Diet for iron deficiency
Iron deficiency is the most common deficiency disease worldwide; according to the World Health Organisation (WHO), about a quarter of the world's population suffers from iron deficiency [1]. Yet many foods contain the mineral iron. Can a healthy person get enough iron from food? Can an increased requirement be covered by food and perhaps even an iron deficiency be treated?
Iron-rich foods
You lose one to two milligrams of iron every day, but to compensate for this loss you need to take in considerably more iron: 10 mg for men, 15 mg for women is the recommendation of the German Nutrition Society; pregnant and breastfeeding women have a higher requirement [2].
Many foods contain iron, from a lot (pork liver) to a lot (legumes) to too little (dairy products). But the sufficient supply of iron from food depends not only on the iron content, but also on the absorption capacity in the body. And this depends on how the iron is present in the food. In addition, absorption is promoted or inhibited by substances ingested in parallel.
More about the determination of iron levels in the blood
The following table gives an overview of the iron content in milligrams per 100 grams of edible portion of various foods.
| Lebesnmittel | Iron mg per 100 g edible portion | |
|---|---|---|
| Hülsenfrüchte | Linsen Sojabohnen Weiße Bohnen Erbsen |
6,9 6,7 6,0 5,0 |
| Cereal products, pseudo cereals | Wheat bran Amaranth Quinoa Millet Oat flakes Whole grain rice |
16 9,0 8,0 7,0 5,0 3.2 |
| Nuts and Seeds | Flaxseeds, sunflower seeds, almonds and hazelnuts | 12,5 8,0 6,0 4,0 |
| Gemüse | basil chanterelles spinach, fresh black root field lettuce beetroot |
7,0 6,5 3,3 2,0 0,8 |
| Animal foodstuffs | Pork liver Calf's liver House yolk Bovine liver Blood sausage Mussels Beef Pork chops House meat |
22,1 11.0 7,2 7,1 6,4 5,1 2,6 1,8 0,7 |
The data are approximate values, as the composition of natural foods is subject to natural fluctuations.
Besides basil, other herbs also have a high iron content, for example cress, dandelion, parsley, dill and nettle have iron contents of 3-5.5 mg/100 g. In dried herbs the iron content is even higher: dried marjoram, thyme and basil have values of 80-120 mg/100 g.
Some breakfast cereals contain added iron, 8 mg per 100 g are allowed. The sense or nonsense of this measure is debated [12].
Resorption capacity of iron
Plant foods contain non-haem iron, which is mainly present as trivalent iron Fe3+. However, the intestinal cells can only absorb bivalent iron, so trivalent iron must be reduced to bivalent. This is done either by an enzyme produced naturally in the body or by reducing accompanying substances such as vitamin C or lactic acid. Vitamin C can increase iron availability up to fourfold. Haeme iron, which is easily absorbed, is found exclusively in animal products. The absorption rate of haeme iron is 15-35 percent, of non-haeme iron 2-20 percent [5]. According to the Association for Independent Health Advice (UGB), about 80 % of the iron in an average mixed diet falls on non-haeme iron.
The term haeme iron is composed of the syllable haem and iron. Haem are chemical complexes that have an iron ion as their central atom. Haeme iron comes from haemoglobin, the protein found in red blood cells. It is found exclusively in animal products whose blood also contains haemoglobin.
Adjustment of the resorption rate to the supply status
Our body has the wonderful ability to regulate the resorption rate depending on the iron requirement and the filling of the iron store. With sufficient iron supply, the resorption rate is on average about 10%, with empty iron stores it can rise to 30%, and in pregnant women resorption rates of over 60% have even been measured [11]. According to the latest findings, this mechanism is probably mainly controlled by the peptide hepcidin, which is why it is also called the hormone of iron metabolism [8].
Promote iron absorption
The absorption rate of non-heme iron, i.e. iron from plant sources, is only 2-20 per cent, but it can be significantly influenced by various nutritional factors. For example, the absorption rate can be increased 3 to 4-fold with the intake of vitamin C. Vitamin C, but also other acidic foods or sulphur-containing amino acids (e.g. in sunflower seeds, wholemeal flour, soybeans or peas) create an acidic environment in the stomach that promotes the reduction from trivalent to bivalent iron. Fruits and vegetables particularly rich in vitamin C are:
- Blackcurrant
- Papaya
- Strawberries
- Oranges, lemons
- Red peppers
- Brussels sprouts
- Kale
- Broccoli
- Fennel
By cleverly combining iron-rich foods with vitamin C-rich foods, the availability of iron from the diet can be significantly improved.
The absorption of non-heme iron is also improved by eating meat at the same time. The mechanism of this effect, known as the meat factor, has not yet been precisely clarified [5].
Inhibition of iron absorption
However, there are also substances that inhibit iron absorption in the intestine, so that the amount of usable iron is reduced. These include:
- Polyphenols in coffee, black tea, green tea, red wine, grape juice, millet, spinach.
- Oxalic acid in spinach, rhubarb, sweet potato, cocoa, almonds
- Vegetable proteins in whole grain products and all plants, especially legumes
- Phosphates, contained in soft drinks and processed dairy products (processed cheese, ice cream)
- Phytic acid in cereal products, maize, rice, wholemeal products, soya
Milk and dairy products are also often classified as inhibitory foods, but recent studies show that they have no effect on iron absorption [5].
Phytic acid is largely degraded by suitable preparation methods such as soaking and sprouting, thus making the iron available.
Oxalic acid is largely destroyed by cooking. Uncooked foods should not be consumed at the same time (plus or minus one hour) as foods containing iron.
For a long time, spinach was considered the vegetable richest in iron: 35 mg of iron per 100 g was attributed to it! In 1890, physiologist Gustav von Bunge found 35 mg of iron in 100 g of spinach - but it was dried! 100 g of fresh spinach have only a tenth of that, namely 3.5 mg. Nevertheless, spinach is a good source of iron: with 3.5 mg of iron, spinach is in the upper range of vegetables, and it is also rich in vitamin C, which increases the absorption rate. It should be cooked before consumption to render the oxalic acid harmless.
What can be achieved with an iron-rich diet?
We should take in ten to fifteen milligrams of iron daily, and as pregnant or breastfeeding women even 20 to 30 mg. Is this possible with a normal mixed diet, but also with a vegetarian or even vegan diet? Can you correct an already existing iron deficiency or even iron deficiency anaemia with an iron-rich diet?
Sufficiently supply the body
A normal Central European diet contains about 6 mg of iron per 1000 kcal [9]. With a daily energy intake of 2000 kcal, the recommended amount of 10 - 15 mg iron per day is just reached. One to two small fish or meat meals per week are sufficient to prevent iron deficiency in an otherwise balanced diet [4]. Vegetarians and vegans can also cover their iron requirements through food. It is important to pay attention to the combination of foods and to avoid eating absorption-inhibiting foods with iron-containing meals. Since the absorption rate of plant-based non-haem iron is lower than that of animal-based haem iron, it may be advisable to consume more than the recommended 10 -15 mg daily. Over-supply of the body by plant foods is very unlikely.
Compensate for increased demand
During pregnancy and breastfeeding, the need for iron increases and the haemoglobin level of the blood decreases. As soon as the attending physician diagnoses an iron deficiency, he will recommend taking iron supplements in order not to endanger the well-being of mother and child. Taking iron supplements as a precaution without a diagnosed iron deficiency is not recommended, as an oversupply can be harmful for mother and child. As long as there is no iron deficiency, a balanced diet can also prevent iron deficiency during pregnancy.
During breastfeeding, iron deficiency is a common phenomenon, especially in women who did not receive iron supplementation during pregnancy. In addition to the already increased need during pregnancy, there is often a high blood loss during delivery. To rule out an iron deficiency, a regular check of the functional iron and the storage iron is advisable, and the attending physician will prescribe any necessary iron supplementation.
Remedy iron deficiency
The therapy of a diagnosed iron deficiency by a mere change of diet is difficult and takes a very long time [10]. The iron stores, in which more than 1000 mg of iron are stored in the optimal case, are almost empty and must be replenished. With a balanced diet, the iron store is filled with about 5 mg of iron per day, so it would take almost 7 months to fill the store. Basically, a diagnosed iron deficiency should be treated by your doctor. Self-medication is not advisable, as both an iron deficiency and an iron oversupply can be dangerous for the body.
Remedy iron deficiency anaemia
Iron deficiency anaemia should always be treated by a specialist. The therapy includes clarification and treatment of the cause in combination with iron supplementation. The diet can also be changed to an iron-rich diet.
Conclusion
Many foods contain iron, but the body can only utilise a small part of the absorbed iron. The absorption rate of animal heme iron is significantly higher than that of non-heme iron, which can, however, be significantly increased by taking vitamin C. The daily requirement of iron can be well covered by a normal mixed diet; vegetarians and vegans can also cover their daily requirement with a targeted diet and thus prevent an iron deficiency. The increased need of pregnant and breastfeeding women should be treated in consultation with a specialist. The same applies to the treatment of iron deficiency or iron deficiency anaemia: in addition to clarification and treatment of the cause, iron supplementation is usually necessary.
