In this article I shortly explain how much iron we need, how to ensure you get enough iron (from plant-based diets) and what are the consequencies of subopitmal iron intake.
Iron is a trace element, meaning that the human body needs only small amounts of this mineral. Despite this, iron deficiency is the most common deficiency worldwide.
Iron is important for the formation of hemoglobin, a component of red blood cells that transports oxygen throughout the body. Iron is also needed to produce energy in our cells, and it contributes to the normal functioning of the immune system.
Different Forms of Iron
Iron is found in two forms in our food: heme iron and non-heme iron. Heme iron is found only in animal-derived foods, while non-heme iron is found in both animal and plant-based foods.
The Absorption of Iron
The absorption of iron from the average Western diet is estimated at about 15%. Vegetarians, on average, absorb about 10% of the iron from their food, as they primarily ingest non-heme iron, which the body absorbs less efficiently.
Iron is absorbed in the first part of the small intestine (the duodenum). The absorption of iron from food varies and depends on three major factors:
1.The iron supply in your body
The iron supply is the most important factor determining how much iron is absorbed. There is a certain degree of self-regulation: if the supply decreases, the body increases iron absorption from the small intestine. The total amount of iron in the body is 3 to 4 grams, with about 25% stored in the liver, spleen, and bone marrow. Research shows that the absorption of heme iron can increase to over 40% when iron reserves are nearly depleted.
2.The form in which iron occurs in food (heme or non-heme)
The body absorbs about 25% of heme iron from food. The amount of non-heme iron absorbed can vary between 1% and 10%.
3.The presence of other nutrients (and anti-nutrients)
Certain substances in food can increase the absorption of non-heme iron. For example, vitamin C helps the body absorb non-heme iron more efficiently. Consuming vegetables or fruits rich in vitamin C with meals can improve iron absorption.
On the other hand, phytic acid, found in whole grains, legumes, and nuts, inhibits iron absorption. To minimize this inhibitory effect, you can soak these foods in water for a few hours before cooking. Afterward, rinse them thoroughly and cook as usual.
High calcium intake can inhibit the absorption of both heme and non-heme iron.
Oxalic acid, present in raw spinach or sorrel, and tannins, found in coffee, tea, and red wine also inhibits iron absorption.
It is important to note that studies on nutrients and iron absorption often examine their effects in isolation. In reality, when considering the total diet in the long term, there are no specific nutrients that need to be avoided solely because they inhibit iron absorption.
Iron Deficiency
Iron deficiency is the most common nutritional deficiency worldwide. Women of reproductive age, vegan or otherwise, are particularly prone to iron deficiency due to blood loss during menstruation. Pregnant women are also at increased risk, as the blood volume increases during pregnancy. Vegan women are considered a high-risk group as well.
Iron deficiency is not always caused by inadequate intake. Excessive blood loss (e.g., from an accident, childbirth, surgery, or heavy menstruation) can also lead to iron deficiency. Other causes may include infections, reduced absorption in the intestines, or prolonged use of certain medications like painkillers.
Iron deficiency anemia shares many symptoms with B12 or folate deficiency anemia, making it difficult to diagnose without a blood test. Common symptoms of all types of anemia include fatigue, decreased performance, difficulty concentrating, apathy, and a weakened immune system which results in being prone to viruses. Specific symptoms of iron deficiency include brittle and spoon-shaped nails, dry skin, hair loss, and inflammation of the mouth’s mucous membranes. Restless legs syndrome is also associated with iron deficiency. Because iron is crucial in hemoglobin production (the red pigment in blood), a deficiency may also lead to pale skin.
How Much Iron Do We Need?
In the Netherlands, the recommended daily allowance of iron varies by gender and age. Children need 8 mg of iron per day, men of all ages and women over 50 need 9 mg per day, while women of reproductive age need 16 mg (to compensate for iron loss during menstruation).
Iron in Plant-Based Diets. Vegan Sources of Iron
Here are some plant-based foods that are excellent sources of iron, with the amount of iron per 100 grams of food (The data source is Food Data Central of the US Department of Agriculture):
- Dark chocolate (70-85% cacao solids): 12 mg
- Tahini: 9 mg
- Pumpkin seeds: 8.8 mg
- Hemp seeds: 8 mg
- Chia seeds: 7.7 mg
- Beans: 5 mg (adzuki beans) – 7 mg (Lima beans)
- Lentils: 5-6.5 mg
Too Much Iron?
Excess iron can damage the liver and increase the risk of liver cancer, cardiovascular diseases, and type 2 diabetes. High doses of iron (more than 45 mg per day) can cause acute gastrointestinal issues such as nausea, vomiting, and diarrhea.
Persons with the hereditary condition hemochromatosis (affecting about 0.5% of the population) should avoid excess iron. Hemochromatosis patients should not take iron supplements and should follow a diet tailored to their condition.
The European Food Safety Authority (EFSA) has not established a tolerable upper limit for iron, but it has recommended a safe intake level. For adults aged 40 and older, the maximum safe intake is 40 mg per day.