Dietary minerals are essential inorganic elements that serve as enzyme cofactors, structural components of tissues, and electrolytes that maintain osmotic balance and membrane potentials. They are classified as macrominerals required in amounts greater than 100 milligrams daily, and trace minerals required in smaller amounts.
Iron
Iron is essential for oxygen transport in hemoglobin and myoglobin and as a cofactor for cytochromes, catalase, and other enzymes. Iron exists in ferrous and ferric forms, and its redox cycling is central to its function. Heme iron from animal sources is more bioavailable than non-heme iron from plants. Iron absorption is regulated by hepcidin, a peptide hormone that controls ferroportin-mediated iron export from enterocytes.
Iron deficiency causes microcytic hypochromic anemia with fatigue, pallor, and pica. Iron overload causes hemochromatosis with liver cirrhosis, diabetes, and cardiomyopathy. Hereditary hemochromatosis results from HFE mutations causing unregulated iron absorption.
Calcium
Calcium is the most abundant mineral in the body, with 99% stored in bone as hydroxyapatite. It is essential for bone structure, muscle contraction, nerve transmission, blood clotting, and intracellular signaling. Serum calcium is tightly regulated by parathyroid hormone, vitamin D, and calcitonin. PTH increases calcium by promoting bone resorption, renal reabsorption, and vitamin D activation. Hypocalcemia causes tetany and paresthesias. Hypercalcemia causes kidney stones, abdominal pain, and confusion.
Zinc
Zinc is a cofactor for over 300 enzymes, including alcohol dehydrogenase, alkaline phosphatase, and matrix metalloproteinases. It also stabilizes the zinc finger domains of many transcription factors. Zinc is found in meat, shellfish, and legumes. Deficiency causes growth retardation, hypogonadism, immune dysfunction, and delayed wound healing. Acrodermatitis enteropathica is a genetic zinc malabsorption disorder.
Magnesium
Magnesium is a cofactor for over 600 enzymes, including all ATP-requiring enzymes. It stabilizes ATP, nucleic acids, and membranes. Magnesium is found in green leafy vegetables, nuts, and whole grains. Deficiency causes muscle cramps, weakness, arrhythmias, and hypocalcemia resistant to correction. Hypermagnesemia causes hypotension and respiratory depression.
Copper
Copper is a cofactor for cytochrome c oxidase, superoxide dismutase, lysyl oxidase, and dopamine beta-hydroxylase. It is absorbed in the small intestine and transported by ceruloplasmin. Wilson disease causes copper accumulation in liver and brain due to ATP7B mutations, presenting with liver disease and neurological symptoms. Menkes disease is an X-linked copper deficiency disorder with kinky hair, neurological degeneration, and connective tissue abnormalities.
Selenium
Selenium is incorporated into selenoproteins as selenocysteine, the 21st amino acid. Glutathione peroxidases and thioredoxin reductases are important selenoenzymes involved in antioxidant defense and redox regulation. Selenium is found in Brazil nuts, seafood, and organ meats. Deficiency contributes to Keshan disease, a cardiomyopathy affecting selenium-poor regions of China, and Kashin-Beck disease, an osteoarthropathy.
Iodine
Iodine is essential for thyroid hormone synthesis. The sodium-iodide symporter concentrates iodide in the thyroid, where it is incorporated into thyroglobulin. Iodine deficiency causes goiter and hypothyroidism, and is the leading preventable cause of intellectual disability worldwide. Iodized salt has dramatically reduced deficiency prevalence. Excess iodine can also cause thyroid dysfunction.
Other Trace Minerals
Manganese is a cofactor for arginase, superoxide dismutase, and pyruvate carboxylase. Molybdenum is a cofactor for sulfite oxidase and xanthine oxidase. Chromium potentiates insulin action, though its essentiality in humans is debated. Fluoride strengthens tooth enamel and prevents dental caries. Cobalt is a component of vitamin B12. Silicon and boron are considered possibly essential but their biochemical roles are less well defined.
