Iron: Absorption, Deficiency, and Appropriate Intake

Takeaways

• Iron transports oxygen throughout your body
• Both plant and animal foods contain iron
• Vitamin C boosts iron absorption
• Iron deficiency can cause fatigue and weakness
• Too much iron can be harmful
• Consult a doctor before taking iron supplements

What is Iron?

Iron is a vital mineral for your body’s proper function.[1] It plays a key role in hemoglobin, a protein within red blood cells. Hemoglobin’s main task is to carry oxygen from your lungs to all parts of your body.[2]

Your body cannot produce iron on its own, so you must obtain it through your diet or supplements.[3] Iron exists in two forms: heme and non-heme.[4] Heme iron is found in animal-based foods, while non-heme iron is found in plant-based foods and iron-fortified products.

The majority of iron in your body is located in your red blood cells.[5] However, all cells contain some iron. Your body also stores extra iron in organs such as your liver, spleen, and bone marrow.[6]

Iron’s Functions in the Body

Oxygen Transport

Iron’s primary function is to aid in the transport of oxygen throughout your bloodstream.[7] It achieves this as part of hemoglobin in red blood cells. When you inhale, oxygen attaches to the iron within hemoglobin, and your blood then carries this oxygen-rich hemoglobin to all of your tissues.[8]

If you don’t have enough iron, your body can’t create enough healthy red blood cells, leading to anemia.[9] People with anemia often experience tiredness and weakness because their bodies aren’t receiving enough oxygen.[10]

Energy Production

Iron also plays a role in energy production.[11] It’s a component of several enzymes involved in this process. These enzymes break down nutrients from food and convert them into energy that your cells can use.

Iron is essential for your muscles, helping them to both store and use oxygen.[12] This is why an iron deficiency can cause weakness and fatigue; your muscles are not getting the necessary oxygen to function properly.

Iron Absorption

Factors Affecting Absorption

Your body doesn’t absorb all the iron you consume. Several factors influence how much iron your body actually takes in. Understanding these factors can help you increase your iron intake through your diet.

Factors that increase iron absorption include:

• Vitamin C
• Animal protein
• Acidic foods

Vitamin C significantly enhances iron absorption.[13] It helps change iron into a form that your body can absorb more easily. Consuming vitamin C-rich foods along with iron-rich foods can improve iron absorption.

Animal protein also aids in iron absorption.[14] This is one reason why heme iron, which comes from animal sources, is more readily absorbed than non-heme iron.

Acidic foods can also help increase iron absorption.[15] Foods like citrus fruits, which are also high in Vitamin C, have this effect.

Inhibitors of Iron Absorption

Some substances can hinder your body’s ability to absorb iron; these are known as inhibitors. Knowing about these can help you plan your meals more effectively.

Common inhibitors of iron absorption include:

• Calcium
• Tannins (in tea and coffee)
• Phytates (in whole grains and legumes)
• Polyphenols (in some fruits and vegetables)

Calcium can interfere with the absorption of both heme and non-heme iron.[16] It’s not necessary to avoid calcium entirely, but try to avoid eating high-calcium and high-iron foods at the same time.

Tannins, found in tea and coffee, can greatly reduce iron absorption.[17] If you consume these beverages with your meals, you might absorb less iron from your food.

Phytates found in whole grains and legumes can also lower iron absorption.[18] Soaking or sprouting these foods before cooking can help reduce their phytate content.

Dietary Sources of Iron

Heme Iron Sources

Heme iron comes from animal products.[19] Your body absorbs it more easily compared to non-heme iron.[20] About 15-35% of heme iron is absorbed[21] , making it a beneficial option if you need to increase your iron intake.

Foods rich in heme iron include:

• Red meat
• Poultry
• Fish
• Organ meats (like liver)

Red meat is a primary source of heme iron.[22] A 3-ounce portion of beef can provide about 3 milligrams of iron, which is about 15-20% of the daily recommended amount for many adults.

Poultry and fish also provide heme iron, although usually less than red meat.[23] Dark meat poultry contains more iron than white meat.

Organ meats, especially liver, have very high iron levels, but they are also high in cholesterol. It’s best to consume them in moderation.

Non-Heme Iron Sources

Non-heme iron is found in plant-based foods and iron-fortified products.[24] Your body does not absorb it as readily as heme iron.[25] Only about 2-20% of non-heme iron is absorbed[26] , but this can be improved by consuming these foods with Vitamin C or meat.

Plant-based and other non-heme iron sources include:

• Legumes (beans, lentils, chickpeas)
• Tofu
• Spinach and other dark leafy greens
• Dried fruits (raisins, apricots)
• Iron-fortified cereals and breads

Legumes are a good source of iron.[27] A cup of cooked lentils provides about 6.6 milligrams of iron, or approximately 37% of the daily recommended amount for many adults.

Spinach and other dark leafy greens also contain iron.[28] Cooking these greens helps make the iron more accessible for absorption. A half-cup of cooked spinach provides about 3.2 milligrams of iron.

Many breakfast cereals are fortified with iron.[29] Some can provide 100% of your daily iron needs in a single serving. Check the nutrition label to see the specific iron content of a product.

Iron Deficiency

Causes of Iron Deficiency

Iron deficiency is the most common nutritional deficiency globally.[30] It occurs when your body doesn’t have enough iron to produce healthy red blood cells, which can lead to iron deficiency anemia.

Common reasons for iron deficiency include:

• Inadequate dietary intake
• Poor absorption
• Blood loss
• Increased iron needs

Not consuming enough iron-rich foods is a primary cause of deficiency.[31] This is particularly true for vegetarians and vegans, as plant-based diets only contain non-heme iron, which is more difficult to absorb.

Certain health conditions can interfere with iron absorption, such as celiac disease and inflammatory bowel diseases.[32] If you have these conditions, you may develop an iron deficiency even if you eat enough iron.

Blood loss can cause iron deficiency.[33] Women who experience heavy periods are at a higher risk. Internal bleeding, from sources like ulcers or colon cancer, can also lead to iron deficiency.

Certain life stages increase your iron needs, including pregnancy, breastfeeding, and periods of rapid growth in childhood and adolescence.[34] If you don’t increase your iron intake during these times, you may become deficient.

Symptoms of Iron Deficiency

Iron deficiency develops over time, so you may not notice symptoms until it becomes severe. Recognizing the early signs can help you address the issue more quickly.

Progression of iron deficiency symptoms:

1. Mild fatigue and weakness
2. Pale skin and fingernails
3. Shortness of breath during exercise
4. Headaches and dizziness
5. Unusual cravings for non-food items (pica)

Fatigue is often the first symptom of iron deficiency.[35] You might feel tired even after a full night’s sleep, because your body is not getting enough oxygen.

As iron deficiency progresses, your skin may become pale, especially in the insides of your eyelids, gums, and nails.[36] Your nails may also become brittle or have a spoon-like shape.

You might experience shortness of breath easily, particularly during physical activity.[37] This is because your body struggles to transport oxygen efficiently.

Headaches and dizziness can occur as iron deficiency becomes more severe due to reduced oxygen flow to the brain.[38]

Some individuals with iron deficiency develop unusual cravings. They may want to eat dirt, ice, or other non-food items, a condition known as pica.[39]

Diagnosis and Testing

If you suspect that you might be iron deficient, it’s important to consult your doctor. They can perform blood tests to check your iron levels, and diagnose iron deficiency before it leads to anemia.

Common blood tests to check iron levels include:

• Hemoglobin
• Ferritin
• Transferrin saturation
• Total iron-binding capacity (TIBC)

Hemoglobin measures the iron-containing protein in your red blood cells.[40] Low hemoglobin levels can be an indicator of iron deficiency anemia.

Ferritin shows how much iron your body has stored.[41] It’s often the first test to show abnormalities in cases of iron deficiency. A low ferritin level usually indicates that you are iron deficient.

Transferrin saturation measures how much of your blood’s iron-carrying capacity is being used.[42] A low percentage can be an indicator of iron deficiency.

TIBC measures your blood’s capacity to bind transferrin with iron.[43] High levels can indicate iron deficiency.

Your doctor will evaluate these results collectively, also considering your symptoms and risk factors, to make an accurate diagnosis.

Iron Supplementation

Types of Iron Supplements

If you are diagnosed with iron deficiency, your doctor may recommend iron supplements. These supplements come in various forms, each with its own advantages and disadvantages.

Different types of iron supplements include:

• Ferrous sulfate
• Ferrous gluconate
• Ferrous fumarate
• Iron amino acid chelates

Ferrous sulfate is the most common type; it’s affordable and easily available.[44] However, it can cause stomach upset in some individuals.

Ferrous gluconate is generally gentler on the stomach, but contains less elemental iron than ferrous sulfate[45] , meaning you might need to take more to get the same amount of iron.

Ferrous fumarate contains the highest amount of elemental iron and is often used to treat severe iron deficiency.[46] It also has a higher chance of causing side effects.

Iron amino acid chelates are easier for your body to absorb and tend to cause fewer side effects.[47] However, they are usually more expensive than other forms.

Dosage and Timing

The proper dosage of iron depends on your age, sex, and iron status. Always follow your doctor’s recommendations, as taking too much iron can be harmful.

Most adults with iron deficiency require 60-120 mg of elemental iron per day, usually divided into 2-3 doses.[48] Treatment generally lasts 3-6 months.

Take iron supplements on an empty stomach if possible, as this improves absorption.[49] If they upset your stomach, you can take them with food, but avoid calcium-rich foods or drinks.

To increase absorption, take iron with Vitamin C[50] , which can be from a supplement or from a glass of orange juice taken with your iron pill.

Potential side effects of iron supplements include:

• Constipation
• Nausea
• Stomach pain
• Dark stools

These side effects are usually mild and often improve over time. If they persist or bother you, talk to your doctor. They may suggest changing your dosage or the type of supplement.

Iron Overload

Causes of Iron Overload

While iron deficiency is common, some people have the opposite problem of absorbing too much iron. This leads to a condition known as iron overload, or hemochromatosis.

Iron overload can occur due to several reasons:

• Hereditary hemochromatosis
• Frequent blood transfusions
• Excessive iron supplementation
• Certain liver diseases

Hereditary hemochromatosis is a common cause of iron overload.[51] It’s a genetic condition that causes your body to absorb too much iron from food. This excess iron then builds up in your organs over time.

People who receive frequent blood transfusions can also develop iron overload.[52] Each unit of blood contains iron, and over time, this iron can accumulate in the body.

Taking excessive amounts of iron supplements can lead to iron overload, which is why you should only take iron supplements under medical supervision.[53]

Some liver diseases can also cause iron to build up in the body, including conditions like chronic hepatitis C and alcoholic liver disease.[54]

Risks and Complications

Iron overload can damage many organs in your body, as iron builds up in the tissues over time, which can lead to serious health issues.

Organs and systems affected by excess iron include:

• Liver
• Heart
• Pancreas
• Joints
• Endocrine glands

The liver is frequently the first organ affected by iron overload.[55] Excessive iron can cause liver enlargement, cirrhosis, and potentially liver cancer.

Iron overload can damage your heart muscle, potentially leading to heart failure or irregular heart rhythms.[56]

Excess iron in the pancreas can result in diabetes by damaging the cells that produce insulin.[57]

Some individuals with iron overload experience joint pain and arthritis, although the exact cause is not entirely understood, it may involve iron deposits in the joints.

Iron overload can affect your endocrine glands, potentially leading to problems such as hypothyroidism or hypogonadism.

If left untreated, iron overload can be life-threatening. Early diagnosis and treatment are important. Treatment often involves the regular removal of blood to lower iron levels.

Special Considerations

Pregnancy and Iron Needs

Pregnancy increases the need for iron as your body uses it to produce extra blood for the baby. The baby also stores iron for use after birth.

During pregnancy, your iron needs almost double.[58] Most pregnant women require 27 mg of iron daily[59] , which can be difficult to obtain from diet alone. Many doctors recommend iron supplements during pregnancy.

Not getting enough iron during pregnancy can lead to anemia, which increases the risk of:

• Premature birth
• Low birth weight
• Postpartum depression

Your doctor will monitor your iron levels during prenatal visits. If you are anemic, they may recommend higher doses of iron.

Some pregnant women may experience nausea when taking iron supplements. If this occurs, talk to your doctor, who may suggest taking iron with food or changing the type of supplement.

Athletes and Iron Status

Athletes, particularly those who engage in endurance sports, have increased iron needs due to several factors:

• Increased red blood cell production
• Iron loss through sweat
• Gastrointestinal blood loss

Intense exercise stimulates red blood cell production, which uses up more iron.[60] Some athletes also lose iron through sweat[61] , while endurance athletes may experience small amounts of gastrointestinal bleeding during prolonged events.

Female athletes face a greater chance of iron deficiency due to menstrual blood loss.[62] Athletes who follow a vegetarian diet also need to be especially mindful of consuming enough iron.

Common signs of iron deficiency in athletes can include feeling tired, weakness, and decreased athletic performance.

• Decreased performance
• Increased fatigue
• Slower recovery times

If you are an athlete, it’s a good idea to get your iron levels checked regularly. Make sure to eat foods with iron, and consider iron supplements only if your doctor advises it.

Vegetarian and Vegan Diets

Plant-based diets can provide sufficient iron, but require careful planning to ensure you are consuming enough. Individuals who are vegetarians or vegans have a higher risk of iron deficiency.

Plant-based foods contain non-heme iron, which your body doesn’t absorb as well as heme iron from animal products. Because of this, vegetarians and vegans may need to consume about 1.8 times more iron than people who eat meat.

There are several strategies you can use to maximize your iron intake on a plant-based diet.

• Eat iron-rich plant foods daily
• Combine iron-rich foods with vitamin C
• Use cast-iron cookware
• Consider fortified foods

Good plant-based sources of iron include foods like legumes, tofu, nuts, seeds, and dark leafy greens. Try to incorporate these into your diet regularly.

Vitamin C can significantly improve your body’s absorption of non-heme iron. Consuming foods rich in Vitamin C alongside iron-rich foods is a good idea. For instance, add some lemon juice to your spinach salad.

Cooking with cast iron cookware can increase the iron content of your food, especially for foods that are acidic like tomato sauce.

Many breakfast cereals and plant-based milk alternatives have added iron. These can be helpful ways to get more iron, especially if you have difficulty meeting your needs through whole foods alone.

If you eat a plant-based diet, consider getting your iron levels checked regularly. If your iron levels are low, your doctor might recommend you take a supplement.

FAQs

Conclusion

Iron is a crucial mineral for your health. Your body needs iron to carry oxygen, produce energy, and for other important processes. Although iron deficiency is common, it can be prevented and treated.

A balanced diet will usually provide enough iron for most people. Make sure your meals include a variety of foods that contain iron. If you are at risk of iron deficiency, you need to be extra mindful of your intake. This includes pregnant women, menstruating women, athletes, and those who follow plant-based diets.

When it comes to iron, remember that more is not always better. Consuming too much iron can be harmful. Only take iron supplements if recommended by your doctor. They will determine if you need them, and what dosage is right for you.

If you are concerned about your iron levels, talk to your doctor. They can test your iron levels and offer specific advice. By taking the correct steps, you can maintain healthy iron levels and help your overall health.

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