Iron deficiency has become one of the most common deficiencies today. Cold hands? Low iron. Constant fatigue? Low iron. Hair shedding, heavy periods, dizziness, breathlessness? Low iron.

The solution is usually swift and unquestioned… take a supplement, eat more spinach, fortify your cereal. And yet, so many of us do exactly that,  eat “iron rich” foods, swallow synthetic tablets for months or years, and still feel exhausted, depleted, and stuck in the same cycle.

So what’s going on? The uncomfortable truth is this… iron deficiency is rarely just about intake. It’s about absorption, utilisation, and regulation, and modern nutrition has misunderstood all three.

Eating iron doesn’t mean absorbing iron

One of the biggest myths around iron deficiency is the idea that eating more iron automatically raises iron levels. It doesn’t.

Iron absorption is tightly regulated by the body. This is because iron is both essential and potentially harmful in excess. Free iron is highly reactive, it can drive oxidative stress, feed pathogens, and damage tissue if not carefully bound and controlled.

So the body only absorbs iron when the internal environment allows for it. You can eat iron-rich foods daily and still be deficient if:

• Stomach acid is low
• The gut lining is inflamed or compromised
• Copper is deficient
• The liver is overburdened
• Inflammation is chronically elevated
• Stress hormones are high
• Iron deficiency is often a downstream signal, not the root problem.

Synthetic iron vs whole food iron

Most iron supplements use isolated, synthetic forms such as ferrous sulfate, ferrous fumarate or ferrous gluconate. These are unbound forms of iron.

Unbound iron enters the body without its natural cofactors. It floats freely, irritating the gut lining, causing nausea, constipation, and oxidative stress. The body recognises this as a threat and often responds by reducing absorption even further.

This is why so many people experience:

• Digestive pain from iron supplements
• Constipation or black stools
• No meaningful rise in ferritin
• Worsening inflammation over time

Whole food iron behaves very differently. Heme iron, found in animal foods, is bound,  packaged within proteins the body recognises and knows how to transport safely. It is absorbed through a separate pathway that is far less affected by inflammation, phytates, or gut irritation. The body doesn’t have to fight it. It knows exactly what to do with it.

Bound vs unbound Iron

Iron is never meant to circulate freely. Inside the body, iron is always bound... to haemoglobin to carry oxygen, to ferritin for storage, and to transferrin for transport. These binding proteins are what make iron useful rather than destructive.

Problems arise when large amounts of unbound iron are introduced faster than the body can safely bind them.

Excess free iron is highly reactive. It drives oxidative stress, irritates tissue, and alters the intestinal environment. In the gut, unbound iron can disrupt the protective mucosal lining and feed iron-dependent pathogenic bacteria and parasites, shifting the microbiome away from balance. This helps explain why iron supplementation is so often associated with bloating, constipation, diarrhoea, abdominal discomfort, and worsening IBS-type symptoms.

The issue is not iron itself. It is iron divorced from its natural companions.

The forgotten role of copper

This is where the conversation usually stops, and where it should actually begin.

Iron cannot be properly utilised without copper.

Copper is required to:

• Mobilise stored iron from ferritin
• Load iron onto transferrin
• Incorporate iron into haemoglobin

Without copper, iron becomes trapped in storage. Ferritin may appear “normal” or even elevated, while tissues remain starved of oxygen.

This is known as functional iron deficiency, and it is increasingly common. Many people are told their iron levels are fine while symptoms persist. The missing piece is often copper.

Organ meats, particularly liver and spleen, provide iron and copper together in the ratios the human body evolved to use. Synthetic supplements almost never replicate this balance.

Why spinach won’t fix iron deficiency 

Spinach has had a reputation as an iron superfood for decades (in fact this is what I was told to eat more of by my doctor when I was iron deficient as a teenager). Technically, it contains iron. Practically, very little of it is absorbed.

The iron in spinach is non-heme and tightly bound to oxalates, compounds that significantly inhibit mineral absorption. Oxalates do not just block iron, they also interfere with calcium, magnesium, and zinc as well.

In sensitive individuals, high-oxalate diets can irritate the gut lining, increasing permeability and further impairing mineral uptake across the board. This does not make vegetables useless. It simply means they are not the blood builders they are sold to be.

The viscous cycle many women are trapped in

This is where iron deficiency becomes uniquely cruel to women.

Women lose iron through menstruation, that much is obvious. Blood loss equals iron loss. But what is far less discussed is what happens next, and why so many women find themselves trapped in a self-perpetuating loop.

Heavy periods deplete iron, yet iron deficiency itself can cause heavier periods. The deficiency deepens. And the next cycle becomes heavier still.

Once this cycle begins, it can be remarkably difficult to break.

Iron is not just a “blood mineral”. It plays a direct role in uterine function, vascular integrity, and muscular coordination. Adequate iron is required for the uterus to contract effectively during menstruation, compressing blood vessels, sealing capillaries, and limiting excessive blood loss. When iron levels are low, this process falters and the uterine muscles become weaker and less coordinated. Instead of firm, rhythmic contractions that efficiently shed the lining and close down bleeding, the uterus contracts sluggishly and inconsistently. Bleeding lasts longer. Flow becomes heavier. Clots are more common.

And unless iron status is restored alongside hormonal balance and metabolic support, this cycle continues month after month, quietly worsening, while the solution is repeatedly reduced to a single, insufficient instruction..."take more iron".