What is iron?
Iron is a trace mineral, an inorganic substance required by the body in small amounts for a variety of different functions.
It is often referred to as “the oxygen carrier” and known for its role in normal energy metabolism, but its roles go beyond that.
We need to have sufficient iron in our daily diet, with the requirements depending on sex, age and physiological state. You can have too much or too little of it, and you shouldn’t take any supplements before speaking to a health professional.
Different types of iron
Iron exists in several oxidation states, but there are only two forms present in the human body which are:
- Ferrous iron (FE2+)
- Ferric iron (FE3+)
The two dietary forms of iron are:
- Haem iron (found in flesh foods)
- Non-heam iron (found in flesh and plant foods)
Functions & benefits
Each haemoglobin molecule can bind with 4 oxygen molecules.
Iron is vital for the synthesis of haemoglobin (a protein contained in red blood cells), and therefore for the transport of oxygen and carbon dioxide to and from cells – which makes it essential for energy production.
Furthermore:
- Iron is an essential component in many enzyme reactions
- Iron is necessary for the activation and proliferation of immune cells, and therefore plays an important role in the immune system
- Iron contributes to normal cognitive function and the cognitive development in children
- Iron is required for the metabolism of drugs and foreign substances that need to be removed from the body
- Iron is a component of myoglobin, an oxygen storage protein found in muscle tissue which is used when we use our muscles
Iron absorption
Iron absorption depends on its source, as well as on individual factors like health, iron status and age. Haem iron represents approximately 10% – 15% of the dietary iron and its absorption is over 25%. Non-haem iron on the other side accounts for 90% of the dietary iron but with a much lower absorption of approximately 5-15%.
The absorption of non-haem iron can be increased if consumed with vitamin C – so think about adding vitamin C rich foods like peppers, broccoli, kale, Brussels sprouts, parsley, kiwis or citrus foods to your meals, or drizzle some lemon juice over your leafy greens!
On the other hand, foods containing phytates (grains and legumes), calcium (milk and dairy), tannins (especially in black tea), phosphate (in fizzy drinks), and foods high in oxalates are associated with a decreased absorption of iron, as are antacids.
Research indicates that a reduced absorption is unlikely to cause significant harm in people with healthy iron levels, but it could be problematic for those with iron deficiency. This doesn’t mean that you shouldn’t drink tea for example – just avoid having it with your main meals and any iron-rich foods.
For vegetarians and vegans it is generally recommended to multiply the recommended iron intake by 1.8 times to compensate for the reduced absorption of non-haem foods.
Anyone on a plant-based diet also needs to be aware of the possible negative effect of phytates on iron absorption, especially as these could form a large part of the diet. Food processing and preparation methods, which include milling, heat treatment, soaking, germination, and fermentation, can be used to remove or degrade phytate to a varying extent and improve the absorption of iron (and other minerals). Consuming vitamin C along with the meal can also counteract the effect. Please do not completely cut out foods containing phytic acid as they normally have a number of health benefits.
Iron metabolism
The metabolism of iron involves a series of processes. Iron normally enters through the intestinal mucosa and is oxidized from ferrous to ferric iron in the process, and this absorption mechanism modulates the rate at which iron enters.
When iron stores are high for example it no longer passes through but gets trapped by the mucosal cells of the intestine to be eliminated.
Iron deficiency
Iron deficiency is the most frequent nutritional deficiency in the world, affecting about 25% of the global population and particularly young women and children.
Iron deficiency can be a result of extended periods of inadequate iron intake (especially in women), in pregnancy when higher levels are needed, or with excessive blood loss.
Aneamia is well-known as a result of iron deficiency, although it’s important to highlight that other deficiencies (including of vitamin B6, B12, folic acid, zinc, manganese) can all contribute to anaemia too.
Excessive iron
On the other side, iron overload can sometimes occur in a disorder called hemochromatosis where the normal regulation of iron absorption is impaired, as well as some other rare metabolic disorders.
Iron toxicity from food sources is rare (but it can happen). Taking too much iron in the form of supplements can lead to a number of side effects and health risks, and very high doses can be fatal, especially if taken by children.
Consuming too much iron over time may cause large deposits of it to form in the liver and other tissues, leading to diabetes, heart disease and liver damage.
Always speak to a health professional before taking any supplements.
Symptoms of iron deficiency
Some of the most typical symptoms of iron deficiency include:
- Pale skin
- Sore tongue
- Fatigue or listlessness
- Dizziness
- Loss of appetite
- Nausea
Anaemia is a clinical diagnosis based on the haemoglobin levels in the blood and symptoms of anaemia can also be caused by a lack of vitamin B12 or folic acid.
Recommended daily amount
The UK RDA varies according to age, sex and body weight, with dietary iron required to cover basal iron losses, menstrual losses and growth needs.
The RDA increases from newborn throughout childhood years.
- For males aged 11 – 18 years the UK recommendation is 3 mg / day, and this goes down to 8.7 mg / day for adult males.
- For females aged 11+ it is 8 mg / day, and it remains at that level throughout adulthood. In the UK there is no increment for pregnancy or lactation (although there is in other countries).
NOTE: Never take any iron supplements before first checking your iron serum levels. There is no physiological mechanism for iron excretion, and overuse of iron supplements can lead to iron overload. There are also various forms of iron supplements available, always speak to your doctor or a health professional to find out which form is best for you best and your specific health needs.
Food sources of iron
Iron is widely distributed in foods.
The best food sources of haem iron include:
- Red meat
- organ meats
- Chicken
- Shellfish such as clams, oysters and mussels
The best food sources of non-haem iron include:
- Dark leafy green vegetables (spinach, cabbage, broccoli, kale, collard greens, rocket)
- Parsley
- Pulses
- Legumes (see note above ref phytates)
- Tofu
- Pumpkin seeds, sesame seeds
- Quinoa
- Almonds, cashew nuts, Brazil nuts, walnuts
- Dried fruits like apricots, prunes, raisins
- Fortified foods, including wheat and oats
Anyone consuming a healthy, varied diet should get enough iron from their diet.
A healthy, balanced and nutrient-dense diet is key (remember to “eat the rainbow”!), and both nutrition and lifestyle are huge contributing factors to your physical and mental wellbeing.
As always, if you have any questions or comments regarding this post then please feel free to get in touch or check out my 1:1 consultation package if you interested in a personalised programme.
Thank you for reading and keep well x
