Why Do We Need Iron?

Iron is the most common nutritional deficiency on the planet, and most of us barely think about it. In this episode, Jen, Chris and Matt unpack why iron quietly runs every cell in your body, why so many of us are running short, and why the tiredness it causes is the kind no amount of coffee will fix. Around a quarter of the world is anaemic, and iron deficiency is behind roughly half of those cases. Yet iron rarely gets the attention of magnesium or vitamin D. The team explains what iron actually does, why a standard blood test can miss a deficiency entirely, the difference between plant and animal iron, who needs far more than the average, and the simple, manageable habits that keep iron levels healthy whatever your diet. In this episode: The most common deficiency you've never heard of (00:48) Iron deficiency without anaemia, and why tests miss it (03:08) What iron actually does in the body (05:12) Heme vs non-heme iron and what affects absorption (08:23) Who needs more iron (11:50) Food sources, testing and supplements (16:45) Iron Is the Oxygen Courier Service Your Body Can't Run Without Around 70% of the iron in your body is locked inside two proteins, haemoglobin in your red blood cells and myoglobin in your muscles, and both exist to move oxygen around. Each haemoglobin molecule carries four iron atoms, each grabbing a single oxygen molecule in the lungs and releasing it where it's needed. (05:12) When iron drops, your body makes smaller red blood cells with less haemoglobin, so each one carries less oxygen The delivery never stops, it just sends half-empty parcels That single shortage is why symptoms feel so scattered, from brain fog to breathlessness to brittle nails "Iron's basically the postmaster in the postal system. Without it, the oxygen never gets sorted, never gets delivered, and never makes it to the front door." — Matt Why a Normal Blood Test Can Still Miss Low Iron There's a category called iron deficiency without anaemia, where your stores are depleted and you feel rough, but your haemoglobin hasn't fallen far enough to trigger an anaemia diagnosis. The standard test measures haemoglobin, which is the last thing to fall. (03:08) Ferritin, your iron storage marker, is the true early warning sign It often isn't checked unless a doctor specifically asks for it This is why persistent fatigue gets blamed on being busy or sleeping badly "The true early warning sign is ferritin, which is your iron storage marker, and unless your doctor specifically asks for it, it often doesn't get checked." — Chris Plant Iron and Animal Iron Behave Very Differently Heme iron from meat, fish and shellfish absorbs at roughly 15 to 35%, almost regardless of the meal. Non-heme iron from plants, eggs and fortified foods absorbs far lower, from 2 to 20%, and is heavily affected by what's around it. (08:23) Phytates in whole grains, nuts and legumes can cut absorption by over 50% Tea, coffee, calcium and some proteins reduce it further Vitamin C is a standout enhancer, so a squeeze of lemon or a glass of orange juice genuinely helps Who Actually Needs More Iron This is a nutrient where the average barely means anything. An adult man under 50 needs around 8 milligrams a day, a woman of reproductive age about 18, and a pregnant woman about 27, more than a threefold difference. (11:50) Pregnancy is the most demanding window, with around one gram of iron needed across the whole pregnancy Female athletes, people on plant-based diets and infants aged six months to two years all carry extra demand For most people, iron is very manageable with a little awareness "People often describe it as the lights coming back on, because every system that depends on oxygen delivery suddenly has the resources it needs again." — Jen About So That's Why So That's Why is a weekly podcast where Jen, Chris, and Matt unpack the science behind everyday health questions. No jargon, no judgment, just genuine curiosity and proper research.