LeClaire Institute

Module 2 · Major Minerals

The third micronutrient lesson covers the seven major minerals: sodium, chloride, potassium, calcium, phosphorus, magnesium and sulfur, which you need in amounts over 100 mg a day. It starts with how atoms become ions, then shows each mineral as an ion or simple compound in ball-and-stick form, with what it does in your body, what happens with too little or too much, and where to find it in whole foods. The figure is on the left and the lesson script on the right; the quiz is at the end.

Previous lesson: Module 2 · Water-Soluble Vitamins

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Figure 1

The Major Mineral Family Tree

Seven minerals needed in amounts over 100 mg a day.

Major Mineralsover 100 mg a day, carried as ions · Fig. 2Electrolytescharged ions in body fluids · Figs. 3–4Bone mineralsalso in every cell · Figs. 5–6SulfurFig. 7SodiumNa⁺ · Fig. 3ChlorideCl⁻ · Fig. 3PotassiumK⁺ · Fig. 4CalciumCa²⁺ · Fig. 5Phosphorusphosphate · Fig. 6MagnesiumMg²⁺ · Fig. 6In proteinamino acids · Fig. 7
What makes a mineral “major”
Amount, not importanceMajor minerals are those you need in amounts over about 100 mg a day; trace minerals, such as iron and zinc, are needed in smaller amounts but are just as essential.
Elements, not moleculesA mineral is a single element. It can’t be made or destroyed by the body, or by cooking, though some can be lost into cooking water.
Carried as ionsIn food and in your body, minerals are almost always charged atoms (ions) or parts of simple compounds, not neutral atoms (Figure 2).
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Figure 2

From Atoms to Ions

How minerals get their charge, and the salt crystal.

Giving and taking electrons

Atoms become ions

Sodium ionNa → Na⁺: gives away one electron

Chloride ionCl → Cl⁻: takes one electron

An atom that loses an electron has one more proton than electrons: a positive ion. One that gains an electron becomes a negative ion. Opposite charges attract, and that attraction, an ionic bond, holds salt together. Chloride is drawn bigger than sodium because it is: the extra electron and fewer protons per electron let it spread out.

Table salt: a sodium chloride crystal, NaCl

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  1. 1Every sodium ion is surrounded by chloride ions…
  2. 2…and every chloride by sodium ions. The sticks show neighbors, not shared electrons. The real crystal continues in three dimensions.

The ions of the major minerals, at the same scale

MagnesiumMg²⁺

CalciumCa²⁺

PotassiumK⁺

Magnesium and calcium give away two electrons each (2+); sodium and potassium one (1+). Potassium is bigger than sodium, and that difference in size is how cells tell them apart (Figure 4).

The seven major minerals
MineralMain form in the bodyCharge
Sodiumsodium ion, Na⁺+1
Potassiumpotassium ion, K⁺+1
Calciumcalcium ion, Ca²⁺+2
Magnesiummagnesium ion, Mg²⁺+2
Chloridechloride ion, Cl⁻−1
Phosphorusphosphate, PO₄³⁻ and HPO₄²⁻−3, −2
Sulfurin amino acids; sulfate, SO₄²⁻−2 as sulfate

sodium chlorine potassium calcium magnesium · ions drawn to the same scale (relative ionic size) · tap one to enlarge it

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Figure 3

Sodium and Chloride

Salt in water, fluid balance and stomach acid.

Sodium and chloride

Salt in water: ions surrounded by water

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  1. 1A sodium ion (+)…
  2. 2…attracts the slightly negative oxygen ends of water (Water and Ethanol, Figure 2).
  3. 3A chloride ion (−) attracts the slightly positive hydrogen ends instead. Surrounded this way, the ions drift apart: salt dissolves.

This is how sodium and chloride travel in blood and the fluid around your cells. Where sodium goes, water follows, so sodium sets how much fluid is outside your cells.

Sodium

In your body: The main positive ion in the fluid outside cells: keeps fluid volume and blood pressure steady, and carries nerve signals with potassium. Adequate intake 1,500 mg a day.

Too little: Rare from diet. Low blood sodium usually comes from illness, some medicines, or drinking very large amounts of water during endurance exercise.

Too much: Raises blood pressure in many people, which increases the risk of heart disease and stroke. US guidance is to reduce intake if above 2,300 mg a day; most Americans eat about 3,400 mg.

Found in: Small amounts in most foods: celery, beets, milk, eggs, shellfish. Most dietary sodium comes from salt added in processing, restaurants and cooking.

Chloride, and stomach acid

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  1. 1Your stomach makes hydrochloric acid, HCl, from chloride in the blood. In water it splits into H⁺, which makes the stomach acidic, and Cl⁻.

In your body: The main negative ion outside cells, paired with sodium; needed for stomach acid. Adequate intake 2,300 mg a day.

Too little: Rare; can follow prolonged vomiting.

Too much: Comes with salt; the concern is the sodium.

Found in: Salt, seaweed, tomatoes, celery, olives.

sodium chlorine hydrogen oxygen · every molecule on this page is drawn at the same scale with every hydrogen shown · tap one to enlarge it

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Figure 4

Potassium

The ion inside your cells.

Potassium

Potassium chloride, KCl

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  1. 1The same grid as table salt, with larger potassium ions in place of sodium. Potassium chloride is the main ingredient of “salt substitutes”; it tastes salty with a bitter edge.
Sodium outside, potassium inside
  1. Inside cellsabout 98% of your potassium is inside cells
  2. Outside cellsmost sodium stays in the fluid around them
  3. The sodium-potassium pumpa protein in every cell membrane pushes 3 Na⁺ out and brings 2 K⁺ in, using energy from ATP
  4. Why it mattersthe difference in charge across the membrane lets nerves fire, muscles contract and the heart beat steadily

Potassium

In your body: The main positive ion inside cells; helps control heartbeat, muscle and nerve signals, and blunts the effect of sodium on blood pressure. Adequate intake 3,400 mg (men), 2,600 mg (women).

Too little: Low intake is common and linked with higher blood pressure. Very low blood potassium, usually from vomiting, diarrhea or some diuretics, causes weakness and irregular heartbeat.

Too much: Healthy kidneys remove extra potassium from food. In kidney disease, or with some blood-pressure medicines, it can build up and disturb the heart rhythm, so salt substitutes and supplements need a doctor’s advice.

Found in: Beans, lentils, potatoes, sweet potatoes, squash, spinach, bananas, dried apricots, avocado, yogurt.

potassium chlorine · every molecule on this page is drawn at the same scale with every hydrogen shown · tap one to enlarge it

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Figure 5

Calcium

Bones, teeth and a steady blood level.

Calcium

Calcium carbonate, CaCO₃

Calcium ionCa²⁺

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Calcium carbonateCaCO₃

  1. 1A calcium ion (2+)…
  2. 2…paired with carbonate, CO₃²⁻ (2−). Calcium carbonate is chalk, limestone, eggshell and seashell, and the most common calcium supplement. In the stomach, acid frees the calcium ion.
Where your calcium is
Bones and teeth: about 99%Calcium and phosphate form hard crystals (hydroxyapatite) on a collagen frame.
Blood and cells: about 1%Used for muscle contraction, nerve signals, blood clotting and hormone release.
Bone is a bankBlood calcium is held in a narrow range. When intake is low, hormones (with active vitamin D) take calcium from bone, so low intake shows up years later as weak bones.

Calcium

In your body: RDA 1,000 mg for adults 19–50 and men 51–70; 1,200 mg for women over 50 and men over 70. Vitamin D is needed to absorb it (Fat-Soluble Vitamins, Figure 4).

Too little: Over time, low bone mass and osteoporosis, with a higher risk of fractures.

Too much: Above the upper limit (2,500 mg a day up to age 50; 2,000 mg after), usually from supplements: constipation and kidney stones.

Found in: Yogurt, milk, cheese, sardines and canned salmon with the bones, tofu made with calcium sulfate, kale, bok choy, collard greens, almonds. Spinach is high in calcium but its oxalate binds most of it (Antinutrients).

calcium carbon oxygen · every molecule on this page is drawn at the same scale with every hydrogen shown · tap one to enlarge it

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Figure 6

Phosphorus and Magnesium

Phosphate in bone and ATP; magnesium for enzymes.

Phosphorus

Phosphate

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PhosphatePO₄³⁻

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Hydrogen phosphateHPO₄²⁻

  1. 1Phosphorus (orange) with four oxygens. In the body, phosphorus is almost always found as phosphate.
  2. 2At the pH of blood, much of it carries one hydrogen.

In your body: About 85% is in bone, with calcium. Phosphate is also part of DNA, of the phospholipids in every cell membrane (Lipids) and of ATP, the cell’s energy carrier. RDA 700 mg.

Too little: Rare from diet; occurs in some illnesses and with long-term heavy antacid use: weakness, bone pain.

Too much: In kidney disease phosphate builds up and harms bones and blood vessels. Upper limit 4,000 mg (3,000 mg over 70).

Found in: Protein foods: dairy, meat, poultry, fish, eggs, beans, lentils, nuts. Whole grains and seeds contain it as phytate, which is less well absorbed (Antinutrients).

Magnesium

Magnesium ion in water, Mg(H₂O)₆²⁺

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  1. 1Magnesium is small and doubly charged…
  2. 2…so it holds its water molecules tightly, much more than sodium does (Figure 3).

In your body: About half is in bone. Needed by over 300 enzymes; ATP works mostly as a magnesium–ATP pair. Also for muscle and nerve function and heart rhythm. Magnesium sits at the center of chlorophyll, which is why green vegetables supply it. RDA 400–420 mg (men), 310–320 mg (women).

Too little: Many people eat less than the RDA; a true deficiency is uncommon but causes muscle cramps, weakness and irregular heartbeat.

Too much: No harm from food. Supplements above 350 mg a day can cause diarrhea; larger amounts are dangerous with kidney disease.

Found in: Pumpkin seeds, chia seeds, almonds, cashews, spinach, black beans, edamame, whole grains, dark chocolate.

magnesium phosphorus oxygen hydrogen · every molecule on this page is drawn at the same scale with every hydrogen shown · tap one to enlarge it

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Figure 7

Sulfur

In protein: methionine, cysteine and sulfate.

Sulfur

The sulfur amino acids

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Methionineessential

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Cysteinemade from methionine

  1. 1Methionine: sulfur (yellow) in the middle of its side chain. It’s essential: you must eat it.
  2. 2Cysteine: an SH group at the end. Two cysteines in a protein can join S–S, a disulfide bridge that holds proteins such as keratin in shape (Protein, Figure 5).

Sulfate, SO₄²⁻

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  1. 3Your body turns extra sulfur from amino acids into sulfate, used to build cartilage and to help the liver clear some drugs, and passes the rest in urine.

What it is: The third most plentiful mineral in the body by weight, after calcium and phosphorus.

In your body: Part of methionine and cysteine, of glutathione (a major antioxidant inside cells), and of thiamin and biotin (Water-Soluble Vitamins).

Too little: There is no separate requirement: enough protein supplies enough sulfur.

Found in: Eggs, meat, fish, dairy, beans, nuts; garlic, onions and cabbage-family vegetables also contain sulfur compounds that give them their smell (Bioactives).

carbon hydrogen oxygen nitrogen sulfur · every molecule on this page is drawn at the same scale with every hydrogen shown · tap one to enlarge it

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Figure 8

Salt and the Label

Daily Values, and salt versus sodium.

Major minerals on the Nutrition Facts label
On the labelDaily ValueNotes
Sodium2,300 mgrequired on every label
Potassium4,700 mgrequired since the 2016 update
Calcium1,300 mgrequired since the 2016 update
Phosphorus1,250 mgonly if added or claimed
Magnesium420 mgonly if added or claimed
Chloride2,300 mgonly if added or claimed
Salt and sodium
Salt is about 40% sodiumSodium chloride is 39% sodium by weight. A teaspoon of salt (about 6 g) has about 2,300 mg of sodium, a whole day’s Daily Value.
Sea salt, kosher salt, pink saltAll are mostly sodium chloride, with the same sodium per gram. Coarse crystals pack less tightly, so a teaspoon can hold less.
Where it comes fromMost sodium in US diets comes from packaged and restaurant foods rather than the salt shaker; cooking from whole foods makes intake easier to control.
Reading the % Daily Value
5% or less is lowA food with 5% DV or less of sodium is low in sodium; 20% or more is high.
Potassium and calciumThe same 5% / 20% guide works the other way round for nutrients you want more of.
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Figure 9

Where major minerals are used in the body

Tap a number on the cell to see what that part does; the list below it gives every other place in the body.

Calcium, phosphorus and magnesium build bone; sodium, potassium and chloride carry the electric signals.

Inside a cell

A typical animal cell, not to scale. Real cells hold thousands of ribosomes and hundreds of mitochondria.

Sodium, potassium, calcium, magnesium, phosphorus and chloride drive the cell's signals and energy.

  1. The sodium-potassium pump keeps sodium out and potassium in; that difference powers nerve signals and nutrient uptake.
  2. Stores calcium and releases it as a signal; in muscle, this store (the sarcoplasmic reticulum) triggers contraction.
  3. Phosphate is part of ATP; magnesium has to be bound to ATP for most enzymes to use it.
  4. Phosphate forms the backbone of DNA and RNA.
  5. Magnesium helps more than 300 enzymes; chloride balances charge.
  6. Magnesium holds ribosome RNA in shape so it can make protein.

Everywhere else in the body

Each item, the places outside the cell where it is found or used, and what it does there.

Calcium

  • Bones and teeth. Hold about 99%, as calcium phosphate (hydroxyapatite); bone is also a bank the blood draws on.
  • Blood. Kept in a narrow range; also needed for clotting.
  • Parathyroid glands. Sense blood calcium and release PTH when it falls.
  • Thyroid gland. Its C cells release calcitonin, which lowers it a little.
  • Muscle. Triggers every contraction.
  • Heart. Each beat starts with calcium flowing in.
  • Nerves. Calcium lets nerve endings release their signals.
  • Small intestine. Absorbs calcium with help from vitamin D.
  • Kidneys. Take back most filtered calcium; calcium is part of most kidney stones.
  • Breast milk. Carries calcium to the baby.

Phosphorus

  • Bones and teeth. Hold about 85%, in calcium phosphate.
  • Blood. Phosphate helps buffer acid.
  • Red blood cells. A phosphate compound (2,3-BPG) helps hemoglobin let go of oxygen.
  • Kidneys. Keep the level steady, guided by FGF23 from bone and PTH.

Magnesium

  • Bones. Hold over half.
  • Muscle and soft tissue. Hold most of the rest; needed for relaxing after contraction.
  • Heart. Helps keep a steady rhythm.
  • Nerves. Calms nerve excitability.
  • Parathyroid glands. Need magnesium to release PTH.
  • Kidneys. Keep the blood level steady.

Sodium

  • Blood and the fluid between cells. The main positive ion outside cells: holds water there and sets blood volume and pressure.
  • Nerves and muscle. Sodium rushing in starts every nerve signal and muscle contraction.
  • Kidneys. Adjust how much they keep, guided by aldosterone from the adrenal glands.
  • Small intestine. Sodium and glucose are absorbed together, which is how oral rehydration solution works.
  • Bone. Holds a store of sodium.
  • Skin. Sweat carries sodium out.

Potassium

  • Muscle. Holds most of the body’s potassium.
  • Heart. Both too little and too much in the blood disturb its rhythm.
  • Nerves. Potassium flowing out resets each signal.
  • Kidneys. Send extra out; aldosterone speeds this.
  • Blood. Kept in a narrow range; only about 2% of body potassium is outside cells.

Chloride

  • Stomach. Its lining makes hydrochloric acid.
  • Blood. The main negative ion outside cells.
  • Red blood cells. Swap chloride for bicarbonate to help carry carbon dioxide.
  • Airways and gut. Chloride channels keep mucus watery; when they fail, mucus thickens (cystic fibrosis).
  • Skin. Sweat carries chloride out with sodium.

Sulfur

  • Hair, nails and outer skin. Keratin is held together by sulfur bridges.
  • Cartilage. Chondroitin sulfate holds water.
  • Liver. Uses sulfur in glutathione and to tag drugs and wastes for removal.
  • Bile. Taurine, a sulfur compound, is joined to bile acids.
  • Pancreas. Insulin is held in shape by sulfur bridges.
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Figure 10

Putting It All Together

The whole lesson in one table, plus a few extras.

The seven major minerals
MineralMain jobsToo little / too muchWhole-food sources
Sodium (Na⁺)fluid volume, nerve signalsrarely short / raises blood pressuresmall amounts in many foods; mostly from added salt
Chloride (Cl⁻)fluid balance, stomach acidrare / comes with sodiumsalt, seaweed, tomatoes, celery
Potassium (K⁺)heartbeat, nerves, muscles, blood pressurelow intake common / risk only with kidney diseasebeans, potatoes, squash, leafy greens, bananas
Calcium (Ca²⁺)bones, teeth, muscles, clottingweak bones / kidney stones from supplementsdairy, sardines, tofu, kale, bok choy
Phosphorus (phosphate)bones, DNA, membranes, ATPrare / harmful in kidney diseasedairy, meat, fish, beans, nuts
Magnesium (Mg²⁺)300+ enzymes, ATP, musclescramps, irregular heartbeat / diarrhea from supplementsseeds, nuts, greens, beans, whole grains
Sulfursulfur amino acids, glutathionecovered by protein / —eggs, meat, fish, beans, onions, garlic
Worth knowing

Minerals can’t be cooked away

Heat doesn’t destroy minerals, but boiling leaches potassium and some magnesium into the water; soups keep it.

Hard water

Hard tap water carries dissolved calcium and magnesium, and can supply a useful share of them.

Bones keep changing

Bone is living tissue, remodeled throughout life; weight-bearing exercise, calcium, vitamin D and protein all help keep it strong.

General education, not medical advice. Facts follow mainstream sources (US Dietary Guidelines, NIH Office of Dietary Supplements, standard biochemistry and food-science texts).

Quiz

Tap a question to see the answer

1. What makes a mineral “major” rather than “trace”?

You need it in amounts over about 100 mg a day; it is not about importance (Figure 1).

2. Why is a sodium ion positive?

It has given away one electron, so it has one more proton than electrons (Figure 2).

3. Which is larger, a sodium ion or a chloride ion?

Chloride (Figure 2).

4. Which end of a water molecule faces a sodium ion?

The slightly negative oxygen end (Figure 3).

5. What acid does your stomach make from chloride?

Hydrochloric acid, HCl (Figure 3).

6. Where is most of your potassium, inside or outside cells?

Inside, about 98% (Figure 4).

7. What does the sodium-potassium pump do?

Pushes 3 sodium ions out and brings 2 potassium ions in, using ATP (Figure 4).

8. What share of your calcium is in bones and teeth?

About 99% (Figure 5).

9. Name three things phosphate is part of besides bone.

DNA, phospholipids in membranes, ATP (Figure 6).

10. Why are green vegetables a good source of magnesium?

Magnesium is at the center of chlorophyll (Figure 6).

11. Which two amino acids contain sulfur?

Methionine and cysteine (Figure 7).

12. About how much sodium is in a teaspoon of salt?

About 2,300 mg, a full day’s Daily Value (Figure 8).

Next lesson: Module 2 · Trace Minerals →