Ferritin Doesn't Measure Iron — Dr Douglas Kell on Iron Dysregulation and Chronic Disease
Douglas Kell argues that ferritin in your plasma is not an iron measurement at all — it is a signal that cells have died and released their stored iron. Once that iron is free and unbound, it fuels the Fenton reaction, generates hydroxyl radicals, and sets off a self-amplifying loop of oxidative stress and inflammation. The practical layer: look at transferrin saturation, keep iron bound, and pay attention to compounds like ergothioneine from mushrooms.
Overview
Dr Douglas Kell, a systems biologist at the University of Liverpool, works with Professor Resia Pretorius on a unifying account of chronic inflammatory disease built around iron. His starting point overturns a common assumption: ferritin is an intracellular storage molecule that has no business being in plasma, so a raised plasma ferritin reading reflects cell death rather than iron status. When cells die they release iron in a free, unliganded form, and free ferrous iron reacts with hydrogen peroxide in the Fenton reaction to produce the hydroxyl radical — in Kell's framing, the real driver of oxidative stress.
Free iron also does something else: it wakes dormant bacteria that most of us carry quietly, and those waking microbes release inflammatory molecules such as lipopolysaccharide. Those molecules, in vanishingly small amounts, flip normal fibrinogen clotting into an anomalous amyloid form, producing fibrinaloid microclots that block the smallest capillaries and starve tissue of oxygen. That hypoxia kills more cells, which release more ferritin — a positive feedback loop Kell sees echoed across long COVID, ME/CFS, rheumatoid arthritis, Alzheimer's, Parkinson's, diabetes and preeclampsia.
On the measurement side he points away from ferritin and toward transferrin and transferrin saturation, plus the classical oxidative stress markers. On the practical side he highlights iron-binding and Nrf2-activating compounds — ergothioneine from culinary mushrooms above all, alongside green tea catechins, sulforaphane and kynurenic acid — and proteolytic enzymes such as nattokinase and serrapeptase. He is candid that the fuller hypothesis still needs randomised trials, and equally candid that he is a scientist, not a clinician.
Key quotes
5When people measure ferritin thinking it's got something to do with iron, it has nothing to do with iron whatsoever. It is a marker of cell death.
The bad guy is the hydroxyl radical.
The reason bugs don't grow in you normally is that there's no free iron.
Transferrin-bound iron, or the percentage of transferrin that has iron attached to it — these are the measurements that are relevant.
If you have one mushroom portion per week you halve the likelihood of mild cognitive impairment. Nine portions a week and you decrease it fivefold.
Key ideas
9Iron speciation is the whole story
What matters is not how much iron you have but what form it is in and whether all six of its binding sites are occupied. Fully bound iron is inert; partially bound or free iron is chemically aggressive.
The Fenton and Haber-Weiss cycle
Free ferrous iron reacts with hydrogen peroxide to make hydroxyl radicals, then superoxide converts it back so the cycle repeats. That catalytic loop is what turns a small amount of loose iron into sustained oxidative damage.
Ischaemia and reperfusion feed the loop
When tissue is short of oxygen the mitochondria become over-reduced, so returning oxygen is converted into peroxide and superoxide instead of water. With free iron present, that surge becomes a burst of hydroxyl radicals.
Ferritin in plasma means cells died
Ferritin is an intracellular sphere holding up to 4,000 iron atoms. Its presence in plasma, where no cells exist, indicates cell rupture — and the iron it once held has already been liberated.
A dormant microbiome we all carry
Bacteria survive lean conditions by entering a dormant state that standard culture plates cannot detect. Kell describes a dormant blood microbiome that free iron can resuscitate, releasing inflammatory molecules once it does.
Fibrinaloid microclots
In the presence of free iron or lipopolysaccharide, fibrinogen polymerises into an amyloid form rather than the usual spaghetti-like fibres. These clots resist plasmin, so the body cannot clear them normally.
Amyloid spreads by cross-seeding
One amyloid-prone protein can flip others into the same insoluble state, which is why the protein profile of these microclots is enriched in amyloidogenic proteins that are otherwise scarce in plasma.
Ergothioneine keeps winning
In a Swedish study of 3,000 people, ergothioneine was the blood metabolite most strongly associated with not having a heart attack in the following three years. It works largely by activating Nrf2 and its antioxidant response elements.
A systems view, not a single gene
Kell's argument is that chronic inflammatory conditions share one machinery expressed in different tissues. Understanding it means mapping the actors and their feedback loops rather than chasing one favourite molecule.
Practical takeaways
7- 1
Ask about transferrin saturation 22:20
If you review iron on a blood panel, transferrin and transferrin saturation carry more information than ferritin alone. Discuss the full panel with your own clinician.
- 2
Read a high ferritin as a flag, not a verdict 10:00
Raised plasma ferritin is worth noticing as a signal of cell turnover and inflammation. It is a prompt for a conversation, not a self-diagnosis.
- 3
Put mushrooms on the plate regularly 31:00
All culinary mushrooms contain ergothioneine, and we evolved a dedicated transporter for it. Regular portions are an easy, food-first way to keep intake up.
- 4
Broaden the plant compounds 33:00
Green tea catechins and sulforaphane from brassicas also support the same antioxidant response pathway. Variety across these foods is more useful than fixating on one.
- 5
Don't reach for iron supplements by default 40:10
Kell notes that most people are not short of total iron — the problem is usually the form it is in. Any supplementation decision belongs with a clinician who has your labs.
- 6
Keep the everyday levers loaded 43:20
Good diet, sleep and exercise are what keep the seesaw tilted toward resolution rather than smouldering inflammation. The goal is well-regulated inflammation, not zero.
- 7
Know the oxidative stress markers 45:30
Oxidised DNA, protein and lipid all leave measurable traces, and they tend to move together. They are the practical window into the process Kell describes.
Topics & chapters
15The claim that reframes ferritin
The host previews the conversation: ferritin measures cell death, not iron, and transferrin saturation is the more informative test.
Meet Dr Douglas Kell
Kell introduces his systems biology work at Liverpool and his long-running collaboration with Professor Resia Pretorius.
Iron speciation and the Fenton reaction
Why the form of iron matters more than the amount, and how free ferrous iron generates hydroxyl radicals through a self-renewing catalytic cycle.
Hypoxia, reperfusion and cell death
Oxygen returning to under-oxygenated tissue produces reactive species, cells die, and their stored iron is released.
What ferritin actually tells you
Ferritin's role as an intracellular storage sphere, and why its appearance in plasma is a cell-death signal rather than an iron reading.
Dormant bacteria and free iron
Most of us carry dormant microbes that stay quiet because iron is bound. Free iron can wake them, and awakened microbes release inflammagens.
How normal clotting turns amyloid
Fibrinogen polymerisation explained, and how iron or bacterial molecules push it into a dense, matted, amyloid form.
Which iron test to actually run
Transferrin and transferrin saturation replace ferritin as the meaningful measurements of iron transport.
What starts the cascade
Infection, trauma and ischaemia-reperfusion release ferritin and iron, opening a positive feedback loop between clotting, hypoxia and further cell death.
Ergothioneine and mushrooms
The Swedish cohort finding, the dedicated human transporter, the Nrf2 mechanism, the preeclampsia association — plus green tea catechins, kynurenic acid and sulforaphane as further candidates.
Alzheimer's, long COVID and the microcirculation
Kell's view that several chronic conditions share the same microclot and microcirculation story expressed in different tissues.
Amyloid explained and stroke clots
What amyloid means in plain terms, why the form resists breakdown, and what was found inside clots retrieved after ischaemic stroke.
Markers you can actually measure
The classical oxidative stress markers for DNA, protein and lipid damage, and the circularity of inflammation markers.
Chelators, systems medicine and enzymes
Prescription iron chelators, the systems view drawn from traditional practice, and proteolytic enzymes such as nattokinase and serrapeptase.
Where the research goes next
Mapping microclot proteomes for diagnosis and funding trials in long COVID, ME/CFS and preeclampsia.