Minerals are inorganic elements required for diverse physiological functions — structural (bone, teeth), electrochemical (nerve transmission, muscle contraction), catalytic (enzyme cofactors), and regulatory (fluid balance, acid-base balance). They are classified as macrominerals (required >100 mg/day) or trace minerals (required <100 mg/day).
Macrominerals
Calcium
Functions. 99% of body calcium is in bones and teeth as hydroxyapatite. The 1% in blood and cells is tightly regulated and essential for blood clotting, muscle contraction, nerve transmission, hormone secretion, and cell signaling. Calcium balance is regulated by parathyroid hormone (PTH), vitamin D, and calcitonin.
Sources. Dairy products (milk, yogurt, cheese) are the richest sources. Fortified plant milks, calcium-set tofu, sardines with bones, canned salmon, kale, broccoli, and fortified orange juice. Bioavailability is highest from dairy.
RDA. 1000 mg/day for adults 19–50 years; 1200 mg/day for women over 50 and men over 70. Most adults do not meet recommended intakes.
Deficiency. Osteopenia, osteoporosis, increased fracture risk. Severe deficiency causes hypocalcemia (tetany, paresthesias, Chvostek and Trousseau signs, prolonged QT interval). Chronic low calcium intake is associated with hypertension, preeclampsia, and colon cancer.
Toxicity. Hypercalcemia (rare from diet alone). Upper limit: 2500 mg/day. Calcium supplements (especially >500 mg per dose) may increase kidney stone risk.
Phosphorus
Functions. Component of hydroxyapatite (bone), ATP (energy currency), DNA and RNA backbone, phospholipids (cell membranes), and intracellular signaling.
Sources. Widely distributed in protein-rich foods: meat, poultry, fish, dairy, eggs, legumes, nuts, whole grains. Phosphorus additives in processed foods (phosphoric acid in colas, phosphate salts) are highly absorbable.
RDA. 700 mg/day for adults.
Deficiency. Hypophosphatemia (rare, seen in refeeding syndrome, chronic antacid use, alcoholism): muscle weakness, bone pain, respiratory failure, hemolysis.
Magnesium
Functions. Cofactor for over 300 enzymes, including ATP-dependent reactions. Stabilizes nucleic acids and cell membranes. Required for muscle and nerve function, blood glucose control, blood pressure regulation, and protein synthesis.
Sources. Green leafy vegetables (chlorophyll contains magnesium), nuts, seeds, legumes, whole grains, and some fish. Processing reduces magnesium content (white flour loses 80% of magnesium).
RDA. 310–420 mg/day for adults. Many adults consume less than the RDA.
Deficiency. Hypomagnesemia: muscle cramps, weakness, fatigue, tremor, tetany, seizures, cardiac arrhythmias (prolonged QT). Associated with type 2 diabetes, hypertension, cardiovascular disease, and migraine.
Sodium
Functions. Primary extracellular cation. Regulates fluid balance, acid-base balance, nerve transmission, and muscle contraction.
Sources. Table salt (40% sodium, 60% chloride). Processed foods account for 70% of sodium intake — bread, processed meats, pizza, soups, sandwiches, and savory snacks.
Adequate intake. 1500 mg/day for adults. Upper limit: 2300 mg/day (about 1 teaspoon of salt). Average US consumption: 3400 mg/day.
Excess effects. Hypertension, cardiovascular disease, stroke, and kidney disease. Sodium reduction lowers blood pressure in a dose-dependent manner, especially in those with hypertension, older age, and African ancestry.
Potassium
Functions. Primary intracellular cation. Regulates fluid balance, nerve transmission, muscle contraction, and blood pressure. Works in opposition to sodium.
Sources. Fruits (bananas, oranges, cantaloupe, apricots), vegetables (potatoes, sweet potatoes, spinach, tomatoes, avocado), legumes, dairy, and fish.
Adequate intake. 3400 mg/day for men; 2600 mg/day for women. Most adults consume well below these levels.
Deficiency. Hypokalemia: muscle weakness, fatigue, cardiac arrhythmias, glucose intolerance. Causes: diuretic use, diarrhea, poor intake.
Chloride
Functions. Primary extracellular anion. Maintains fluid balance, gastric acid (HCl) production, and acid-base balance. Usually consumed with sodium as table salt. Deficiency is rare.
Sulfur
Functions. Component of methionine and cysteine (sulfur amino acids), biotin, thiamine, and glutathione (antioxidant). Obtained from dietary protein.
Trace Minerals
Iron
Functions. Component of hemoglobin and myoglobin (oxygen transport and storage) and cytochromes (electron transport chain). Heme iron (from animal sources) is 15–35% bioavailable; non-heme iron (from plants) is 2–20% bioavailable (enhanced by vitamin C, meat, and reduced by phytates, tannins).
RDA. 8 mg/day for men and postmenopausal women; 18 mg/day for premenopausal women; 27 mg/day during pregnancy.
Deficiency. Iron deficiency anemia: fatigue, weakness, pallor, dyspnea, palpitations, pica (pagophagia — ice craving), restless legs, impaired cognitive performance. The most common micronutrient deficiency globally, affecting 30% of the world’s population.
Toxicity. Iron overload (hemochromatosis): hereditary condition causing iron accumulation and organ damage (liver, heart, pancreas, joints). Acute iron poisoning is a medical emergency in children.
Zinc
Functions. Cofactor for over 100 enzymes, involved in gene expression, immune function, wound healing, growth, and taste perception.
Sources. Oysters (richest source), red meat, poultry, beans, nuts, whole grains, fortified cereals.
RDA. 8–11 mg/day for adults.
Deficiency. Growth retardation, impaired immune function (increased infection risk), diarrhea, alopecia, dermatitis, delayed wound healing, hypogonadism, and loss of taste (hypogeusia).
Iodine
Functions. Component of thyroid hormones (T3, T4), which regulate metabolism, growth, and development. Iodine deficiency during pregnancy causes cretinism (irreversible intellectual disability).
Sources. Iodized salt (US salt is fortified with iodine at 45 mcg/g), seafood, dairy, eggs. Seaweed is very rich but variable in content.
RDA. 150 mcg/day for adults; 220–290 mcg during pregnancy and lactation.
Deficiency. Goiter (enlarged thyroid), hypothyroidism, intellectual impairment, and cretinism. Iodine deficiency is the leading preventable cause of intellectual disability worldwide.
Selenium
Functions. Component of selenoproteins, including glutathione peroxidase (antioxidant) and thyroid deiodinases (thyroid hormone metabolism). Supports immune function and reproduction.
Sources. Brazil nuts (extremely rich — one nut provides >100 mcg), seafood, organ meats, poultry, eggs, and grains (depending on soil selenium content).
RDA. 55 mcg/day for adults.
Deficiency. Keshan disease (cardiomyopathy), Kashin-Beck disease (osteoarthritis), impaired immune function.
Toxicity. Selenosis: garlic breath, brittle hair and nails, gastrointestinal distress, and neurological symptoms.
Copper
Functions. Cofactor for enzymes involved in iron metabolism, antioxidant defense (superoxide dismutase), collagen and elastin cross-linking, and neurotransmitter synthesis.
Sources. Liver, shellfish (oysters), nuts, seeds, whole grains, chocolate, legumes.
RDA. 900 mcg/day for adults.
Deficiency. Rare — anemia, neutropenia, osteoporosis, neurological symptoms. Seen in Menkes disease (copper transport disorder).
Other Trace Minerals
Manganese. Cofactor for enzymes in bone formation, metabolism, and antioxidant defense. Sources: whole grains, legumes, nuts, tea.
Chromium. Enhances insulin action. Sources: broccoli, whole grains, meat. Deficiency is rare. Chromium supplements for blood glucose control have inconsistent evidence.
Molybdenum. Cofactor for enzymes in sulfur amino acid and purine metabolism. Deficiency is extremely rare.
Fluoride. Promotes remineralization of tooth enamel and prevents dental caries. Sources: fluoridated water, tea, and fish. Adequate intake: 3–4 mg/day. Excess causes dental fluorosis (mottling of teeth).
Summary
Essential minerals are categorized as macrominerals (calcium, phosphorus, magnesium, sodium, potassium, chloride, sulfur) and trace minerals (iron, zinc, copper, selenium, iodine, manganese, chromium, molybdenum, fluoride). Each has specific functions, deficiency syndromes, and food sources. Calcium, iron, and iodine deficiencies are the most prevalent. Fortification and supplementation address the most common deficiencies. A balanced diet with adequate variety provides sufficient minerals for most healthy individuals.