Iron

Iron occurs in food in two forms, which the body absorbs quite differently. Haem iron — from meat and fish — is absorbed efficiently and relatively independently of the rest of the meal. Non-haem iron, present in plant foods, is absorbed considerably less well, and its absorption also depends strongly on what we eat alongside it.

What helps and what hinders

Absorption of non-haem iron is increased by vitamin C present in the same meal. Working in the opposite direction are tannins from tea and coffee and phytates from grains and legume seeds — which is why washing a meal down with strong tea is one of the more commonly cited everyday habits that limit iron absorption. Soaking, sprouting and souring seeds partly breaks down phytates.

This difference in bioavailability is directly reflected in reference values: some organisations give higher values for people on a plant-based diet than for others, precisely because they assume poorer absorption.

Why this isn't a nutrient to supplement “just in case”

The body has no effective mechanism for excreting excess iron — it regulates its level mainly at the absorption stage. This is why iron is one of the nutrients for which supplementing on your own without a confirmed deficiency is a bad idea, and in people with haemochromatosis or other iron-metabolism disorders it can even be harmful.

Iron deficiency is diagnosed with blood tests — ferritin, full blood count, iron-status markers — not on the basis of how you feel or by comparing your diet with a reference table. If you suspect a deficiency, that's a conversation with a doctor and a request for tests, not a decision made at the pharmacy.