Iron: deficiency, symptoms, iron-rich foods and how to absorb it better

What iron does

Iron is a tiny mineral with an enormous job: it is part of haemoglobin, the protein in red blood cells that picks up oxygen in the lungs and delivers it around the body. Without enough iron, the blood carries less oxygen, and that is where the chain of deficiency symptoms begins: fatigue, breathlessness, paleness. But iron is not only in the blood; it also takes part in the muscles (in myoglobin), in energy production inside cells, and in the functioning of the immune system and the brain. That is why its lack shows up on so many fronts: it is not just "being more tired", it is that a basic cog of metabolism is running at half power. And since it is the most common deficiency in the world — affecting hundreds of millions of people — it is worth understanding well.

The symptoms of deficiency

Iron deficiency advances slowly, in stages: first the stores empty (ferritin drops) without symptoms, and only later, when there is not enough iron to make haemoglobin, does anaemia appear. The most common symptoms:

• Persistent fatigue and weakness, the most common sign.
• Paleness, especially in the face, the inside of the eyelids and the nails.
• Breathlessness or palpitations doing efforts that used to be easy.
• Headache, cold hands and feet, dizziness.
• Hair loss, brittle or spoon-shaped nails.
• Craving to chew ice or non-food substances (a curiously specific symptom).

Heme and non-heme iron: the key distinction

To understand dietary iron you have to separate two forms the body treats very differently. HEME iron comes from animal foods — red meat, fish, shellfish — and has a huge advantage: it is very well absorbed (15-35%) and is little affected by the rest of what you eat. NON-HEME iron comes from plants — legumes, leafy greens, nuts, wholegrains — and is absorbed much worse (2-20%), but with one big difference: its absorption is very modifiable depending on what accompanies it. This has a direct practical consequence: someone who eats meat rarely has to think about iron, while someone on a plant-based diet needs not only to eat enough iron but to learn to absorb it. The good news is that this absorption can be greatly improved, and that is what the next section is about.

Where iron is

The sources split into the two categories. Among animal ones (heme iron): organ meats like liver are the richest, followed by red meat, shellfish (clams, cockles, mussels) and, to a lesser extent, fish and poultry. Among plant ones (non-heme iron): legumes (lentils, chickpeas, beans, soy and tofu) are the base, along with dark leafy greens (spinach, chard), nuts and seeds (pistachios, pumpkin seeds, sesame) and wholegrain or fortified cereals. It is worth debunking the spinach myth: it does have iron, but non-heme and paired with oxalates that hinder its absorption, so it is not the superfood Popeye popularised. In total quantity, a well-planned plant-based diet covers iron amply; the challenge, again, is absorption.

How to absorb far more iron

Here is the most actionable part and the one that makes the biggest difference, especially for plant iron:

Who is most at risk

Iron deficiency is not spread evenly. The highest-risk groups are women of childbearing age, especially with heavy periods, because each cycle means an iron loss that must be replaced; pregnant women, whose needs soar; vegans and vegetarians, who rely on the worse-absorbed non-heme iron; endurance athletes, who lose iron through several routes and have higher needs; and people with digestive losses (ulcers, certain bowel diseases) or absorption problems. Recognising yourself in one of these groups does not mean you have a deficiency, but it does mean it is worth paying attention to dietary iron and, with symptoms, not hesitating to measure ferritin.

Measure before supplementing

We finish with the most important safety rule for iron, which sets it apart from other deficiencies: the excess is dangerous. Unlike water-soluble vitamins, the body has no efficient way to remove surplus iron, so taking supplements without a real deficiency can lead to toxic accumulation in organs such as the liver, on top of frequent digestive discomfort. That is why you should never supplement iron "just in case" or by self-diagnosis. The right approach, if you suspect it from symptoms or from belonging to a risk group, is a blood test: ferritin reflects the stores and the full blood count detects anaemia. If the test confirms deficiency, it will be your doctor who sets the dose, form and duration, and who monitors progress. For healthy everyday life, the tool is diet and absorption tricks, not pills.

Knowing whether you eat enough iron — and the well-absorbed kind — starts with knowing your real diet, and there Renzy makes it easy without counting by hand. By photographing your meals you see at a glance how many legumes, leafy greens, meat or fish really enter your week, and whether you pair plant iron with vitamin C or sabotage it with coffee. With that clear pattern you can adjust just what is needed — more sources, better combinations — and, if you are in a risk group, arrive at the appointment with concrete data instead of a vague impression. Iron is the perfect example that small combination changes count as much as eating more.