The Most Essential Metal: Iron in Your Diet
According to the WHO, over 2 billion people in the world suffer from iron deficiency – it is the most widespread nutrition disorder on Earth. While in the West anaemia is less prevalent, you should still arm yourself with some scientific knowledge about iron, since the labels on foods can be very misleading!
Why we need iron
Almost everyone knows that the body uses iron to make red blood cells. Indeed, the protein hemoglobin is responsible for delivering oxygen from the lungs to all other organs, while myoglobin stores oxygen in muscles and liver. At any given time, our body contains 3-4 grams of iron.
Anaemia, or lack of iron, means that our tissues do not get enough oxygen to perform their work. The result is a feeling of exhaustion and fatigue. Other symptoms of iron deficiency include cold hands, dizziness, and pale skin.
The one organ that uses up most oxygen – around 20%! – is the brain. Therefore, iron-deficient people, whose brain does not receive enough oxygen, experience a lack of focus, inability to concentrate, and problems with memory. In children, it can result in long-term learning disabilities.
How much do I need?
An adult man needs around 8mg of iron a day, a woman around 18 mg (since a lot of it is lost during periods), a pregnant woman needs 27 mg, and a teenager 11-15mg (more data here). Note that excessive iron intake is dangerous, too – it can lead to nausea and vomiting.
Heme vs non-heme
Now that we have seen that iron is essential, let us note that it comes in two forms. Heme iron is found in the form of hemoglobin and myoglobin in animal tissue, such as meat. The foods with the highest levels of heme iron are seafood, liver, beef, and sardines. But even in meat, heme iron consitutes only about 50% of the total iron contents. The rest is non-heme iron, which is also the only type of iron found in dairy and eggs and all plant foods. The richest plant sources of non-heme iron are beans, lentils, dark leafy greens and grains, such as millet and buckwheat.
What’s the difference? The absorbtion levels. We absorb around 25-30% of heme iron in our food, but only 10% of non-heme iron (our digestive system needs to spend lots of additional energy to transform non-heme iron – more info here). You have to keep this in mind when reading labels on your food: while 100 grams of soy beans contain a whopping 16mg of iron, you will absorb less than 2mg.
In combination with some foods, even less non-heme iron is absorbed! For example, beans naturally contain phytic acid that reduces the bio-availability of non-heme iron by 50% (more details here). Another iron inhibitor is calcium, which makes milk a really weak source of iron. Interestingly, polyphenols present in black tea and coffee also reduce the absorption of iron; drink your tea between the meals!
Not all is lost
Luckily, there are ways to increase the bio-availability of iron in plant foods: the best is vitamin C! Studies show that regular intake of vitamin C during meals that contain iron can have a dramatic effect on the levels of iron in your body. To achieve that, accompany a plate of beans or tofu with some cabbage, bell peppers, cauliflower, or a tomato salad. And don’t forget that glass of fresh orange juice! For more sources of vitamin C, see our earlier article.
While not many of us are truly anaemic, you should still take measures to get enough iron in your food. A balanced diet is a result of careful consideration and much knowledge, but it’s worth it: we are what we eat.