Humans need iron for cell growth and production of red blood cells in our blood – amongst many other important processed in the body! (1). However, the National Diet and Nutrition Survey (NDNS) discovered that 54% of girls aged 11-18 years old were consuming amounts of iron that were below the lower reference nutrient intake (LNRI). The LRNI is the amount of nutrient that is adequate for the people who have low requirements (approximately 2.5% of the population) (2). The majority of us need more than the LNRI. Thus, over half of young girls in the UK are eating far too little iron.
The dietary iron picture does not get much brighter as we get older. 27% of women aged 19-64 years eat below the LNRI. The recommended daily intake of iron changes depending on our sex and age. The recommended intake for females increases from 8.7mg/day to 14.8 mg/day when their period starts. This is a huge difference which is often not adapted for by any dietary change. Iron deficiency is a lot less common in men due to the absence of periods and pregnancy. However, their recommended intake does increase by around 3 mg/day during puberty and 12% of males aged 11-18 years consume below the LRNI (2). Therefore, poor dietary iron intake is definitely an issue in both females and males.
So, we need to help teenagers, especially young girls, understand that they need more iron and why it’s important. The NDNS clearly states that teenage girls are not eating enough iron. It is possible they are not aware of the increased needs or they do not know what to eat. Two major issues that could be aided by education in schools.
Iron in the diet
There are two forms of dietary iron; Heme iron which is found animal foods and non-heme iron which is found in plant foods such as grains, legumes, nuts and seeds. Heme iron is easily absorbed by the body, but non-heme iron must undergo a chemical change before it is absorbed. Heme iron gets absorbed more easily by our gut (approximately 25% of the iron consumed gets absorbed) (1,3). On the other hand, non-heme iron is much more affected by other dietary factors that limit its absorption (Figure 1).
For instance, if you have a cup of milky tea with your breakfast. The tannins (a type of plant chemical ) in the tea, and also the calcium in the milk, may inhibit the absorption of the non-heme iron in your breakfast (1, 4). Whereas, if you choose a glass of vitamin C-rich orange juice instead, this will increase the uptake of iron. In addition, if you wanted to absorb the high iron content of kale then you would eat it with tomatoes or red peppers, that are rich in vitamin C, perhaps in a stew-like dish.
| INHIBITORS | ENHANCERS |
| Phytic acid – cereals | Vitamin C |
| Tannins – tea, wine, berries | Citric acid |
| Calcium | Meat |
Figure 1. The dietary factors that affect iron absorption (1, 3-5)
Another problem arises when we look at the commonest sources of dietary iron the UK. The NDNS found that cereals are our main source of iron, especially pasta, bread and rice (2). Nevertheless, iron in wheat is stuck inside a single layer of cells named aleurone cells which are resistant to digestion in the body. The aleurone trap and the phytic acid hugely limits the absorption of dietary iron from cereals (5). To try and tackle this issue, iron is added in to white flour after it is milled. Fortified cereals can be helpful contributors to your dietary iron intake. (1)
The second and third most consumed sources of iron are meat and vegetables/potatoes, respectively (2). As more of us are cutting down on meat products for environmental/health/ethical reasons, it is important to know how to get more iron from your diet whether you are an omnivore, vegetarian or vegan. The Food Medic veganuary post has further information on plant-based iron sources.
Good advice may start with “Eat more vegetables” and be conscious of adding sources of vitamin C with your meal and less phytic acid (an inhibitor of absorption found in grains, nuts and legumes). Kale, cabbage, cauliflower, broccoli, tomatoes and oranges are all great plant-based sources of iron and vitamin C. Often when a person is diagnosed with iron deficiency anaemia (IDA) they are prescribed iron tablets with little discussion about their diet. Health care professionals should be aware of the complications of iron absorption and know how to advise a patient on what to eat to increase intake. It is completely possibly to consume enough iron as a vegetarian, vegan or omnivore but advice would differ in these groups.
Iron deficiency anaemia presents with tiredness, fainting, lightheadedness, pale skin, shortness of breath and can cause heart palpitations. It is important to note that there are many other causes of IDA other than failing to consume enough dietary iron (1). These include:
- Heavy menstrual period
- Pregnancy
- Stomach ulcers
- Taking NSAIDs
- Inflammatory bowel disease
- Bowel cancer
If you have some of the symptoms of anaemia it would be worth speaking to your GP who can do a simple blood test to check your iron levels.
So absorbing non-heme iron can be quite tricky but if you eat lots of green, leafy vegetables in combination with a vitamin C-rich food then you should have it cracked!
References
(1) García López, S., Rubio, A., Poza, V., Bermejo, & García López, S. (2011). Optimal management of iron deficiency anemia due to poor dietary intake. International Journal of General Medicine. https://doi.org/10.2147/IJGM.S17788
(2) Gov.uk. (2018). National Diet and Nutrition Survey – GOV.UK. [online] Available at: https://www.gov.uk/government/collections/national-diet-and-nutrition-survey
(3) Beck, K. L., Conlon, C. A., Kruger, R., & Coad, J. (2014). Dietary determinants of and possible solutions to iron deficiency for young women living in industrialized countries: A review. Nutrients. https://doi.org/10.3390/nu6093747
(4) Zijp, I. M., Korver, O., & Tijburg, L. B. M. (2000). Effect of tea and other dietary factors on iron absorption. Critical Reviews in Food Science and Nutrition. https://doi.org/10.1080/10408690091189194
(5) Borg, S., Brinch-Pedersen, H., Tauris, B., & Holm, P. B. (2009). Iron transport, deposition and bioavailability in the wheat and barley grain. Plant and Soil. https://doi.org/10.1007/s11104-009-0046-6
Feature image: Adolfo Felix via Unsplash
