Definition of iron deficiency

It is important to distinguish between iron deficiency and anemia. Iron deficiency is characterized by the depletion of the body's iron stores, without indicating the degree of depletion or the presence of anemia. An individual can have iron deficiency without being anemic. However, iron deficiency remains a common cause of anemia, a condition where the body's iron stores are very low. Iron deficiency is also one of the most common deficiencies worldwide.

Etiology of iron deficiency

In adults, iron deficiency is generally due to blood loss, such as heavy menstrual bleeding or hemorrhage in the digestive tract. It can also be caused by certain digestive diseases that lead to malabsorption, such as celiac disease. Finally, iron deficiency can also be due to inadequate diet, especially in children and pregnant women who have increased iron needs.

Symptoms of iron deficiency

When the body's iron stores are severely depleted, anemia due to iron deficiency, also called iron-deficiency anemia, occurs. Symptoms of anemia may include fatigue, weakness, paleness, difficulty concentrating and learning. Severe anemia can also cause an increased heart rate, dizziness, difficulty breathing, and absence of menstruation.

Diagnosis of iron deficiency

The diagnosis of iron deficiency is generally made based on the symptoms present and blood test results. At diagnosis, it is also important to differentiate anemia due to iron deficiency from other types of anemia. Anemia due to iron deficiency is characterized by abnormally small and pale red blood cells.

Treatment of iron deficiency

When iron deficiency is caused by bleeding, treatment involves controlling the bleeding. Treatment may also include taking medications, dietary supplements, and rarely intravenous iron administration. When iron deficiency is due to inadequate dietary intake, taking an iron supplement and making nutritional changes can help treat it.

Nutritional approach to iron deficiency

The nutritional approach generally includes increasing the consumption of iron-rich foods. A healthcare professional may also prescribe an iron supplement.

Iron in the diet

Iron is a mineral naturally found in many foods. There are two types of iron: heme iron and non-heme iron. Heme iron is found in animal-based foods such as meat, fish, and seafood. Non-heme iron is mainly present in plant-based foods, such as legumes, nuts, seeds, enriched grains (e.g., pasta), soy products (e.g., tofu, tempeh, fortified soy beverages), and certain vegetables (e.g., dark leafy greens). Heme iron is better absorbed by the body than non-heme iron, which accounts for about 85% of iron intake in an average diet.

Substances that limit the absorption of non-heme iron

Certain substances present in foods interfere with the absorption of non-heme iron. These substances bind to non-heme iron and prevent its absorption. This is notably the case with phytates found in legumes, whole grains, and nuts, calcium present in milk, as well as certain polyphenols found in tea and coffee. For people with iron deficiency, it is therefore preferable to consume tea or coffee at least 30 minutes before or after meals containing a source of non-heme iron.

Increasing the absorption of non-heme iron

There are two ways to increase the absorption of non-heme iron by the body. The first is to combine a source of non-heme iron with a source of vitamin C, which is mainly found in vegetables and fruits. For example, spinach can be drizzled with a splash of lemon juice or a pasta salad served with tomatoes. The second way to increase the absorption of non-heme iron is to combine it with animal protein. For example, red beans and ground meat can be combined in chili.

Daily iron requirements for adults

Sources of heme iron

Heme iron is found in animal-based foods such as:

• Meat (e.g., beef, pork, lamb)
• Poultry (e.g., chicken, turkey)
• Fish (e.g., trout, tuna, sardines)
• Seafood (e.g., shrimp, scallops, mussels, oysters)
• Organ meats (e.g., liver, kidneys)

Sources of non-heme iron

Non-heme iron is mainly found in plant-based foods such as:

• Legumes (e.g., green lentils, chickpeas, white beans)
• Nuts and nut butters (e.g., peanuts, almonds, pistachios)
• Seeds and seed butters (e.g., pumpkin, sunflower)
• Certain vegetables (e.g., asparagus, broccoli, spinach)
• Grains and enriched grains (e.g., wheat, bread, pasta)
• Dried fruits (e.g., raisins, prunes, dates, apricots)
• Soy products (e.g., extra firm tofu, tempeh, fortified soy beverages)
• Molasses
• Yeast extract spreads (e.g., Marmite, Vegemite)

References

1. https://www.unlockfood.ca/en/Articles/Iron/Managing-iron-deficiency.aspx
2. https://www.merckmanuals.com/professional/nutritional-disorders/mineral-deficiency-and-mineral-toxicity/iron-deficiency#:~:text=Besides%20anemia%2C%20iron%20deficiency,post-cricoid%20esophageal%20diaphragm.
3. https://www.merckmanuals.com/home/nutrition/minerals/iron-deficiency?query=Iron%20deficiency
4. Understanding Nutrition, by Eleanor N. Whitney et al., Nelson Education, 2013, pp. 443–451.
5. https://www.canada.ca/en/health-canada/services/nutrients/iron.html
6. https://www.mcgill.ca/oss/article/can-coffee-inhibit-absorption-iron

Article written by:

Marie-Noël Marsan, written in 2022.