Boron is a metallic element that was discovered in 1808. Only since about 1980 has boron begun to be recognized as a trace mineral essential to human health. Boron compounds are also found in low levels in drinking water and soil. Adequate boron is necessary to increase bone density and prevent bone loss, especially among postmenopausal women and others at a high risk for osteoporosis. It may treat or prevent osteoarthritis and rheumatoid arthritis. Some athletes are now taking it to promote better muscle growth, energy metabolism, and hand-eye coordination.