables, and Herbs Rich in Silica
Dietary silicon is abundant in unrefined plant-based foods that absorb the mineral from the soil. Whole grains are particularly rich sources, with oats and barley containing high concentrations of silicon, especially in their husks. Unrefined grain products, such as whole wheat flour and brown rice, contain higher levels of the mineral compared to refined counterparts.
Certain vegetables and fruits also contribute to daily silicon intake. Significant food sources include:
- String beans and green beans
- Bananas
- Root vegetables like carrots and beets
- Leafy greens such as spinach and asparagus
Herbal sources contain some of the highest recorded concentrations of silicon, often concentrated enough to be used in supplements. The herb horsetail, or Equisetum arvense, is notable for its ability to concentrate the mineral in the form of silicic acid. Nettle leaf is another herb that naturally contains elevated levels of dietary silicon.
Bioavailability and Maximizing Dietary Intake
The amount of silicon the body can absorb, known as bioavailability, varies significantly depending on the food source. Silicon must be converted into a water-soluble compound called orthosilicic acid (OSA) for efficient absorption in the gut. Monomeric orthosilicic acid is the most readily absorbed form, with absorption rates potentially reaching up to 50%.
For solid foods, total silicon content does not always reflect how much the body uses. For example, while bananas have high mineral content, the silicon they contain is poorly absorbed, with estimates as low as 5%. In contrast, silicon from green beans has an estimated absorption rate of about 44%. Beverages can also be a significant source of absorbable silicon, with beer often showing a high absorption rate of up to 64%.
Drinking water is a primary source of dietary silicon, though the concentration varies widely based on the geographical source and mineral content. To maximize intake from solid foods, choosing less-processed options is beneficial, as refining and processing can lead to a loss of up to 50% of the mineral content.