The Siege You Were Never Told About

Your body has been withholding iron from bacteria — and from you — for four hundred million years

If you are a X-men movie fan, you will know a scene.

Mystique seduces a prison guard in the bar and drops something into his drink. The guard feints out and she injects a metallic liquid to the guard through the syringe. Several, hours later the guard walks a catwalk in a facility built entirely of plastic, above the cell where Magneto is being held.

All of sudden, Magneto raises his hands and irons are being pulled out from guard’s body by penetrating his skin.

From here, we all know that Magneto use those to make a stepping stones and walks out of the jail, easily.

Image courtesy of 20th Century Fox

Yet, let’s dig deeper into an important question.

Why did she have to spike the guard?

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Three grams, all of it locked

The human body already holds three to four grams of iron, most of it inside hemoglobin — the reason blood is red. But none of it was free, which is why Magneto could not reach for it without Mystique’s help.

The iron was there. It was just not his to take.

Not three grams, but zero. Every atom of iron is held inside hemoglobin, inside the storage protein called ferritin, clamped into transferrin as it moves through the plasma.

Estimates of what remains loose diverge by six orders of magnitude depending on which review you open, some putting it near 10⁻¹⁸ M and some near 10⁻²⁴ M. Either figure lands twelve to eighteen orders of magnitude below the micro-molar concentrations a bacterium needs to metabolize and divide.

The reviews cannot agree, and it does not matter. Both numbers say the same thing: there is nothing here to eat.

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Feed them and they wake

It is equally essential to everything that arrives to kill us — bacteria need it to respire, to replicate, to build DNA. Two claims on the same three grams, and only one of them is yours. Your body has been arbitrating that claim your whole life without telling you the terms.

Take away the food.

In 1975, the microbiologist Eugene Weinberg gave a name to this finding - nutritional immunity.¹ While accepted today as standard infection physiology, the concept seemed counterintuitive at the time, when medicine was primarily defined by the practice of feeding sick patients.

Indeed, the bill for that flawed assumption was already coming due.

In 1978, Michael and Abby Murray treated severely malnourished, anemic, and iron-depleted Somali nomads in a famine camp. Following the standard medical logic at that time, they prescribed iron supplements.

Yet, this trigged a catastrophic result: Brucellosis, malaria, and tuberculosis resurged among the treated patients. The Murrays had not uncovered a cure for malnutrition; rather, they revealed that nutritional deprivation served as a biological defense mechanism that suppresses latent infections.

Twenty-eight years later, a large pediatric iron and folic acid trial on Pemba, in Zanzibar, was stopped early: in a setting where malaria is always present, children given iron were hospitalized and died at higher rates. The trial did not conclude. It was halted.

Both studies made the same design error. They saw a body with no available iron and read deficiency.

The body was not deficient. It was withholding.

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The only way out

Withholding is a physical act.

Iron does not float; it is handed from cell to cell, and every handoff goes through the same protein.

Ferroportin is the only way iron leaves a cell and enters the blood — the gut lining uses it, the macrophages recycling old red cells use it.

Which makes it the only thing you have to close.

A small peptide hormone synthesized in the liver does the job. When the body encounters infection or inflammation, hepcidin² finds ferroportin, dragging it into the cell and destroying it.

It is not a lock on the door. It is the door taken off its hinges.

And it takes hours.

Iron from the gut cannot leave the cell, and iron recovered from the old red blood cells cannot leave. Serum iron level will indeed fall again, so whatever is trying to grow in our body - the invaders - will eventually finds an empty pantry.

The marrow building red blood cells is also waiting at that port, and when the port is gone the marrow starves too. The anemia that shadows chronic infection, autoimmune disease, cancer and kidney failure — anemia of inflammation³ — is not damage the illness inflicted. It is an invoice for a defense the body chose. Correcting the anemia and lifting the siege are the same act.

The body starves its own marrow in order to starve something else, and it does not consult us.

It has been making that trade for four hundred million years.

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Four hundred million years of practice

Indeed, Bacteria never bothered with magnetism.

They built better instruments.

• Staphylococcus aureus ruptures red cells and tears the heme out of the spilled hemoglobin — a thief who breaks the safe and empties it by hand.

• Neisseria grew receptors shaped to human transferrin and drinks from the armored car without stopping it.

• Salmonella coats its scavenging molecules in sugar so the immune protein sent to seize them cannot get a grip, which is smuggling.

Three ways into the same vault: break it, tap the delivery, forge the paperwork.

Borrelia did something else. The organism that causes Lyme disease runs on manganese and barely touches iron — it left the war rather than fight it. A siege only works on someone who still wants the commodity

The finest instrument is the siderophore⁴, a molecule secreted for no purpose but to hunt loose iron.

Enterobactin, made by E. coli, holds iron more tightly than human transferrin does. It does not break the lock. It reaches past it and takes what transferrin is already holding.

Bacteria can pull iron out of a living human body.

Which is what Magneto was trying to do.

His target was right; His instrument was wrong.

The iron in hemoglobin is not the kind a magnet recovers — it is faintly magnetic at best, so faint that MRI reads the difference between oxygenated and deoxygenated blood and turns it into a picture of a working brain.

Physics beats him decisively. Hence the syringe.

The bacteria never needed one. And neither does your body, which has been making the same calculation about you since before you were born — how much iron to release, how much to hold back, and who goes hungry when it holds.

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The body built no exit

The calculation can fail in the other direction too.

Let’s consider a vampire.

A vampire lives on other people’s blood. The stopped heart is not a universal rule of the genre — Stoker says nothing about it, and the convention mostly hardened over the last century. Concede that. What survives the concession is that the writers who chose it chose better than they knew.

A unit of transfused red cells carries roughly 200 to 250 milligrams of iron. A person loses about one milligram a day, in sweat and shed intestinal cells, and that is the whole of it. There is no organ for getting rid of iron.

The kidney does not excrete it; the liver cannot break it down.

For four hundred million years iron was too scarce to be worth a disposal system.

So in a body kept alive by lifelong transfusion, iron only ever arrives. When the stores overflow it deposits in the liver, in the endocrine organs, and in cardiac muscle. Before chelation⁵ became routine, the leading cause of death in severe thalassemia was not anemia. It was iron-loaded myocardium losing its rhythm, usually in the second or third decade of life.

Take in blood forever and the heart stops.

The fiction had the wrong cause and the right outcome.

Set the two stories side by side

Magneto is acute theft, the vampire is chronic accumulation.

One is a story about breaching the siege, the other about having too much to keep under guard. The survivable range is narrow — fall below it and the marrow dies, rise above it and the heart does.

Four hundred million years ago your body decided iron was too precious to throw away. It was right, and nobody has revisited the decision since.

It also assumed the door would always close on command.

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One plate, two men

There are raw oysters on the table. Two people share the plate.

Two days later one of them is fine and the other one is dead.

Oysters carry Vibrio vulnificus, a bacterium native to warm coastal water. In most people it causes a bout of gastroenteritis and nothing more. In the wrong body it reaches the bloodstream within hours, and the septicemic form kills about half the people it infects, inside two days.

Hereditary hemochromatosis⁶ comes from a single letter in the HFE gene. Inherit the C282Y variant from both parents and you do not make enough hepcidin. The order to close the port never arrives. The gut keeps releasing what it absorbs, and iron accumulates across decades in the liver, the heart, the pancreas. Among people of northern European descent, roughly one in a few hundred carries that genotype. This is not a rare disease.

And in that man, free iron is not zero. The number this whole piece was built on collapses here.

His transferrin is saturated and the excess circulates loose in his plasma. The bacterium does not need a siderophore. It does not need to rupture a red cell, does not need a disguise, does not need four hundred million years of instruments. The place all of that was trying to reach, it simply arrives at.

The pantry is a buffet.

He almost certainly does not know he is different. Hemochromatosis is silent for years, and when it speaks it says fatigue and sore joints, which is what everything says. He has never been tested. Until the diagnosis he is a fifty-six-year-old man who likes oysters.

X-Men was never about magnetism. It was about registries — who gets written down, who gets counted as a different kind of body. The comics asked it in the language of registration acts and camps. Medicine asks it more quietly, in ferritin levels and transferrin saturation and a genetic test nobody ordered.

He was not on the list. To the bacterium this made no difference at all.

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<Mattheus van Bree - The Self-Sacrifice of Burgomaster van der Werff> Leiden, 1574. The city chose starvation over surrender.

“Ubi solitudinem faciunt, pacem appellant.” 
Where they make a desert, they call it peace. — Tacitus, Agricola (c. 98 AD)

Mystique had to use the syringe, and the reason was never that the prison was plastic. It was that the guard's body had been conducting a siege since long before either of them was born, and the terms were not negotiable by anyone in that building.

There was always a list. Not the one the comics were afraid of — this one is older, it is kept in ferritin and transferrin saturation, and everybody is on it. Most of us are simply in the column where nothing happens.

Our bodies decided to starve themselves in order to starve something else, and none of us was consulted. We only ate the oysters.

Two people, one plate.

In one of them there was nothing to find.

In the other one there was.

1. Nutritional immunity — the host defense of sequestering essential metals such as iron, zinc and manganese to deny them to invading microbes.

2. Hepcidin — a peptide hormone made in the liver that lowers serum iron by degrading ferroportin, the body’s only iron export protein.

3. Anemia of inflammation — anemia arising when iron is locked in storage and unavailable to the marrow. Treated differently from iron-deficiency anemia.

4. Siderophore — a small molecule secreted by bacteria to capture iron, often binding it more tightly than host proteins can.

5. Chelation — drug treatment that binds excess metal in the body so it can be excreted.

6. Hereditary hemochromatosis — a genetic disorder of iron regulation causing progressive overload; the HFE C282Y variant is the most common cause.