Minerals — Overview (Magnesium, Zinc, and the Remaining Trace Minerals)

Minerals are inorganic elements the body cannot make and must obtain from food. They split into major (macro) minerals — needed in amounts above ~100 mg/day (calcium, phosphorus, magnesium, potassium, sodium, chloride, sulfur) — and trace (micro) minerals — needed in milligram-to-microgram amounts (iron, zinc, copper, selenium, iodine, manganese, chromium). Calcium, iron, and sodium/potassium each have their own dedicated modules (see Connections); this entry covers the rest.

• Magnesium: a cofactor in 300+ enzymatic reactions including ATP/energy metabolism, muscle and nerve function, and protein synthesis. RDA 400 mg/day (men 19–30), 420 mg (men 31+); 310 mg (women 19–30), 320 mg (women 31+). UL 350 mg/day applies only to magnesium from supplements or medicines, not food. Found in nuts, seeds, legumes, whole grains, and leafy greens. Supplements make most sense when intake is genuinely low.
• Zinc: supports immune function, protein synthesis, wound healing, and testosterone metabolism. RDA 11 mg/day (men), 8 mg/day (women); UL 40 mg/day. Found in meat, shellfish, legumes, and seeds. Vegetarians absorb less (phytates inhibit absorption) and are an at-risk group.
• Phosphorus: structural component of bone/teeth and cell membranes, and central to ATP energy metabolism. RDA 700 mg/day (both sexes); UL 4,000 mg/day (ages 19–70). Found in dairy, eggs, meat/poultry/fish, legumes, nuts, and whole grains — plus "hidden" phosphorus from phosphate additives in processed foods. Dietary deficiency is rare; excess mainly comes from additives, not whole food.
• Chloride: partners with sodium and potassium to regulate fluid balance and cell osmotic pressure, and forms stomach acid (HCl) for digestion. AI 2.3 g/day (ages 9–50, both sexes), 2.0 g (51–70), 1.8 g (over 70); UL 3.6 g/day (ages 14+). Intake tracks with sodium, so excess concerns follow the same salt-reduction guidance as sodium. Found in table/sea salt and the same high-sodium foods (deli meats, cheese, condiments). True deficiency is rare outside severe fluid loss (vomiting, diarrhea, heavy sweat).
• Copper: a cofactor for enzymes involved in iron metabolism/red blood cell formation, collagen synthesis, and antioxidant defense. RDA 900 mcg/day (both sexes); UL 10,000 mcg/day. Found in shellfish (especially oysters), organ meats, nuts/seeds (cashews, sesame, sunflower), whole grains, and chocolate. Deficiency is uncommon but can be triggered by excess zinc supplementation, which competes with copper for absorption.
• Selenium: a cofactor for antioxidant enzymes and thyroid hormone metabolism. RDA 55 mcg/day (both sexes); UL 400 mcg/day. Found in Brazil nuts (extremely concentrated; even 1–2 nuts can exceed the RDA), seafood, meat, and poultry. Selenium toxicity from over-relying on Brazil nuts or supplements is a genuine risk; the UL is 400 mcg/day.
• Iodine: essential for synthesizing thyroid hormones, which regulate metabolic rate. RDA 150 mcg/day (both sexes); UL 1,100 mcg/day. Found in iodized salt, dairy, eggs, seaweed, and saltwater fish. Real deficiency risk exists for people who avoid iodized salt and dairy — e.g. those using only non-iodized sea/kosher salt, or following restrictive plant-heavy diets without seaweed.
• Manganese: a cofactor for enzymes involved in bone formation and amino acid/cholesterol/carbohydrate metabolism. AI 2.3 mg/day (men), 1.8 mg/day (women); UL 11 mg/day. Found in whole grains, nuts, legumes, tea, and leafy vegetables. Both dietary deficiency and diet-driven toxicity are essentially unheard of — not a practical concern for most people.
• Chromium: may enhance insulin action, potentially supporting carbohydrate/lipid/protein metabolism. AI 35 mcg/day (men), 25 mcg/day (women), ages 19–50 (30 and 20 mcg after 50); no UL established. Found in meat, whole grains, broccoli, and grape/orange juice. Chromium picolinate is widely marketed for blood-sugar control and weight loss, but clinical evidence for a meaningful benefit in people without a documented deficiency is weak and inconsistent — treat supplement marketing claims skeptically.

For most people a varied whole-food diet covers mineral needs. Mineral supplements are warranted for documented deficiencies or defined at-risk groups, and megadoses of trace minerals can be toxic (e.g., zinc excess impairs copper absorption; selenium megadosing on Brazil nuts causes real toxicity symptoms).

• Inorganic micronutrients; major minerals (>100 mg/day) vs. trace minerals (mg-to-mcg/day).
• Magnesium: 300+ enzyme cofactor; RDA 400–420 mg (M) / 310–320 mg (W); UL 350 mg from supplements only.
• Zinc: immunity/protein synthesis/healing; RDA 11 mg (M) / 8 mg (W); UL 40 mg; vegetarians absorb less.
• Phosphorus: bone + ATP metabolism; RDA 700 mg (both); UL 4,000 mg; deficiency rare, additives are the real excess source.
• Chloride: fluid balance + stomach acid; AI 2.3 g/day (9–50), lower after 50; UL 3.6 g/day; tracks with sodium intake.
• Copper: iron metabolism/collagen/antioxidant enzymes; RDA 900 mcg; UL 10,000 mcg; antagonized by excess zinc.
• Selenium: antioxidant + thyroid enzymes; RDA 55 mcg; UL 400 mcg; 1–2 Brazil nuts can exceed the RDA; habitual large amounts risk toxicity.
• Iodine: thyroid hormone synthesis; RDA 150 mcg; UL 1,100 mcg; real deficiency risk if avoiding iodized salt/dairy.
• Manganese: bone + metabolism cofactor; AI 2.3 mg (M) / 1.8 mg (W); deficiency/toxicity both rare.
• Chromium: possible insulin-action support; AI 35 mcg (M) / 25 mcg (W) ages 19–50; no UL; supplement weight-loss claims are weakly supported.
• Varied diet usually suffices; trace-mineral megadoses can be toxic.