Dietary Iron: Nutrient Overview, Benefits, and More

Iron is an essential mineral that your body needs to function properly. Without enough iron, you can’t make enough healthy red blood cells.

Most people know iron is important, but many don’t understand exactly what it does or how much they need.

In this article, we’ll explain dietary iron’s functions, best food sources, and how to prevent deficiency.

What Is Dietary Iron?

Iron is a mineral that your body needs to make hemoglobin. Hemoglobin is a protein in red blood cells that carries oxygen from your lungs to the rest of your body.

Your body uses iron for many other important functions, too. It helps produce certain hormones (1) and supports your immune system (2).

Heme Iron vs. Non-Heme Iron

There are two main types of iron in food. Each type is absorbed differently by your body.

Heme Iron

Heme iron comes from animal sources. Your body absorbs it more easily than non-heme iron (3).

You’ll find heme iron in red meat, poultry, and fish. It makes up about half of the iron in meat (4).

Non-Heme Iron

Non-heme iron comes from plant sources. Your body doesn’t absorb it as well as heme iron.

Plant foods like beans, spinach, and fortified cereals contain non-heme iron. It makes up all the iron in plants and about half of the iron in meat.

Benefits of Dietary Iron

Iron performs several vital functions in your body. Without enough iron, these processes can’t work properly.

Oxygen Transport

The most important job of iron is helping transport oxygen throughout your body. Iron is a key part of hemoglobin, which binds to oxygen in your lungs. Research shows that oral iron treatment can improve cardiac function by increasing oxygen delivery to tissues (5).

Energy Production

Iron helps your cells produce energy. It’s part of the vital enzymes for ATP synthesis (6). Studies show that iron supplementation can reduce fatigue by 47.7% in women with low iron levels (7).

Brain Function

Your brain needs iron to function properly. Iron is a cofactor for enzymes that produce neurotransmitters like dopamine and serotonin (8). Children with ADHD have significantly lower serum ferritin levels compared to healthy children (8).

Immune Function

Iron supports your immune system by helping your body fight infections. Iron deficiency impairs both cell-mediated and innate immunity (9).

Signs and Symptoms of Iron Deficiency

Iron deficiency is the most common nutritional deficiency worldwide (10). It can develop slowly, so symptoms may not be obvious at first.

Common Symptoms

The most common signs of iron deficiency include extreme tiredness and pale skin. Pallor is the most frequent presenting feature (10).

• Extreme tiredness and weakness
• Pale skin and pale coloring inside the lower eyelids
• Shortness of breath
• Dizziness or lightheadedness
• Cold hands and feet
• Brittle nails (koilonychia) (11)
• Frequent infections
• Unusual cravings for non-food items (pica) (12)

Research shows that iron deficiency without anemia can still cause significant fatigue (7).

Who’s at Risk

Certain groups are more likely to develop iron deficiency. Women with heavy menstrual bleeding face a higher risk (13).

• Women of childbearing age: Monthly periods increase iron loss
• Pregnant women: Iron needs increase significantly during pregnancy
• Young children: Rapid growth requires more iron
• Vegetarians and vegans: Plant-based iron is harder to absorb
• People with celiac disease: About 1 in 31 patients with iron deficiency anemia have celiac disease (14)

Studies show that iron-biofortified crops can improve cognitive performance in attention and memory domains in children (15).

How Much Iron Do You Need?

Your iron needs depend on your age, sex, and life stage. The body can’t make iron, so you must get it from food or supplements.

Daily Iron Requirements

The official Recommended Dietary Allowance (RDA) for adult men is 8 mg per day. The RDA for women ages 19-50 is 18 mg per day (16).

• Adult men: 8 mg per day
• Women ages 19-50: 18 mg per day
• Women over 50: 8 mg per day
• Pregnant women: 27 mg per day
• Breastfeeding women: 9 mg per day

Research found that the median iron requirement for women aged 18-29 is about 7.6 mg per day (17).

Best Food Sources of Iron

You can get iron from both animal and plant foods. Different foods contain different amounts and types of iron.

Heme Iron Sources

Heme iron from animal products is absorbed 2-3 times better than non-heme iron. Red meat provides the most heme iron.

• Red meat: Beef, lamb, and venison
• Poultry: Chicken and turkey
• Fish and seafood: Tuna, salmon, oysters, and clams
• Organ meats: Liver and kidney

Non-Heme Iron Sources

Plant-based foods contain non-heme iron. While it’s not absorbed as well, these foods are still important iron sources.

• Legumes: Lentils, chickpeas, beans, and peas
• Nuts and seeds: Pumpkin seeds, cashews, and pistachios
• Whole grains: Quinoa, oatmeal, and fortified cereals
• Dark leafy greens: Spinach, kale, and Swiss chard
• Dried fruit: Apricots, raisins, and prunes

Research shows that whole grain products maintain more iron than refined grains (19).

Iron-Fortified Foods

Many foods are fortified with iron to help prevent deficiency. Breakfast cereals and bread are commonly fortified.

• Breakfast cereals
• Infant formulas
• Bread and pasta
• Rice and other grains

Studies show that flour fortification programs can reduce iron deficiency in women (20).

How to Improve Iron Absorption

Your body’s ability to absorb iron depends on several factors. You can increase absorption by combining iron-rich foods with certain nutrients.

Iron Absorption Enhancers

Some foods and nutrients help your body absorb more iron. Vitamin C is the most powerful enhancer.

• Vitamin C: Found in citrus fruits, tomatoes, and bell peppers
• Meat proteins: Help absorb non-heme iron from plants
• Fermented foods: May improve iron availability

Vitamin C can overcome the inhibitory effect of calcium on iron absorption (21). One study found that ascorbic acid nearly doubled iron absorption from fortified milk (22).

Iron Absorption Inhibitors

Some foods and substances can reduce iron absorption. Calcium is one of the strongest inhibitors.

• Calcium: Found in dairy products
• Tannins: In tea and coffee
• Phytates: In whole grains and legumes
• Polyphenols: In some vegetables and tea

Research shows that 500 mg of calcium reduced iron absorption from 10.2% to 4.8% in women (23).

Iron Supplements

Sometimes diet alone isn’t enough to meet your iron needs. Supplements can help fill the gap.

Types of Iron Supplements

There are several forms of iron supplements available. Ferrous sulfate is the most common and well-absorbed.

• Ferrous sulfate: Most common, but can cause GI side effects (24)
• Ferrous gluconate: Has similar GI side effects to ferrous sulfate (25)
• Ferric citrate: Often used in medical settings
• Iron polysaccharide: May cause fewer side effects

Studies show that ferrous iron has better bioavailability than ferric iron preparations (26).

Who Might Need Supplements

Iron supplements may be recommended for people with a diagnosed deficiency. Pregnant women often need supplements too.

• People diagnosed with iron deficiency anemia
• Pregnant women
• Heavy menstrual bleeding
• Frequent blood donors
• People with certain digestive disorders

High-dose intravenous iron improves hemoglobin faster than oral iron in severe deficiency (27).

Taking Iron Supplements Safely

If you take iron supplements, follow these guidelines for best results. Take them on an empty stomach when possible.

• Take on an empty stomach for best absorption
• If stomach upset occurs, take it with a small amount of food
• Don’t take with calcium supplements or antacids
• Store safely away from children

Studies show no significant advantage in taking iron more than once daily (28).

Iron and Special Populations

Different groups have unique iron needs and considerations. Pregnant women and athletes need extra attention to iron intake.

Iron During Pregnancy

Pregnancy dramatically increases iron needs. The developing baby and placenta require extra iron. Daily iron supplementation during pregnancy reduces the risk of low birthweight babies (29). Intermittent iron during pregnancy causes fewer side effects than daily doses (30).

Iron for Athletes

Athletes, especially female athletes, have higher iron needs. About 30% of female athletes experience iron deficiency (31). Synbiotic supplements with iron improve iron status in female athletes (31).

Iron for Vegetarians

Vegetarians have significantly lower serum ferritin levels than non-vegetarians (32). The Institute of Medicine recommends vegetarians consume 1.8 times more iron than meat eaters (33). A green Mediterranean diet with plant supplements doesn’t impair iron homeostasis (34).

Health Conditions Related to Iron

Both too little and too much iron can cause health problems. The balance is important for good health.

Iron Deficiency Anemia

This is the most severe form of iron deficiency. It occurs when your body doesn’t have enough iron to make hemoglobin. Oral iron raises hemoglobin in elderly people by 0.35 g/dL after 4-6 weeks (35).

Iron and Heart Disease

The relationship between iron and heart disease is complex. Research shows mixed effects on different conditions. Higher iron biomarkers were protective for coronary artery disease but increased diabetes risk (36). Intravenous iron significantly improves symptoms in heart failure patients with iron deficiency (37).

Iron Overload

Too much iron can be harmful. Conditions like hemochromatosis cause the body to absorb too much iron. Genetic variants affect iron metabolism and deficiency risk (38).

Testing Your Iron Levels

If you suspect iron deficiency, your doctor can order blood tests. Several tests can measure your iron status accurately.

Common Iron Tests

Several tests can measure your iron levels. Each test provides different information about your iron status.

• Ferritin: Shows iron stores in your body
• Hemoglobin: Measures oxygen-carrying capacity
• Transferrin saturation: Shows how much iron is being transported
• Total iron-binding capacity: Indicates iron transport capacity

Research shows iron status tests are seldom prescribed despite recommendations (39).

Normal iron levels vary by age and sex. Different reference intervals are used for men and women (40).

The Bottom Line

Iron is essential for carrying oxygen throughout your body and producing energy. Most people can get enough iron from a balanced diet.

If you’re at risk for deficiency, focus on iron-rich foods and pair them with vitamin C. When diet isn’t enough, supplements can help.

Work with your healthcare provider to determine the best approach for your needs. Regular testing can help monitor your iron status over time.