Mineral Functions: The Metals and Salts You Need
Calcium, iron, potassium and more. What dietary minerals do inside the body and the foods that supply them.
What Are Dietary Minerals?
Dietary minerals are naturally occurring inorganic elements — they cannot be made from carbon-containing molecules the way vitamins can. They enter the food chain through soil and water, are taken up by plants, and consumed by animals. When you eat food, you absorb these minerals and use them for an enormous range of structural and regulatory purposes.
The body needs more than 20 different minerals, which are broadly divided into macrominerals (required in amounts of 100 mg or more per day) and trace minerals (required in much smaller amounts, sometimes just micrograms). Both groups are equally essential — the "trace" label refers to quantity needed, not importance.
To understand how minerals work alongside other essential nutrients, see our companion vitamins explained post.
Calcium: The Bone and Signal Mineral
Calcium is the most abundant mineral in the body, with about 99% stored in bones and teeth. It gives the skeleton its hardness and serves as a calcium reservoir the body draws on when blood calcium levels fall. The remaining 1% plays crucial roles in muscle contraction (including the heartbeat), nerve signal transmission, blood clotting, and enzyme function.
When dietary calcium is insufficient, the body leaches calcium from bones to maintain blood levels — fine in the short term, but damaging to bone density over years. Adequate calcium intake throughout life, especially during childhood, adolescence, and early adulthood when bones are still growing, is important for reaching maximum bone density. See our bones guide for more on how bones are built and maintained.
Rich sources include dairy products, fortified plant milks, tofu set with calcium, tinned fish eaten with bones (like sardines), and leafy greens such as kale and pak choi. Vitamin D is essential for calcium absorption — without adequate D, the body cannot properly use the calcium from food.
Iron: Oxygen Delivery
Iron is central to one of the body's most vital tasks: carrying oxygen. It is a key component of haemoglobin, the protein in red blood cells that binds to oxygen in the lungs and releases it to tissues throughout the body. Iron is also found in myoglobin (which stores oxygen in muscle cells) and in many enzymes involved in energy production.
Iron deficiency is the most common nutritional deficiency worldwide, and it leads to iron-deficiency anaemia — characterised by fatigue, pallor, breathlessness, and reduced ability to concentrate. Women of reproductive age have higher iron needs because of menstrual losses.
Key Minerals at a Glance
| Mineral | Main Role(s) | Good Food Sources |
|---|---|---|
| Calcium | Bone/teeth structure; muscle contraction; blood clotting | Dairy, fortified plant milks, leafy greens, tinned sardines |
| Iron | Oxygen transport (haemoglobin); energy metabolism | Red meat, lentils, spinach, fortified cereals |
| Potassium | Fluid balance; nerve signals; heart rhythm | Bananas, potatoes, avocado, beans, dairy |
| Sodium | Fluid balance; nerve and muscle function | Salt, processed foods, bread, cheese |
| Magnesium | Protein synthesis; muscle and nerve function; blood glucose | Nuts, seeds, wholegrains, leafy greens, dark chocolate |
| Phosphorus | Bone/teeth structure; energy transfer (ATP) | Meat, dairy, fish, nuts, wholegrains |
| Zinc | Immune function; wound healing; taste and smell | Meat, shellfish (especially oysters), nuts, legumes |
| Iodine | Thyroid hormone production; metabolism regulation | Seafood, dairy, iodised salt, seaweed |
| Selenium | Antioxidant function; thyroid metabolism | Brazil nuts, fish, meat, eggs |
Potassium and Sodium: The Fluid Balance Pair
Potassium and sodium work together to regulate fluid balance — controlling how much water is inside and outside cells — and to generate the electrical signals that allow nerves to fire and muscles to contract. The sodium-potassium pump in cell membranes uses energy to maintain a sodium gradient (higher outside cells) and a potassium gradient (higher inside cells) that is fundamental to how electrically excitable cells work.
Most people in modern diets consume more sodium and less potassium than is ideal. High sodium intake is associated with raised blood pressure in people who are salt-sensitive — though the relationship is more nuanced than sometimes portrayed. Potassium appears to partly counteract some of sodium's effects on blood pressure. Fruits, vegetables, and legumes are the richest sources of potassium.
For a practical look at how fluid balance works in the body, our hydration facts post covers sodium's role alongside water intake.
Magnesium: The Quiet Workhorse
Magnesium is involved in over 300 enzyme reactions in the body — more than almost any other mineral. It plays roles in protein synthesis, DNA repair, nerve and muscle function, blood glucose regulation, and energy production. Bones and teeth contain about 60% of the body's magnesium; the rest is in soft tissues and blood.
Magnesium deficiency is not rare, as modern diets are often low in the wholegrains, nuts, seeds, and leafy greens that supply it. Chronic low-level deficiency may contribute to muscle cramps and fatigue, though symptoms are non-specific and many things cause these complaints. Nuts (especially almonds and cashews), pumpkin seeds, spinach, and dark chocolate are particularly rich sources.
Zinc and Iodine: Specific but Essential
Zinc is required for hundreds of enzymes, including those involved in immune function, wound healing, protein synthesis, and cell division. It is also essential for the senses of taste and smell. Deficiency causes immune impairment, slow wound healing, and in growing children, stunted development. Zinc from animal sources is more bioavailable than from plants, partly because plant foods contain phytates that can bind zinc and reduce absorption.
Iodine is needed to produce thyroid hormones, which regulate the body's metabolic rate and are essential for brain development in foetuses and young children. Deficiency causes goitre (swelling of the thyroid gland) and, during pregnancy, can impair foetal brain development. Seafood and dairy are the richest natural sources; iodised salt has helped address deficiency in many regions where soil iodine is low.
Other Trace Minerals
Beyond those already covered, several other trace minerals play specific essential roles:
- Selenium: An antioxidant that protects cells from oxidative damage, and important for thyroid hormone metabolism. A single Brazil nut often contains more than a day's requirement.
- Copper: Needed for iron metabolism, nerve function, and building connective tissue. Found in shellfish, nuts, seeds, and dark chocolate.
- Manganese: Involved in bone formation, carbohydrate metabolism, and antioxidant defence. Wholegrains, tea, and leafy vegetables are good sources.
- Chromium: Helps insulin work effectively in regulating blood glucose. Found in meats, wholegrains, and broccoli.
- Fluoride: Strengthens tooth enamel and bones. The fluoridation of drinking water in many regions is one of the most cost-effective public health interventions for reducing tooth decay.
Getting Enough Minerals Through Diet
A varied diet that includes different food groups is the most reliable way to cover mineral needs. No single food provides everything. A practical approach includes:
- Plenty of vegetables and fruits (potassium, magnesium, some calcium)
- Wholegrains rather than refined grains (magnesium, zinc, manganese, selenium)
- Legumes, nuts, and seeds (iron, zinc, magnesium, calcium)
- Dairy or fortified plant alternatives (calcium, iodine)
- Lean meat, fish, or eggs (iron, zinc, selenium, iodine)
For those with specific dietary restrictions or health conditions, a registered dietitian can assess whether targeted supplementation is appropriate. You can also explore nutritional information with our nutrition planner or read the broader vitamins and minerals guide for a complete overview of micronutrition. Remember that mineral supplements — like vitamins — can cause harm in excess: more is not always better, and professional guidance takes precedence over general information for specific health concerns.