Boron is an ultratrace, non-metallic mineral naturally distributed across the globe. It is definitively recognized as an essential nutrient for plants, playing a structural part in cell walls and being needed for reproduction and seed formation. Although not yet classified as an essential nutrient for humans, research indicates boron may offer beneficial effects on bone health, brain function, and the metabolism of other minerals and hormones.
Boron in the Environment and Water Systems
Boron is the 51st most common element found in the Earth’s crust, typically present at about eight milligrams per kilogram. It does not exist as a pure element but is always bound to oxygen, forming various borate minerals and compounds. Significant geological sources include borax, kernite, and ulexite, which are concentrated in sedimentary deposits, particularly in arid regions.
The natural weathering of these minerals slowly releases the element into the soil and water systems. This process, along with the decomposition of organic matter, is the primary way boron enters the environmental cycle. Regions with high rainfall often have lower soil boron concentrations because water leaches the mineral out of the topsoil, contrasting with arid areas like parts of Turkey, Argentina, and California.
Boron concentrations in water sources vary considerably depending on local geology and human activities. The average surface water concentration in the United States is around 0.1 milligrams per liter, but this can range widely. Ocean water maintains a relatively consistent boron concentration, typically averaging around 4.5 milligrams per liter.
The solubility of borate minerals means that once boron compounds dissolve, they are easily transported through water, making removal difficult. Freshwater sources, including groundwater and drinking water, show significant variability. Water that has interacted with geothermal activity or specific geological formations can naturally exhibit much higher levels.
Primary Dietary Sources of Boron
The concentration of boron in foods is directly influenced by the amount present in the soil and water where the food was grown. Plant-based sources consistently contain the largest amounts of boron, reflecting its status as an essential micronutrient for plant life. The highest concentrations are generally found in fruits, vegetables, nuts, and legumes, where plant cell walls act as a storage location.
High-Boron Foods
Dried fruits are particularly concentrated sources, providing substantial amounts of the mineral per serving. Raisins, prunes, and dried apricots are excellent examples. Raisins can contain around 4.5 milligrams of boron per 100 grams, making them one of the richest dietary sources, and prune juice offers over one milligram per cup.
Nuts and legumes also contribute significantly to intake, with almonds, hazelnuts, and peanuts being excellent sources. Specific vegetables, such as red kidney beans, avocados, and potatoes, also contain appreciable amounts. The boron found in these foods is present as inorganic borates or sugar-borate esters, which are readily absorbed by the body.
Intake and Preparation
Food preparation can affect the final boron content consumed. Processing techniques like cooking or peeling may alter the mineral’s retention in some foods. Daily boron intake is highly dependent on food choices, but a diet rich in fruits and vegetables generally provides between 1.5 and 3.0 milligrams per day.
Beverages contribute a significant portion of daily boron intake, including coffee, wine, cider, and beer. Although a single cup of coffee contains a small amount, frequent consumption can accumulate a large portion of intake from this source. Plant foods remain the most reliable way to obtain this trace mineral through diet.
Commercial and Supplemental Sources
Beyond natural food and water, boron is encountered in various commercial products and dietary supplements. The primary supplemental forms are often boric acid or sodium borate, used by individuals seeking to increase their intake. These supplements are typically sought for potential benefits related to bone health, joint support, and hormone metabolism.
Supplements and Bioavailability
The elemental boron content listed on a supplement label refers to the weight of the pure element, not the entire compound. The body efficiently absorbs about 85% to 90% of ingested boron, though the exact bioavailability of different supplemental forms can vary. Supplemental doses for adults often stay below the established upper intake level of 20 milligrams per day.
Industrial and Agricultural Uses
Boron is extensively used in a wide array of non-dietary commercial applications. Boron compounds are fundamental in manufacturing processes for glass, particularly heat-resistant borosilicate glass. They are also incorporated into fire retardants and ceramic glazes.
Boron compounds are widely used in detergents, bleaches, and other cleaning agents. This application can result in boron being released into wastewater, impacting environmental concentrations in surface waters. Furthermore, boron is an ingredient in agricultural fertilizers, added to the soil to ensure adequate nutrition for crops in deficient regions.