Written by Leticia Benevides
Vegetarian, vegan and plant-based diets have been growing in popularity over the years due to health and environmental issues. However, there are some concerns regarding the adequacy of certain nutrients such as iron, while following a vegetarian diet (1).
What is iron & why is it so important?
Iron is an essential nutrient involved in multiple metabolic processes such as oxygen transport and energy production. It is required for the production of haemoglobin (a protein that gives the pigment of red blood cells responsible for oxygen transport) and myoglobin (a protein found in your muscles) (2). Iron is also involved in enzyme and DNA synthesis, cell metabolism and important for immune function. Therefore, it plays a significant role in the circulatory system, and other chemical reactions essential for life (3).
Maintaining adequate iron intake on a vegetarian diet is very important as studies have suggested that vegetarians may be more prone to iron deficiency due to concerns about its lower bioavailability (the amount absorbed by the body) from plant sources compared to non-plant sources and due to dietary inhibitors that decrease its absorption (4).
Haem & Non-haem iron
Dietary iron is absorbed in the small intestine and it can be found in two different forms:
Haem iron: present in haemoglobin and found in animal foods such as meat, seafood and poultry.
Non-haem iron: found in plant foods such as vegetables, legumes, grains, nuts, seeds, dairy products and iron-fortified foods. (5).
These two forms of iron are absorbed differently in our bodies. Haem iron has greater bioavailability and it has an easier absorption of approximately 20%-30% (6). On the other hand, the non-haem iron absorption rate is 5%-10%, which is influenced by all the different food components that can either enhance or inhibit its absorption during a meal (2).
Interestingly, according to studies in the UK, 45% of where we get our iron from in our diet comes from plant sources (non-haem iron) and less than 20% comes from meat and meat products. Iron-fortified cereals and bread make an essential contribution to iron intake in both vegetarian and non-vegetarian diets (4).
How much iron do we need?
The UK's Recommended Dietary Allowance (RDA) for iron is:
8.7mg a day for men over 18
14.8mg a day for women aged 19-50
8.7mg a day for women over 50
The UK Foods Standards Agency has reported that vegetarians do not need a higher iron requirement as requirements can be met through the consumption of a variety of plant foods containing iron and a well balanced diet (4).
What are the side effects of not having enough iron?
According to the National Diet and Nutrition Survey (NDNS), 54% of girls aged between 11-18 years old were not consuming enough iron in their diet, with amounts below the lower reference nutrient intake (LRNI), and that around 25% of women aged between 19-64 also eat below the LRNI.
The World Health Organization (WHO) have reported that 27% of the global population experiences iron deficiency which makes it the most common nutritional deficiency worldwide, particularly among young women, children and adolescents (4).
Low levels of iron can lead to iron deficiency anaemia (IDA) which is the lack of red blood cells to carry adequate oxygen throughout the body, negatively affecting cognitive development and immune function (3). The most common symptoms of IDA include:
Tiredness/weakness
Headaches
Pale skin
Shortness of breath
Sensitivity to cold
Heart palpitations
However, it is important to highlight that IDA is not always caused by inadequate iron intake. Some other causes and medical conditions include heavy menstrual periods, stomach ulcers, inflammatory bowel disease (IBD) and taking NSAIDs medications (6). If you have some of the IDA symptoms it might be worth checking your iron levels with your GP and they may decide to take a blood test or recommend iron supplementation (5).
Best sources of iron in a vegetarian diet
There are many plant based sources of iron, both found naturally and in fortified foods and drinks. Legumes, pulses, nuts, seeds and dark leafy greens are among the best. Check out our list below for the top sources (listed per 100g).
How can I increase iron absorption?
Nutrients which reduce iron absorption:
Iron derived from plant sources is not as readily absorbed and absorption can be affected by the presence of other food compounds such as, calcium, polyphenols (found in cocoa, tea, red wine and coffee), phytates (found in grains, bread and pasta) are the major iron absorption inhibitors (3,7).
Nutrients which increase iron absorption:
On the other hand, vitamin C (ascorbic acid) has been shown to enhance iron absorption, in particular, the non-haem iron which is prevalent in the vegetarian diet (6,8). Vitamin C facilitates absorption by converting Fe3+ (ferric) to Fe2+ (ferrous) iron which is in its best form for absorption (2). Foods rich in vitamin C include citrus fruits, tomatoes, kiwi fruit, berries, melons, peppers and green leafy vegetables.
Simple swaps to support iron levels
For example, if you have a cup of tea with milk for breakfast, the phenols present in the tea and the calcium present in the milk can significantly reduce the concentration of non-haem iron and therefore impact on the iron absorption of your meal (8). So instead, you can choose to have a glass of orange juice or other sources of Vitamin C in your meal such as adding berries with the cereal.
Being conscious to include foods rich in Vitamin C while consuming iron-rich foods can have a significant effect on your iron absorption levels. Another tip is to opt to consume tea or coffee in between meals rather than during the meals and to reduce phytate levels present in grains and seeds you can use techniques such as soaking and sprouting to reduce this nutrient inhibitor (5).
Plant-based recipes
Looking for meal inspiration? Check out some of our favourite plant-based recipes:
At TCN our specialist eating disorder dietitians can offer online consultations to support your health journey! Book a free 15 minute discovery call here with one of our dietitians.
Leticia Benevides
Guest Contributor
Leticia is a Registered Associate Nutritionist and Plant-based Chef passionate about using a holistic approach to support others optimise their health and improve their relationship with food. Find Leticia on Instagram at @leticiabenevides
REFERENCES:
1 Iron. Vegetarian Society. The Vegetarian Society; 2019 [Online]. Available from: https://vegsoc.org/info-hub/health-and-nutrition/iron/ [Accessed on 3 October 2022].
Aspuru K, Villa C, Bermejo F, Herrero P, López SG. Optimal management of iron deficiency anemia due to poor dietary intake. Int J Gen Med [Online]. 2011;4:741–50. Available from: http://dx.doi.org/10.2147/IJGM.S17788 [Accessed on 3 October 2022].
Young I, Parker HM, Rangan A, Prvan T, Cook RL, Donges CE, et al. Association between haem and non-haem iron intake and serum ferritin in healthy young women. Nutrients [Online]. 2018 [cited 2022 Oct 14];10(1). Available from: http://dx.doi.org/10.3390/nu10010081 [Accessed on 9 October 2022].
Saunders AV, Craig WJ, Baines SK, Posen JS. Iron and vegetarian diets. Med J Aust [Online]. 2013;199(S4):S11-6. Available from: http://dx.doi.org/10.5694/mja11.11494 [Accessed on 3 October 2022].
Zijp IM, Korver O, Tijburg LB. Effect of tea and other dietary factors on iron absorption. Crit Rev Food Sci Nutr [Online]. 2000;40(5):371–98. Available from: http://dx.doi.org/10.1080/10408690091189194 [Accessed on 3 October 2022].
Ems T, St Lucia K, Huecker MR. Biochemistry, Iron Absorption. In: StatPearls [Online]. StatPearls Publishing; 2022. Available from: https://pubmed.ncbi.nlm.nih.gov/28846259/ [Accessed on 3 October 2022].
Piskin E, Cianciosi D, Gulec S, Tomas M, Capanoglu E. Iron absorption: Factors, limitations, and improvement methods. ACS Omega [Online]. 2022;7(24):20441–56. Available from: http://dx.doi.org/10.1021/acsomega.2c01833 [Accessed on 3 October 2022].
Craig WJ, Mangels AR, Fresán U, Marsh K, Miles FL, Saunders AV, et al. The safe and effective use of plant-based diets with guidelines for health professionals. Nutrients [Online]. 2021 [cited 2022 Oct 14];13(11):4144. Available from: http://dx.doi.org/10.3390/nu13114144 [Accessed on 9 October 2022].
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