Iron

Iron is an essential mineral; adults contain about 3–4 g, most of it in hemoglobin that carries oxygen in blood. It is needed for red blood cell function, muscle oxygen use, energy metabolism, growth, and brain development. The two main dietary forms are heme iron from animal foods and nonheme iron from plant foods and fortified products. This matters because heme iron is generally absorbed more efficiently than nonheme iron, while nonheme absorption is more strongly affected by the rest of the meal.

What it is

Iron, also called Fe or dietary iron, is a trace mineral that the body must get from food or supplements. Most body iron is in hemoglobin inside red blood cells, with smaller amounts in myoglobin in muscle and in storage proteins such as ferritin. Iron is also part of many enzymes involved in energy production, DNA synthesis, and immune function.

A simple way to think about iron is that the body needs enough of it to deliver oxygen and support normal cell function, but not so much that excess iron builds up and causes harm. Both deficiency and overload can be serious.

Main forms of dietary iron

Form	Main sources	Typical absorption pattern
Heme iron	Meat, poultry, fish, seafood	Usually better absorbed
Nonheme iron	Pulses, beans, lentils, leafy greens, nuts, seeds, fortified cereals, supplements	Absorption varies more with meal composition

In India, iron nutrition is especially relevant because diets may be cereal-based and plant-forward, which can lower iron bioavailability even when total iron intake looks adequate. Fortified staples and public health programs are used in part to address this gap.

How it works

Iron's best-known role is in hemoglobin, the protein that carries oxygen from the lungs to tissues. It is also part of myoglobin, which helps muscles store and use oxygen. Beyond oxygen transport, iron supports mitochondrial energy production, neurological development, connective tissue function, and the synthesis of some hormones and signaling molecules.

The body tightly regulates iron absorption because it has no active way to excrete large amounts of iron. Most absorption happens in the small intestine. A liver-produced hormone called hepcidin is a key regulator: when iron stores are high or inflammation is present, hepcidin rises and reduces iron absorption; when stores are low, hepcidin falls and absorption increases.

Iron absorption depends on the form eaten and what is consumed with it:

1. Vitamin C can improve nonheme iron absorption by helping keep iron in a more absorbable form.
2. Meat, fish, and poultry can enhance nonheme iron absorption from the same meal.
3. Phytates in whole grains, legumes, and some seeds can reduce absorption.
4. Polyphenols in tea and coffee can reduce absorption, especially when taken with meals.
5. Calcium may modestly inhibit absorption in some settings.

Food preparation can matter. Soaking, fermenting, sprouting, and using vitamin C-rich foods such as amla, guava, citrus, or tomatoes with meals may improve nonheme iron absorption.

Evidence and uses

Iron is used to prevent or treat iron deficiency and iron-deficiency anemia. It is especially important during infancy, adolescence, pregnancy, and in people with blood loss, low dietary intake, malabsorption, or chronic kidney disease.

Common food sources include red meat, poultry, fish, shellfish, lentils, chickpeas, rajma, soy foods, dark green leafy vegetables, jaggery-containing mixed foods, and iron-fortified cereals or flours. Food alone may be enough for prevention in many people, but established deficiency often needs supplements and evaluation for the cause.

Selected intake reference points from NIH ODS

Group	Recommended dietary allowance
Adult men 19+ years	8 mg/day
Women 19–50 years	18 mg/day
Pregnancy	27 mg/day
Women 51+ years	8 mg/day

These are general reference values, not treatment doses. In India, pregnancy and adolescent health programs often include iron-folic acid supplementation because deficiency is common at the population level.

Evidence strongly supports iron treatment when deficiency is confirmed. Benefits can include improved hemoglobin, replenished iron stores, and reduced fatigue related to deficiency. But iron is not a general energy booster for everyone. If fatigue has another cause, taking iron may not help and can be unsafe.

Evidence is more mixed for routine supplementation in people without deficiency. Some groups at higher risk may benefit from screening or preventive supplementation under public health guidance, but unnecessary iron use should be avoided.

Safety and interactions

Iron supplements commonly cause nausea, abdominal discomfort, constipation, diarrhea, dark stools, and sometimes vomiting. Taking iron with food can reduce stomach upset, but food may also reduce absorption. Different iron salts and dosing schedules can affect tolerability.

Keep iron supplements out of reach of children. Accidental overdose can be a medical emergency, especially in young children.

Important interactions

Interacting item	What can happen
Levothyroxine	Iron can reduce absorption; doses usually need separation
Tetracycline and quinolone antibiotics	Iron can reduce antibiotic absorption
Bisphosphonates	Iron may interfere with absorption
Antacids, proton pump inhibitors	Can reduce iron absorption
Calcium supplements	May reduce iron absorption if taken together

People with hemochromatosis, repeated blood transfusions, some liver diseases, or unexplained high ferritin should not start iron on their own. Talk to a clinician or pharmacist before using supplements, especially during pregnancy, in children, or if you take regular medicines.

When to see a clinician

See a clinician if you have symptoms that could suggest iron deficiency or anemia, such as unusual fatigue, shortness of breath on exertion, dizziness, headaches, paleness, brittle nails, pica, or restless legs. Also seek care if you have heavy menstrual bleeding, blood in stool, black stools not explained by iron tablets, chronic digestive symptoms, or a history of ulcers or bowel disease.

A clinician may order tests such as hemoglobin, ferritin, transferrin saturation, and sometimes C-reactive protein because inflammation can affect ferritin interpretation. In adults, especially men and postmenopausal women, iron deficiency often needs a search for the cause rather than treatment alone.

Limitations and open questions

Iron biology is complex. A normal or high ferritin does not always rule out functional iron deficiency because ferritin can rise with inflammation, infection, liver disease, or obesity. This is one reason iron status is not judged by a single number in every case.

There is also ongoing debate about the best supplement form, dose frequency, and how to balance efficacy with side effects. Evidence in humans supports iron treatment for deficiency, but the ideal approach can differ by age, pregnancy status, inflammation, kidney disease, and diet pattern. Research continues on better biomarkers, food fortification strategies, and ways to improve iron absorption from plant-based diets without increasing risk from excess iron.