Solid mineral crystals in your bones impart them with the strength and rigidity to support your body and withstand powerful physical stresses. Calcium and phosphorus are the most abundant minerals in your bones, together forming calcium phosphate crystals. Your bones contain roughly 99 percent of the calcium and 85 percent of the phosphorus in your body. Other minerals stored in your bones include magnesium and fluoride.
Roles of Bone Minerals
The minerals in your bones serve two primary functions. As components of mixed crystals, minerals transform spongy bone matrix into a rigid structure. The level of mineralization in your bones affects their strength. Reduced bone mineralization, or osteomalacia, weakens your bones and increases your risk of fractures.
Your bones also function as a mineral storage depot, releasing dissolved calcium, phosphorus and magnesium into your bloodstream if needed. A persistently low blood calcium level, for example, leads to breakdown of mineral crystals in your bones to correct the deficiency. Although this mechanism avoids potential muscle, heart and nerve malfunctions due to insufficient dissolved calcium, your bone health suffers if you do not consume enough calcium to support both your bones and other body tissues.
Hormonal Mineral Regulation
Hormones regulate the balance between solid mineral crystals in your bones and dissolved minerals in your blood and body tissues. Your parathyroid glands produce parathyroid hormone, or PTH, which stimulates calcium release from your bones and increases your blood level. Specialized cells in your thyroid gland produce the hormone calcitonin, which counteracts PTH by suppressing bone breakdown and mineral release. Both PTH and calcitonin also act on your kidneys to influence your blood calcium level. PTH promotes calcium conservation by limiting urinary loss of the mineral. Conversely, calcitonin promotes urinary excretion of calcium. Vitamin D, which is technically a steroid hormone, affects bone mineralization by enhancing intestinal absorption of calcium and phosphorus, and supporting the activity of PTH.
Although the quantity of magnesium in your bones is significantly less than that of calcium and phosphorus, magnesium remains an important contributor to bone strength. Approximately 60 percent of the magnesium in your body resides in your bones, enhancing their strength and stability. In addition to promoting bone health, magnesium supports muscle activity and functions as an essential cofactor in energy-producing metabolic processes.
Your bones and teeth harbor nearly all of the fluoride in your body. Although normally present in minute quantities, fluoride supports your bone strength by forming crystals in open spaces between the more numerous calcium phosphate crystals. Extremely high levels of fluoride intake — markedly higher than the amounts consumed from a fluoridated water supply — can adversely affect your bones, causing a rare condition known as skeletal fluorosis. The bones increase in size with fluorosis, but exhibit decreased strength due to the displacement of calcium by the fluoride.