Minerals

Eleven minerals matter in food. The first seven are measured in hundreds of milligrams a day, the others in milligrams or micrograms. None provides calories: they let the body use the calories of everything else.

These figures come from EFSA, the European authority. France's ANSES holds two slightly different ones, 380 mg of magnesium for men and 1.9 and 1.5 mg of copper: the gap comes from the calculation method, not from a disagreement about the need, and it changes nothing on the plate.

Potassium is the mineral of the inside of cells, sodium the one outside. The difference in concentration between the two creates an electrical tension across every membrane, and that is what the body discharges to fire a nerve impulse or contract a muscle, the heart included. A pump maintains the gap continuously, and it alone consumes a sizeable share of energy at rest.

It has a second role, a trade-off with sodium: when potassium rises, the kidney lets more sodium go, and blood pressure falls. That is why the ratio between the two weighs more on blood pressure than salt taken alone.

What drains it: diuretics, diarrhoea or vomiting, heavy sweating, and the switch to a very low-carb diet, where low insulin raises urinary losses of sodium and then of potassium. What goes missing first shows up as cramps and a muscular fatigue that does not feel like ordinary tiredness.

The 3,500 mg a day is the hardest figure in the table, because no food is genuinely concentrated in potassium: you get there by volume, with vegetables, meat, fish and nuts, not with one miracle food.

Magnesium never works alone: it binds to ATP, the molecule that carries energy, and it is that pair, not bare ATP, that enzymes can use. More than three hundred reactions depend on it, which amounts to saying that every expenditure of energy does.

In muscle, it does the opposite of calcium: calcium triggers contraction, magnesium allows release. When it is short, that release drags, hence night cramps and the twitching eyelid. The rest of its stores, about 60%, sits in bone.

What drains it: alcohol, diuretics, sweat, and once again the diuresis of the first weeks without carbs. Refining removes a lot too, since the bran and germ of grains are the part that holds it.

Ninety-nine percent of the body's calcium is in the skeleton, as crystals that give bone its hardness. The remaining 1%, in blood and cells, does everything else: it triggers every muscle contraction, acts as an entry signal into cells, and allows clotting.

That 1% is held at a constant value, whatever you eat. If intake falls, a hormone fetches calcium where there is some, which means from bone. A lack of calcium therefore never shows in a blood test: it shows up thirty years later, in bone density.

Absorption depends on vitamin D, without which part of the calcium swallowed comes straight back out. Dairy is the densest source, hard cheeses first, ahead of small fish eaten with their bones, seeds and some mineral waters. Whole seeds, though, pass through the gut unopened: they have to be ground, as sesame is into tahini, to give anything up.

Phosphorus accompanies calcium in bone, which the two build together, but its other role is more fundamental still: it is the P in ATP. Every energy transfer in the body is a phosphate changing hands. It also holds the two strands of DNA together and forms the wall of every cell.

It is the only mineral on this page nobody runs short of: it follows protein, so meat, fish, eggs, dairy and nuts supply plenty. The question arises the other way round, with the phosphates added to ultra-processed foods and cola drinks, which raise intake without feeding anyone.

Iron sits at the center of hemoglobin, where it picks up oxygen in the lungs and releases it in tissues. The same atom, in myoglobin, stores that oxygen in muscle, and in the enzymes of the respiratory chain, it helps make energy. When it is short, breathlessness and constant fatigue follow, because transport collapses first.

It comes in two forms with nothing in common when it comes to absorption. Heme iron, from meat, offal and blood sausage, is absorbed at about a quarter. Plant and seed iron much less, often a few percent, because phytates and the tannins in tea latch onto it; vitamin C in the same meal raises that share. So a list of the richest foods is a little misleading: 100 g of blood sausage does more for your iron than 100 g of seeds ranked higher.

What drains it: periods, above all, and that is the only reason the need of the women concerned goes from 11 to 16 mg. Conversely, the body has no way to get rid of excess iron, which makes supplementing without a blood test a genuinely bad idea.

Zinc is an enzyme tool: more than three hundred need it to hold their shape and work. Hence the list of its effects, which looks scattered but has a single cause: immunity, wound healing, DNA synthesis in fast-renewing tissues, testosterone production, taste and smell.

The body keeps no readily mobilized reserve, so it has to be eaten daily. Its absorption is held back by the phytates in whole grains and legumes, so much so that the reference intake is given for a stated phytate level: it climbs to 16 mg for a diet high in them. Zinc from meat and oysters escapes that brake.

Copper is iron's second: a copper enzyme loads iron onto its carrier in the blood. A copper shortage therefore gives an anemia that iron alone does not fix. It also runs the last step of the respiratory chain, the one that consumes oxygen, cross-links collagen and elastin, and makes melanin.

Dietary deficiency is rare, but there is a known trap: zinc supplements, taken long and high, block copper absorption and end up creating one. That is the main argument against extended zinc courses taken for no reason.

Liver is by far the leading source, ahead of oysters, cocoa and nuts.

Sodium holds blood volume and, with potassium, the electrical tension of membranes. It is the only mineral we are repeatedly told to eat less of, and the only one whose need changes sharply with the diet: without carbs, low insulin lets it go in the urine and more is needed, as What changes in the body when you cut carbs explains.

Salt and sodium are not the same thing: table salt is sodium chloride, and 1 g of sodium is 2.5 g of salt. Labels show sometimes one, sometimes the other, hence figures that seem to contradict each other. This site counts salt, as the Ciqual table does. The 2 g of sodium a day benchmark is therefore 5 g of salt, one level teaspoon.

The reality is above that. ANSES measures about 8.7 g of salt a day in men and 6.7 g in women, and more like 10 and 8 g counting the salt cellar and cooking water. The WHO target is 5 g: France sits at nearly twice that.

The salt cellar is not the lever. Most salt is already in food when you buy it, and the PNNS names its three main sources: bread, cheese and cured meats. The database bears this out, cured meats first:

Bread shows why that ranking is not enough. At 1.45 g per 100 g, it is nothing dramatic next to cured ham, but half a baguette brings 1.8 g, more than a third of the day. What counts is the content times the amount eaten, and bread wins on the amount.

Iodine serves one purpose only, but a central one: thyroid hormones, which set the speed at which the whole body burns its energy. Iodized salt, fish, dairy and eggs supply it; a diet with none of the four is the case where the question genuinely arises.

Selenium sits at the heart of the enzymes that neutralize peroxides, and also activates thyroid hormones. The Brazil nut is a case apart, so rich that a single nut covers the day, and that a handful daily ends up supplying too much.

Manganese is involved in bone formation and in the antioxidant enzyme of the mitochondria. Tea, whole grains and nuts supply plenty; dietary deficiency is practically unheard of.

Seeds and nuts are the densest category in the database, first for six minerals out of seven. A handful a day changes the totals.

Potassium is the hardest to reach, for lack of a concentrated food: it comes from the volume on the plate, not from one particular food.

Iron and zinc from meat are far better absorbed than from seeds, which nonetheless post bigger numbers. For those two, the raw ranking misleads.

Calcium does not show in the blood: when intake falls, the body takes what is missing from bone to keep the blood at its set value. Nothing is felt, for years, and the bill arrives late in life as fragile bones.

Without carbs, sodium, potassium and magnesium leave more readily in the urine, during the adaptation weeks above all.

Salt does not come from the salt cellar: it is already in bread, cheese and cured meats. We eat nearly twice the benchmark without ever touching the grinder.

Phosphorus and manganese ask for no attention: ordinary food supplies enough.