Aside from protein, iron is probably the most common nutrient that people tend to worry about getting enough of when it comes to switching to a vegetarian or vegan diet. But, is this concern valid? If you prefer to listen to this article, click here.
To eat meat, or not to eat meat? That is the controversial question.
I hate to be the bearer of bad news, but it turns out that yes, being fully plant-based can adversely affect iron levels. Many people who are vegetarian, especially women, tend to present with less-than-optimal iron levels more often than their meat-eating counterparts.
The good news, however, is that there are ways to make sure that you get enough iron in your diet as a vegetarian – you just have to be very intentional about it. Read on to learn about the role of iron in our bodies, what happens when we fail to get enough of it, the prevalence and causes or iron deficiency, and what you can do as a vegetarian to keep your iron levels on the up and up.
Why do we need iron?
Iron is a central part of the molecule heme, the precursor to hemoglobin, which is the molecule in our red blood cells that transfers oxygen from the lungs to tissues all throughout the body. Iron is also found in myoglobin, which is similar to hemoglobin but with functions limited to muscle tissue.
Iron is essential for many bodily functions, not just oxygen transport.
Most of the iron in our body, about 70% of it, is stored in our red blood cells. The rest is stored in enzymes and other proteins. Iron has myriad roles, including the synthesis of genetic material, energy production in the mitochondria, and of course, respiration.
What happens if we do not get enough iron?
Iron losses through menstruation, sweat, blood donations, accidents, and atrophic gastritis (inflammation of the stomach lining) are just a few examples of circumstances which can lead to low levels of iron. Not consuming enough iron can also lead to low amounts of iron stored in the body. Symptoms of low iron levels include problems concentrating, fatigue, overall weakness, shortness of breath, muscle and joint pain, headaches, and a host of other symptoms.
Headaches can be just one symptom of low iron stores.
It is important to note that even with a normal blood count and levels of hemoglobin that fall within the acceptable range, a person can still be deficient in iron.
Diagnostic criteria for iron deficiency and iron deficiency anemia, a severe form of deficiency, vary between labs, so it is best to consult with your primary care provider if you are concerned about your iron status.
How common is iron deficiency?
According to the World Health Organization (WHO), iron deficiency is the most common cause of anemia across the globe. About 25% of the global population is estimated to have some form of anemia – that’s about 2 billion people.
The most commonly affected demographics are children, pre-menopausal women, and people living in underdeveloped countries. But what about people following plant-based diets?
Is vegetarianism associated with iron deficiency?
It has long been debated whether or not vegetarians, and vegans in particular, are at greater risk for iron deficiency or iron deficiency anemia compared to omnivores. This is because the type of iron consumed in fully plant-based diets, non-heme iron, is poorly absorbed in the body compared to heme iron from animal sources. It has been estimated that 2%–20% of non-heme iron gets absorbed, while for heme iron, the absorption rate (aka the bioavailability) is around 15%–35%.
This plate of food contains two types of iron, but they are each handled differently by the body.
But does this really matter? Let’s see what the data says:
In a recent review of studies assessing the iron status of vegetarian adults, it was concluded that yes, vegetarians do have a higher prevalence of iron deficiency and iron deficiency anemia when compared to omnivores.
This review covered 13 studies that were conducted in a wide variety of countries, among them Australia, Canada, China, England, Germany, Korea, New Zealand, South Africa, and the United States. The researchers measured iron status based on ferritin concentration and hemoglobin. Across studies, the prevalence of iron deficiency was almost always higher in vegetarians compared to non-vegetarians.
The researchers also found that vegetarian females had lower serum ferritin values on average than their male counterparts, and this was especially for those who did not take supplements.
For vegans, the outcomes were even more concerning. In a study of 39 lacto-ovo vegetarian (the type of vegetarian that consumes dairy and eggs), 10 vegan, and 25 omnivorous Australian men, it was found that when iron deficiency was defined as <25 ng/mL, the prevalence of iron deficiency was 30% for vegans, 20.5% for vegetarians, and 0% for nonvegetarians. When they made the criterion for deficiency even stricter by lowering the deficiency threshold to 12 ng/mL, the prevalence of deficiency was found to be 25%, 3%, and 0% for vegans, vegetarians, and nonvegetarians, respectively.
In another study, this one conducted with American female participants, the differences were less pronounced: 27% of vegetarian and 20% of nonvegetarian women were found to have insufficient iron levels. It should be noted that this study was quite small, and contained a sample of just 15 vegans and 10 omnivores.
Of note, these studies did not all use the same definition for vegetarianism. For instance, Wilson and Ball defined a vegetarian as “an individual who consumed red meat no more than once a month, consumed chicken or fish no more than once a week.” Alexander and colleagues defined a vegetarian as “someone who never consumed red meat and consumed chicken or fish no more than once a week.”” Some research groups opted for stricter definitions, like the following: “…individuals who “ate no meat, meat products, fish or poultry but consumed both dairy products and eggs or dairy products respectively.””
Photo of a frustrated nutrition researcher trying to put together conclusions from studies with different criteria for the same variable.
This disparity in the classification of vegetarians and non-vegetarians between studies suggests that it is quite possible that some people who self-identified as vegetarian in these studies were in fact consuming meat on occasion and thus potentially deriving some benefits from it with regards to their iron stores. It’s hard to say, especially when you also take into consideration how challenging it can be to get accurate data on people’s dietary habits (see this article, and this one).
Nevertheless, overall data suggests that vegetarians, especially women, are at greater risk of iron deficiency.
But, why?
One explanation for this observation relates to how different types of iron get absorbed by the body. Non-heme iron, unlike like heme iron, is affected by inhibitors such as phytates, polyphenols, and oxalates. The irony of nature is that the best sources of iron in a vegetarian diet are also the richest sources of these substances that block iron absorption. Grains are rich in phytates, green veggies can be rich in oxalates, and common drinks like coffee are actually rich in polyphenols, which are all substances that can bind to iron and keep it from being absorbed.
Coffee: both a friend, and a foe.
Because of this, the Institute of Medicine (IOM) currently recommends that vegetarians aim to get 1.8 times the iron that omnivores are recommended to get in a day.
Another explanation is menstruation; it is not too surprising that vegetarian women in particular were more likely to be iron deficient, considering that many of these studies included women who were still at an age where they would be expected to be menstruating, and blood loss = iron loss.
What should you do if you are vegetarian?
If you are a vegetarian, there are a few things that you can do to boost your iron intake without compromising your convictions.
Tip number one is to get your iron status tested. Before you make any changes to your diet, it is best to be informed about what your current baseline levels are. That way, you can decide if you need to make changes, or if you are actually doing just fine with your current routine!
Before you start making changes, it is best to check to see if you actually need to make any changes at all!
Tip number two is to practice being intentional about reading labels and incorporating more iron-rich foods and iron-fortified foods into your diet such as beans, dark chocolate, tofu, and breakfast cereals.
Tip number three is especially beneficial if you have trouble digesting beans and experience bloating/gassiness whenever you have them. Soaking, sprouting, and boiling legumes helps to get rid of some of the antinutrients, and it makes the beans easier to digest as well.
Tip number four is to consume a source of vitamin C with your iron-rich foods. Ascorbic acid, the chemical name for this sour vitamin, helps to boost the bioavailability of non-heme iron. Generally, a serving of fruit or fruit juices will get the job done.
Fun fact: red bell peppers actually have more vitamin C than oranges!
My final tip is to make it a habit to have tea and coffee separate from meals. These beverages are rich in polyphenols, a broad class of antioxidants. However, polyphenols and iron absorption do not go well together, so it is best to have tea and coffee 1 hour before or after your iron-rich meal.
If you learned anything new or think that someone you care about could benefit from this information, share this article, and subscribe to the blog for regular updates on commonly asked nutrition questions.
Enjoy today!
References:
Alexander D., Ball M., Mann, J. The nutrient intake and haematological status of vegetarians and age-sex matched omnivores. Eur J Clin Nutr. 1994;48:538-546
Beck, K. L. et al. (2014). Dietary Determinants of and Possible Solutions to Iron Deficiency for Young Women Living in Industrialized Countries: A Review. Nutrients 6, 3747-3776; doi:10.3390/nu6093747
Dev, S., & Babitt, J. L. (2017). Overview of iron metabolism in health and disease. Hemodial Int, 21 Suppl 1(Suppl 1), S6-s20. doi:10.1111/hdi.12542
Fuzi, S. F. A., et al. (2017). A 1-h time interval between a meal containing iron and consumption of tea attenuates the inhibitory effects on iron absorption: a controlled trial in a cohort of healthy UK women using a stable iron isotope. Am J Clin Nutr, 106(6), 1413–1421. https://doi.org/10.3945/ajcn.117.161364
Haddad, E. H., Berk, L. S., Kettering, J. D., Hubbard, R. W., & Peters, W. R. (1999). Dietary intake and biochemical, hematologic, and immune status of vegans compared with nonvegetarians. Am J Clin Nutr, 70(3 Suppl), 586s-593s. doi:10.1093/ajcn/70.3.586s
National Institutes of Health. (2016). Office of Dietary Supplements - Iron. https://ods.od.nih.gov/factsheets/Iron-HealthProfessional/
Miller, J. L. (2013). Iron deficiency anemia: a common and curable disease. Cold Spring Harbor perspectives in medicine, 3(7), a011866. doi:10.1101/cshperspect.a011866
Pawlak, R., Berger, J., & Hines, I. (2016). Iron Status of Vegetarian Adults: A Review of Literature. American journal of lifestyle medicine, 12(6), 486-498. doi:10.1177/1559827616682933
Ravelli, M. N., & Schoeller, D. A. (2020). Traditional Self-Reported Dietary Instruments Are Prone to Inaccuracies and New Approaches Are Needed. Front Nutr. https://doi.org/10.3389/fnut.2020.00090
Soppi, E. T. (2018). Iron deficiency without anemia - a clinical challenge. Clinical case reports, 6(6), 1082-1086. doi:10.1002/ccr3.1529
Subar, A. F., et al. (2015). Addressing Current Criticism Regarding the Value of Self-Report Dietary Data. J Nutr. 2015 Dec; 145(12): 2639–2645. doi: 10.3945/jn.115.219634
Wilson, A. K., & Ball, M. J. (1999). Nutrient intake and iron status of Australian male vegetarians. Eur J Clin Nutr, 53(3), 189-194. doi:10.1038/sj.ejcn.1600696
World Health Organisation. (2020). Anaemia. https://www.who.int/health-topics/anaemia#tab=tab_1
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