Minerals in nutrition are inorganic elements your body needs to function but cannot produce on its own. You get them from food, water, and sometimes supplements. They play roles in everything from building bones to transmitting nerve signals, and they split into two categories based on how much your body requires: macrominerals and trace minerals.
Macrominerals vs. Trace Minerals
The distinction is straightforward. Macrominerals are the ones your body needs in relatively large amounts, typically hundreds or thousands of milligrams per day. There are seven: calcium, phosphorus, magnesium, sodium, potassium, chloride, and sulfur. Trace minerals are needed in much smaller quantities, sometimes just micrograms. The essential trace minerals include iron, zinc, iodine, selenium, copper, manganese, fluoride, and cobalt.
“Large” and “small” are relative here. An adult needs about 1,000 mg of calcium per day but only 300 micrograms of selenium, a difference of more than 3,000-fold. Both are equally essential. Running low on a trace mineral can be just as damaging as running low on a macromineral.
What Macrominerals Do in Your Body
Calcium and phosphorus are the structural minerals. Together they form hydroxyapatite, the crystal compound that makes bones and teeth hard. The process works like this: calcium and phosphate ions accumulate in tiny pockets within collagen fibers, where they precipitate into crystals that spread along the fiber surface. About 99% of the calcium in your body is locked in your skeleton, but the remaining 1% circulates in your blood, where it’s critical for muscle contraction, blood clotting, and cell signaling. Most adults need 1,000 mg of calcium daily, rising to 1,200 mg for women over 50 and men over 70.
Magnesium is a behind-the-scenes workhorse. It serves as a cofactor in over 300 enzymatic reactions inside your cells, and every single reaction that involves ATP (your body’s energy currency) has an absolute requirement for magnesium. That means energy production, protein synthesis, and DNA repair all depend on it. Adult men need about 400 to 420 mg per day, and women need 310 to 320 mg.
Sodium and potassium work as a pair. They create the electrical charge difference across every cell membrane in your body, which is what makes nerve signaling possible. When a nerve fires, sodium rushes into the cell to generate an electrical spike called an action potential. Immediately after, a pump on the cell membrane trades three sodium ions back out for two potassium ions coming in, resetting the cell so it’s ready to fire again. This pump runs constantly in your brain, muscles, and heart. Adults need about 1,500 mg of sodium and 2,600 to 3,400 mg of potassium per day. Most people get far too much sodium and not nearly enough potassium.
What Trace Minerals Do in Your Body
Iron is central to oxygen transport. It sits at the core of hemoglobin, the protein in red blood cells that picks up oxygen in your lungs and delivers it to tissues throughout your body. Without enough iron, your cells are starved for oxygen, which is why iron deficiency causes fatigue, weakness, and poor concentration before it progresses to full anemia.
Zinc supports immune function and wound healing. It also plays a role in thyroid hormone regulation, and supplementing zinc has been shown to improve thyroid function by influencing the levels of key thyroid hormones. Your body has no dedicated zinc storage system, so you need a consistent daily intake from food.
Iodine is the raw material for thyroid hormones, which control your metabolic rate, body temperature, and growth. Selenium protects the thyroid gland from oxidative damage and helps convert thyroid hormones into their active form. These two trace minerals work together so closely that a deficiency in one can worsen the effects of a deficiency in the other.
How Common Are Mineral Deficiencies?
Far more common than most people realize. A 2024 modelling analysis published in The Lancet Global Health estimated that more than 5 billion people worldwide, roughly 68% of the global population, do not consume enough iodine. Iron inadequacy is nearly as widespread, affecting about 4 billion people, or 65% of the world’s population. These aren’t just problems in low-income countries. Even in places with diverse food supplies, soil depletion, food processing, and dietary patterns leave large gaps in mineral intake.
Iron deficiency is especially common in women of reproductive age due to menstrual blood loss, and in young children during periods of rapid growth. Iodine deficiency remains a concern in regions where the soil is naturally low in iodine and iodized salt isn’t widely used.
Why Eating Minerals Isn’t the Same as Absorbing Them
The amount of a mineral listed on a food label doesn’t tell you how much your body will actually take up. Bioavailability, the proportion that gets absorbed and used, varies dramatically depending on what else you eat at the same meal.
Several naturally occurring compounds in food interfere with mineral absorption:
- Phytates in whole grains, seeds, legumes, and some nuts decrease the absorption of iron, zinc, magnesium, and calcium.
- Oxalates in spinach, Swiss chard, beets, and tea bind to calcium and prevent it from being absorbed. Spinach is technically rich in calcium, but your body can only access a small fraction of it.
- Tannins in tea and coffee reduce iron absorption, which is why drinking tea with a meal can blunt the iron you get from that food.
- Lectins in beans, peanuts, and whole grains can interfere with the absorption of calcium, iron, phosphorus, and zinc.
- Glucosinolates in cruciferous vegetables like broccoli, kale, and cabbage can block iodine absorption and, in large enough amounts, interfere with thyroid function.
The practical fix is simpler than it sounds. Soaking, sprouting, boiling, and fermenting foods all break down these compounds. Boiling vegetables for about 12 minutes can reduce their oxalate content by 30 to 87%, with leafy greens like spinach losing up to 85% of their oxalates. Timing matters too: drinking tea or coffee between meals instead of with meals reduces its impact on iron absorption. Eating a variety of foods throughout the day rather than loading up on a single high-fiber or high-oxalate meal at once also helps.
When You Get Too Much
Minerals can be toxic in excess, and the margin between a healthy dose and a harmful one is surprisingly narrow for some trace minerals. This is rarely a concern from food alone but becomes relevant with supplements.
Excess magnesium from supplements (not from food) causes diarrhea at relatively low doses. The upper limit for supplemental magnesium is set at 250 mg per day from sources like magnesium citrate or magnesium oxide. That diarrhea is reversible within a day or two, but at extremely high doses above 2,500 mg, magnesium toxicity can cause dangerously low blood pressure and muscle weakness.
Selenium toxicity, called selenosis, produces distinctive symptoms: brittle hair that loses its pigment, thickened and spotted nails, red swollen skin with blisters, and eventually neurological problems including numbness, pain, and motor disturbances. The upper limit for selenium is 300 micrograms per day for adults. Brazil nuts are the richest food source, with a single nut containing roughly 70 to 90 micrograms, which means just a handful can push you past the safe limit.
Too much iodine causes a condition called iodism, which resembles a chronic cold: runny nose, swollen salivary glands, metallic taste, skin breakouts, and irritated eyes. The upper limit for adults is 600 micrograms per day. Seaweed and kelp supplements are the most common sources of accidental iodine excess.
Best Food Sources by Mineral
You don’t need a complicated diet to cover your mineral needs. A few strategic food choices go a long way.
For calcium, dairy products remain the most bioavailable source. Fortified plant milks, canned sardines and salmon (with bones), and leafy greens like bok choy and kale also contribute meaningful amounts. Spinach contains calcium, but its high oxalate content blocks most of it.
For magnesium, think seeds, nuts, and dark leafy greens. Pumpkin seeds, almonds, and cooked spinach (where the oxalates don’t interfere with magnesium as much as they do with calcium) are all reliable sources. Whole grains and dark chocolate also contribute.
For potassium, bananas get all the attention, but potatoes, beans, lentils, dried apricots, and avocados contain more potassium per serving. Most fruits and vegetables contribute some amount.
For iron, the type matters. Heme iron from animal sources like red meat, poultry, and shellfish is absorbed at roughly two to three times the rate of non-heme iron from plant sources like lentils, beans, and fortified cereals. Pairing plant-based iron sources with vitamin C (citrus, bell peppers, tomatoes) significantly boosts absorption.
For zinc, oysters are the single richest source by far. Red meat, poultry, beans, nuts, and fortified cereals also provide zinc, though plant sources again face the bioavailability challenge from phytates.
For iodine, iodized salt is the simplest and most reliable source. Dairy products, seafood, and seaweed also contain iodine, though the amount in seaweed varies enormously by type and can easily overshoot the safe range.