As a nation we are reasonably clued up about Iron in food and its role in the body. Majority know the fact “There is enough Iron in the human body to make a whole nail”, yet, many of us are nutritionally lacking, so why is is this?
What is Dietary Iron?
Iron exists in two chemical forms, Ferrous (Fe2+) and Ferric (Fe3+). The Ferrous form is the less stable form of Iron. In the body it goes between both forms whilst absorbing, transporting and storing. Iron also exists in two dietary forms, these are Haem and Non-Haem Iron. Haem tends to derive from animal food sources and is very well absorbed. Alternatively non-haem is absorbed from plant sources of Iron and tends to be very poorly absorbed.
There are 'helps' and there are 'hindrances' to the absorption of Iron. Those that inhibit absorption are called anti-nutrients. These include:
- Polyphenols, tannins found in tea, coffee and cola.
- Phytates, found in wheat and fibre
- Calcium, found in dairy products and green leafy vegetables.
On the other hand there are nutrients that boost the absorption of Iron. These include:
- Ascorbic Acid, otherwise know as Vitamin C. It is the most dominant nutrient that helps Iron absorb by converting Iron to the correct form for absorption. Vitamin C is present in almost all fruits and vegetables, particularly kale, bell peppers, mango and strawberries.
- Meat and Amino Acids. Iron absorption is also enhanced by the presence of amino acids from meat/animal products such as beef, chicken or eggs.
Iron is consumed in food, and undergoes 4 stages of digestion and metabolism. This begins with the Luminal phase, which consists of hydrochloric gastric acid secretion which increases the solubility of Iron. When it reaches the proximal duodenum ( region of the small intestine), Iron is absorbed, however it it not abundantly absorbed in the body. Dependent on what type of dietary Iron it is, it can absorb anywhere between 5-35%. Next, is the Mucosal Uptake, this occurs when Iron binds to finger-like structures on the duodenal lining. Currently, there is no definitive answer as to how Haem Iron is absorbed, but we do know how Non-Haem Iron is absorbed. Before it can be transported it converts to the ferrous version of Iron and passes through the membrane via transporters. Next, the Intracellular Phase, also known as storage, this attaches and stores with Ferritin. Or is taken up and transported by protein Transferrin. This is the final phase and how Iron is carried to all body structures and red blood cells [1,2].
How Much Iron Do We Need? What is it for?
Iron Requirements differ from gender to gender and from year to year.
- Young males-11.3mg/day
- Adult males-8.7mg/day
- Young and adult women-14.8mg/day
- Mature women-8.7mg/day
Women require a higher level of Iron through their fertile years because they will undergo their menstrual cycle, causing monthly blood losses and pressure on their system to produce more Iron rich blood .
Iron is the main component of our red blood cells. Without it we wouldn’t be able to carry oxygen or nutrients to our muscles and organs. According to the European Food Standards Agency (EFSA) Iron is also responsible for energy production. This is why Iron is such an essential nutrient for athletes and active teenagers. As a result of this it also prevents fatigue and feelings of tiredness. Furthermore, it’s responsible for normal cell division, a healthy immune system and elevated cognitive function.
The History of Dietary Iron
There has been evidence of its use as far back as the Egyptian Period. They used Iron Oxide (rust) to cure baldness. Whereas, according to the Ancient Greeks, it was general belief that the combination of Iron and wine would increase male fertility. Chlorosis, or Green’s Disease was discovered to be cured by Iron in 1895. Its unknown why it was every called Green’s disease, because those deficient in Iron tend to look pale white and grey, not green. It was only in 1936 that physicians Patek and Heath discovered that Chlorosis was in fact Hypochromic Anemia.
Those most likely to suffer from deficiency are Young Females, Vegetarians, Vegans and the elderly. Young women are likely to be deficient because of monthly menstrual blood losses. On the other hand, Vegetarians and Vegans will predominantly eat non-haem sources that are poorly absorbed. Additionally, their diet consists of fibre rich vegetables and grains that will inhibit efficient iron absorption. The elderly may be deficient because they have poor absorption in their small intestine. Deficiency occurs in 3 phases, these are depletion of iron stores followed by a decrease in circulatory iron and finally a reduction in red blood cell production .
Symptoms of Iron deficiency include:
- Fatigue and lethargy
- A Sore tongue
- Nail brittleness
- Dizziness and momentary fainting
- Shortness of breath.
- Pallor of membranes (pale skin, lips and eye membranes)
- Cold hands and feet
- Tachycardia, rapid heat beat
- Weakness .
Iron toxicity can be just as dangerous as deficiency, it's symptomatic and causes abdominal cramping and diarrhoea. This is most likely to occur at doses over 45mg, however people who are sensitive may react poorly to as little as 20mg .
Food Sources of Iron
Non-haem sources of Iron include tofu, wholemeal fortified cereals, legumes, broccoli, kale and dried fruits. These are not densely rich in iron and are poorly absorbed.
Haem source of Iron can be found in beef, mussels, lamb and salmon. These are the most potent sources of Iron and are most bio-available to the body.
Other ways to boost your Iron
- Try an Iron Supplement. As previously suggested Iron isn’t always well absorbed in the diet, and there are only so many steaks one can eat. A one-a-day tablet can help to boost your dietary intakes. This would be hugely beneficial for Vegetarians, Vegans, and Young women.
- Always consume your Iron sources with a form of Meat or Vitamin C.
- When eating an Iron rich meal avoid adding rich Calcium or fibre foods. This way you will get the best from your meal.
- Avoid drinking copious amounts of tea or coffee, these are rich in tannins and will prevent iron from being absorbed.
- MacPhail.P. (2012). 10:Iron. In: Mann,J. Truswell,S. Essentials of Human Nutrition. 4th ed. Oxford: Oxford University Press. Page 158-170.
- Abbaspour.N. (2014). Review on iron and its importance for human health. International Journal of Research in Medical Sciences. 19 (2), Pg. 164-174.
- BNF. (2015). Nutrition Requirements. Available: https://www.nutrition.org.uk/attachments/article/234/Nutrition%20Requirements_Revised%20Nov%202015.pdf.
- Wood.R, Ronnenberg.A. (2005). 12: Iron. In: Shils.M et-al Modern Nutrition in Health and Disease. 10th ed. Philadelphia: Walters-Kluwer. Pg. 248.
- Cafasso.J, Nall.R. (2015). Iron Deficiency Anemia. Available: http://www.healthline.com/health/iron-deficiency-anemia#Symptoms4.
- MFD. (2016). Iron Facts. Available: http://www.myfooddiary.com/Resources/nutrient_facts/nutrient_iron.asp.