Minerals, essential inorganic substances, are necessary for the body in small amounts. They play a crucial role in various processes, such as bone and teeth formation, fluid balance, nerve conduction, muscle contraction, signaling, and catalysis. It is important to note that certain minerals act as essential enzyme cofactors. Similar to organic vitamins, minerals are considered micronutrients and are required in milligram (mg) or microgram (µg) quantities. The macrominerals are the ones needed in the largest quantities by adults (>100 mg/day), while the microminerals, also known as trace minerals, are required in amounts between 1 and 100 mg/day. Ultratrace minerals are required in amounts less than 1 mg/day. The classification of specific minerals into these categories may vary among sources. The body's mineral concentrations are influenced by their rates of absorption and excretion.

Moving on to the macrominerals, they include calcium (Ca2+), phosphorus ([P] as inorganic phosphate [Pi, or PO43−]), magnesium (Mg2+), sodium (Na+), chloride (Cl−), and potassium (K+). Calcium and phosphorus are often considered together since they are components of hydroxylapatite (Ca5[PO4]3OH), which forms bones and teeth.

Calcium, the most abundant mineral in the body, with approximately 98% found in bones, is involved in various processes such as signaling, muscle contraction, and blood clotting. It binds to different proteins, including calmodulin, phospholipase A2, and protein kinase C, altering their activity. Calbindin, a vitamin D-induced intracellular calcium-binding protein, plays a role in calcium absorption in the intestine. Dairy products, certain green vegetables (like broccoli but not spinach), and fortified orange juice are good dietary sources of calcium. Although dietary deficiency syndromes related to calcium are unknown, the average calcium intake in the United States is insufficient for optimal bone health. Toxicity is only observed with supplements, where the tolerable upper limit for adults is set at 2,500 mg/day. Elevated serum calcium levels (hypercalcemia) can result from excessive production of parathyroid hormone (PTH), causing constipation and kidney stones. On the other hand, low serum calcium levels (hypocalcemia) can occur due to a deficiency of PTH or vitamin D, leading to bone demineralization (resorption). The regulation of serum calcium levels by hormones was previously discussed in the vitamin D section of Chapter 28 and is further reviewed below.

Bone mass increases from infancy through the early reproductive years and then undergoes age-related loss, increasing the risk of fractures in both men and women. This loss is particularly significant in postmenopausal Caucasian women. Studies have indicated that supplementation with calcium and vitamin D can reduce this risk.
Minerals are inorganic substances (elements) required in small amounts by the body. They function in a number of processes including formation of bones and teeth, fluid balance, nerve conduction, muscle contraction, signaling, and catalysis. [Note: Several minerals are essential enzyme cofactors.] Like the organic vitamins (see Chapter 28), minerals are micronutrients required in mg or µg amounts. Those required by adults in the largest amounts (>100 mg/day) are referred to as the macrominerals. Minerals required in amounts between 1 and 100 mg/day are the microminerals (trace minerals). Ultratrace minerals are required in amounts <1 mg/day (Fig. 29.1). [Note: The classification of specific minerals into these categories can vary among sources.] Mineral concentrations in the body are influenced by their rates of absorption and excretion.
II. MACROMINERALS
The macrominerals include calcium (Ca2+), phosphorus ([P] as inorganic phosphate [Pi, or PO43−]), magnesium (Mg2+), sodium (Na+), chloride (Cl−), and potassium (K+). [Note: The free ionic forms are electrolytes.]
A. Calcium and phosphorus
These macrominerals are considered together because they are components of hydroxylapatite (Ca5[PO4]3OH), which makes up bones and teeth.
1. Calcium: Ca2+ is the most abundant mineral in the body, with ~98% being found in bones. The remainder is involved in a number of processes such as signaling, muscle contraction, and blood clotting. Ca2+ binds to a variety of proteins including calmodulin (see p. 133), phospholipase A2 (see p. 213), and protein kinase C (see p. 205) and alters their activity. [Note: Calbindin is a vitamin D–induced intracellular Ca2+-binding protein involved in Ca2+ absorption in the intestine (see p. 392).] Dairy products, many green vegetables (for example, broccoli, but not spinach), and fortified orange juice are good dietary sources. Although dietary deficiency syndromes are unknown, average Ca2+ intake in the United States is insufficient for optimal bone health. Toxicity is seen only with supplements (tolerable upper limit [UL] = 2,500 mg/day for adults). Hypercalcemia (elevated serum Ca2+) can result from overproduction of parathyroid hormone (PTH). This may cause constipation and kidney stones. Hypocalcemia (low serum Ca2+) can result from a deficiency of PTH or vitamin D. It can lead to bone demineralization (resorption). [Note: The hormonal regulation of serum Ca2+ levels was presented in the vitamin D section of Chapter 28 and is reviewed in 3. below.]
Bone mass increases from infancy through the early reproductive years and then shows an age-related loss in both men and women that increases the risk for fracture. This loss is greatest in postmenopausal Caucasian women. Some studies have shown that supplementation with Ca2+ and vitamin D decreases this risk.