Aluminium: the pathway in the body · Biomarker & Laboratory Analysis

This page shows the biochemical pathway of the substance Aluminium: how it enters the body, which stations it passes and which steps it affects. Every statement has a source. The page describes general textbook knowledge and says nothing about any individual person.

In brief

Aluminium is a light metal and the most common metal of the earth's crust. In the body it is present as a trivalent ion, binds to transferrin in the blood and is excreted mainly by the kidney. It occupies binding sites of magnesium and iron.

The pathway step by step

Each station states what the compound does there. Three signs: ↑ supplies — builds up or makes available · ↓ depletes — inhibits, consumes or withholds · ↕ both, depending on amount. Behind it stands what the statement rests on: established physiology, observed in studies, or contested. The signs do not grade; they name the direction.

1. Environmental aluminium → In the digestive tract In the acidic stomach part of the aluminium dissolves into trivalent ions. In the gut, phosphate binds aluminium into poorly soluble compounds; citrate keeps it dissolved. Bound aluminium leaves the body with the stool. Source 1, 3↓ depletes In the gut, phosphate withdraws dissolved aluminium from absorption: poorly soluble compounds form that leave with the stool. Citrate, by contrast, keeps part of it dissolved and thus available. established physiology Source 1, 3
   ⚖ When the balance tips

   too much — If a lot of dissolved aluminium is present in the gut, for example together with citrate, more of it crosses the gut wall; aluminium bound to phosphate leaves with the stool instead.

   too little — If little dissolved aluminium is in the gut, for example because plenty of phosphate binds it, hardly any reaches the blood; the rest leaves the body with the stool.

   established physiology · Source 1, 3

2. In the digestive tract → Across the gut wall · Citrate Only a small share of the aluminium crosses the gut wall into the blood, partly by passing between the cells. The rest stays in the gut. Source 1↑ supplies Passage through the gut wall determines how much aluminium enters the body at all; it is small and partly occurs between the cells. established physiology Source 1
   ⚖ When the balance tips

   too much — If more aluminium passes across, for example because citrate keeps it dissolved and loosens the junctions between the cells, the amount in the blood rises.

   too little — If little passes across, most of it stays in the gut and leaves the body with the stool.

   observed in studies · Source 1

3. Across the gut wall → Aluminium in the blood · Transferrin In the blood aluminium binds mainly to transferrin, the transport protein of iron. A smaller part is dissolved as a citrate compound. Transferrin carries it to the tissues. Source 3, 2↑ supplies Transferrin keeps aluminium bound in the blood and delivers it to tissues with transferrin receptors; the part bound to citrate is small enough to be filtered by the kidney. established physiology Source 3, 2
   ⚖ When the balance tips

   too much — If more aluminium enters the blood, it occupies more free iron sites on transferrin; the citrate-bound share rises too, and the kidney filters more of it.

   too little — If there is little aluminium in the blood, it is shared between transferrin and citrate in the same way, only in smaller amounts; tissues and kidney then receive correspondingly little.

   established physiology · Source 3, 2

4. Aluminium in the blood → Deposition in bone Part of the aluminium is deposited in bone, where it is bound in the mineral matrix of calcium and phosphate. There it stays stored for a long time. Source 1↓ depletes Bone mineral withdraws aluminium from the blood and holds on to it for a long time; bone is one of the main stores of aluminium in the body. established physiology Source 1
   ⚖ When the balance tips

   too much — If a lot of aluminium is deposited in bone, it stays there for years and is slowly released back into the blood during bone remodelling.

   too little — If little is deposited, bone remains a small store, and hardly any aluminium is resupplied from it.

   established physiology · Source 1

5. Into the cell → Trivalent ion Inside the cell aluminium is present as a trivalent ion. It binds preferentially to oxygen atoms, for example to phosphate groups of ATP and other molecules. There it occupies binding sites of other ions. Source 4, 2↓ depletes As a small, triply charged ion, aluminium occupies oxygen binding sites on phosphate groups firmly and releases them only slowly; it thus withdraws them from other ions. established physiology Source 4, 2
   ⚖ When the balance tips

   too much — If aluminium accumulates in the cell, more phosphate groups of ATP and other molecules are occupied; in laboratory assays reactions that depend on them then run more slowly.

   too little — If there is little aluminium in the cell, these binding sites remain reserved for the cell's own ions such as magnesium.

   observed in studies · Source 4

6. Trivalent ion → Magnesium sites Inside the cell magnesium binds to ATP and to many enzymes. Aluminium binds to the same sites, much more firmly, and is released from them far more slowly. In laboratory assays, reactions that depend on them then run more slowly. Source 4↓ depletes At ATP and enzymes, aluminium displaces magnesium and is released far more slowly; reactions that need a rapid exchange of magnesium then run more slowly in laboratory assays. observed in studies Source 4
   ⚖ When the balance tips

   too much — If aluminium occupies many magnesium sites, fewer of them are free for magnesium; in laboratory assays magnesium-dependent enzymes are then slowed.

   too little — If little aluminium is present, the sites remain almost entirely with magnesium, which is far more abundant in the cell.

   observed in studies · Source 4

7. Magnesium sites → Calcium sites Binding sites for calcium, for example in calcium-binding proteins, can also hold aluminium. In laboratory assays the protein then responds differently to calcium. Source 4↓ depletes In calcium-binding proteins, aluminium can occupy the place of calcium; in laboratory assays the protein then changes its shape and responds differently to calcium signals. observed in studies Source 4
   ⚖ When the balance tips

   too much — If many calcium sites are occupied by aluminium, calcium signals at these proteins are passed on more weakly in laboratory assays.

   too little — If little aluminium is present, these sites remain with the calcium they normally hold.

   observed in studies · Source 4

8. Into the cell → Iron binding sites Aluminium and trivalent iron are similar in charge and size. This is why aluminium binds to the iron binding sites of transferrin. Iron, however, binds there more firmly. Source 3, 2↓ depletes Aluminium occupies iron sites on transferrin that would otherwise stay free; transferrin is usually only partly loaded with iron, so both find room side by side. established physiology Source 3, 2
   ⚖ When the balance tips

   too much — If many iron sites are occupied by aluminium, fewer of them are available for iron; iron, however, binds to transferrin much more firmly than aluminium.

   too little — If little aluminium is present, the free sites on transferrin remain available for iron.

   established physiology · Source 3

9. Iron binding sites → Back into the blood · Citrate From the tissues aluminium returns to the blood. There it forms small, dissolved compounds with citrate. This allows the kidney to filter it. Source 1, 3↑ supplies Citrate turns aluminium into small, dissolved compounds and so makes it available to the kidney for filtration. established physiology Source 1, 3
   ⚖ When the balance tips

   too much — If a lot of aluminium returns from the tissues, the share of citrate compounds in the blood rises, and the kidney excretes more.

   too little — If little is released from the tissues, most of it stays bound there; in bone it can thus remain for a long time.

   established physiology · Source 1, 3

10. Back into the blood → Excretion in urine The small citrate compounds pass the filter of the kidney. Most of the aluminium that has reached the blood leaves the body with the urine. If the kidneys filter more slowly, more stays in the body. Source 1↓ depletes The kidney removes aluminium from the blood and is the main route by which it leaves the body. established physiology Source 1
    ⚖ When the balance tips

    too much — If a lot of aluminium is excreted, the amount in the urine rises quickly with it; part of it nevertheless remains in bone and tissues.

    too little — If the kidneys filter more slowly, aluminium stays in the blood longer, and more of it reaches bone and tissues.

    established physiology · Source 1

Further stations

• Environmental aluminium — food, water, air, skin Aluminium is a common element of the earth's crust. It reaches the gut with food, drinking water and some medicines, and the lungs with dust; only a very small part passes through the skin. No role in the body is known. Source 1, 5↑ supplies Food, drinking water and some medicines supply most of the aluminium that reaches the gut; only a very small part enters the body through the skin. established physiology Source 1, 5
  ⚖ When the balance tips

  too much — If more aluminium reaches the gut, the amount that passes into the blood rises too, although the absorbed share stays small.

  too little — If little aluminium arrives, correspondingly little reaches the blood; no task is known that is then left undone.

  established physiology · Source 1

• Into the cell — via the transferrin route Cells absorb transferrin through its receptor. Aluminium bound to transferrin can enter the cell by the same route. It thus reaches cells that absorb a lot of iron. Source 2, 3↑ supplies Via the transferrin receptor, aluminium enters the cell along the route of iron; in this way it also reaches cells that absorb a lot of iron. observed in studies Source 2, 3
  ⚖ When the balance tips

  too much — If a lot of transferrin is loaded with aluminium, more of it enters the cell via the receptor; in cell studies the amount inside the cell rises accordingly.

  too little — If little aluminium is bound to transferrin, the receptor brings mainly iron into the cell, and hardly any aluminium gets in.

  observed in studies · Source 2

Cofactors in this pathway

• Iron — Aluminium occupies the iron binding sites of transferrin and is carried in the blood this way; iron binds more firmly Source 3, 2In the ORY catalogue as a laboratory value: Eisen
• Magnesium — Aluminium binds to the magnesium sites of ATP and enzymes, more firmly than magnesium itself; released only slowly Source 4In the ORY catalogue as a laboratory value: Magnesium
• Transferrin — Transport protein of iron; binds aluminium in the blood and carries it into cells via its receptor Source 3, 2
• Citrate — Keeps aluminium dissolved in the blood; in this form it passes the filter of the kidney and is excreted Source 1, 3
• Calcium — Calcium binding sites in proteins and in the bone matrix can hold aluminium; it stays there for a long time Source 4, 1
• Phosphate — Forms poorly soluble compounds with aluminium in the gut and in the mineral matrix of bone; these leave with the stool Source 1, 3

Sources

1. Priest ND. The biological behaviour and bioavailability of aluminium in man, with special reference to studies employing aluminium-26 as a tracer: review and study update. J Environ Monit 2004 · PubMed 15152306
2. Exley C, Mold MJ. The binding, transport and fate of aluminium in biological cells. J Trace Elem Med Biol 2015 · PubMed 25498314
3. Harris WR, Berthon G, Day JP et al. Speciation of aluminum in biological systems. J Toxicol Environ Health 1996 · PubMed 8772798
4. Macdonald TL, Martin RB. Aluminum ion in biological systems. Trends Biochem Sci 1988 · PubMed 3072691
5. Flarend R, Bin T, Elmore D et al. A preliminary study of the dermal absorption of aluminium from antiperspirants using aluminium-26. Food Chem Toxicol 2001 · PubMed 11267710

Related pathways

• Nickel — into the cell

As of 2026-09-18. Draft, written by Claude to schema v2; sources checked in PubMed; expert approval pending
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