My discussion here stems from my personal frustration with my borderline anemia, and how across the medical community the common recommendation for anemia is to eat “leafy greens and red meat
”. Why red meat? My diet is primarily plant-based, and I get frustrated when I’m told that I must eat red meat to improve my anemia (seeing as I readily eat leafy greens already). On another note even if you aren’t vegetarian recent studies have demonstrated a correlation between red meat consumption and increased incidence of mortality 12-36%, diabetes, cardiovascular disease, and cancer (1
). What really is going on? Is eating red meat necessary for improving our iron levels? The short answer is no, but you have to take a deeper look into what anemia is and how other foods you are eating can impact your ability to absorb iron. Much like how various drugs have various interactions with one another, food does too. It’s important to understand how combining various ingredients may be impacting your ability to absorb iron. On another note, I am not
a registered dietician. The steps I lay out ahead are based on evidence and research, but please consult an RD/MD for your own personal needs.
Step 1: What is Anemia?
According to WebMD Anemia is defined as low red blood cells(3
). Your red blood cells consist of hemoglobin which carries and distributes oxygen throughout your body. Normal hemoglobin is between 12-15.5g/dl for women and 13.5-17g/dl for men. If your hemoglobin is lower than normal you are considered to have anemia. There are different reasons why you may have anemia: iron deficiency, vitamin B-12 deficiency, folate deficiency, bleeding, cancers, kidney disease, liver disease, hypothyroidism, thalassemia. For this article, I’m going to focus on iron deficiency which affects 4-8% of premenopausal women due to our regular menstrual cycles. Iron deficiency anemia is the most common type of nutritional deficiency globally(4). Typically symptoms include fatigue, shortness of breath, and lightheadedness. During childbearing years women on average lose about 2mg per day compared to men who lose about 1mg (5
). This means that women need to be 2x more effective at absorbing iron than men, especially since we tend to eat less as well. The recommended daily iron intake is 20mg. However, take in mind that women during their menstrual cycle may lose anywhere from 4mg-100mg.
Step 2: Why iron?
Where does iron come into play? Well, the central component of the hemoglobin molecule is either ferrous Fe2+ or ferric 3+ (5
). The heme molecule containing iron binds to oxygen to deliver the O2 throughout the body. When you are low in iron your body’s ability to bind to oxygen and deliver the oxygen is limited leading to fatigue and shortness of breath due to your muscles not getting ample supply of O2. Once the iron is absorbed into the body it is stored as ferritin in the liver, bone marrow, spleen, and muscle tissue.
Step 3: Meat vs Plants?
So what’s the deal? What is the difference in the iron we absorb from plants vs. animals? Dietary iron is split into heme (ferrous) and non-heme iron (ferric). These are absorbed non-competitively, meaning that they have different receptors in your intestinal mucosal lining (5
). Meat produces a source of heme iron, while plants produce non-heme iron. It is true that geographical areas with higher meat consumption have a lower incidence of iron deficiency anemia. Non-heme iron is affected by various substances that diminish it’s absorption, while heme iron is not as readily affected and thus easily absorbed. So what substances affect non-heme iron absorption? Phytates, oxalates, phosphates, carbonates, and tannates. Ehh what? I’ll break those down a bit later.
Step 4: How do I improve my non-heme (plant) based iron?
The key here is timing and making sure ingredients that do affect iron absorption are consumed separately or 30-60min before a meal to reduce inhibition (6
). Each of the following categories can be prepared in different ways to also reduce their impact on non-heme iron absorption.
Phytates (Phytic Acid)
Common ingredients that contain higher levels of phytic acids:
Various seeds & nuts (pumpkin seeds, linseeds, sesame seeds, chia seeds, almonds, Brazil nuts, lentils, beans, soy, wheat)
How do you reduce the effect of phytic acid? Fermentation, cooking, sprouting, and pickling are all effective methods of reducing the content of phytic acid.
So how do I do it? I love bread and have been making my own sourdough bread for a couple of years now. The longer fermentation process reduces phytic acid but also breaks down the wheat particles making it easier to digest and lowering the glycemic index of the bread. Roasting/cooking the nuts before eating them is a simple way to reduce phytic acid. I also like to eat nuts as a snack, separately from my meals- simple solution to still getting protein but not affecting my iron absorption.
Oxalate is a bit less of a concern. It’s mostly found in rhubarb, buckwheat, black pepper, parsley, poppy seed, amaranth. Oxalates are more of a concern for those with a history of kidney dysfunction as Oxalates commonly bind calcium to iron to create crystals leading to kidney stones. 80% of most kidney stones are a result of oxalates.
The problem with phosphates is primarily due to overconsumption. On average American women consume 1,189mg while the recommended dietary allowance is 550-700mg (7
). About 10-50% of our daily phosphorus consumption comes from additives in processed foods. So your best bet is to avoid processed foods including: processed meats, sodas/colas, baked goods (shelf & mixes), fast foods, and convenience foods. Many of these foods have added phosphorus to improve shelf life and stability as a preservative. And again if you want that coca-cola just try to have it 60min prior or after your meal to reduce the inhibition. Dairy also tends to have a higher level of phosphorus.
Primary dietary sources of tannins are in tea or coffee. Wines also contain tannins that the grapes either absorb from the soil or during the aging process in oak barrels. Coffee and tea have been found to reduce iron absorption by 30-90% (depending on the study) these also affect heme iron, so even eating a juicy burger with a cup of coffee will significantly impact your iron absorption.
I’ve added calcium to the mix here because there are studies that indicate that calcium reduces iron absorption. A study by Gleerup et al
found that about 30-50% more iron was absorbed when no milk or cheese was served with lunch or dinner.
However, a more recent study
demonstrated a short term effect on reducing iron absorption but longitudinally the iron absorption seemed to normalize. Calcium in conjunction with phytates in products reduced the degradation of the phytates(9
). So just having a calcium-rich additive (i.e. a dough or cake that contains dairy) will reduce the effect that baking/cooking or fermentation will have on degrading phytates. Thus reducing your ability to absorb the iron in the other ingredients.
Step 5: Take Away, and Simple Solutions
Yeowch that was a lot to take in. My biggest take away is eating certain ingredients separately from iron-rich foods. Having dairy, tea/coffee with meals can reduce your iron absorption. However, vitamin C (ascorbic acid) is a fantastic way to increase your iron absorption. Multiple studies have demonstrated the benefits of vitamin C. Easy ingredients to add to a meal include red/green peppers, orange/juice/grapefruit, kiwi, strawberries, tomatoes, potatoes, broccoli, frozen peas, and spinach.
I love this meal example provided by Harvard:
A couple of points to highlight:
- the lemon juice is a great source of vitamin C- helps boost the iron absorption from the baby spinach and lentils!
- In inorder to reduce the phytates make sure the nuts are roasted or cooked-NOT raw
- With the lentils/beans/mustard make sure that they don’t include preservatives-if you are getting them in the prepackaged or canned form
It’s important to note that nutritional recommendations are evolving and change from year to year. Stay up to date on nutritional recommendations check out some of the links I’ve provided. I also like to compare what European recommendations are compared to US recommendations, as policymakers are influenced by lobbyists in the agricultural industry. I like to observe everything with a grain of salt and take in information from various resources.
Interested in learning more about the levels of these different minerals/vitamins in your foods? Check out Food Data Central
. It’s a pretty awesome website that will list the amount of these different substances in your foods! Another fantastic resource to determine recommended daily values: European Reference Values
. It’s an interactive website that makes it really easy based on age, gender, and other categories to determine how much of a certain product you should be consuming.
1. Pan A, Sun Q, Bernstein AM, et al. Red meat consumption and mortality: results from 2 prospective cohort studies. Arch Intern Med. 2012;172(7):555-563. doi:10.1001/archinternmed.2011.2287
2. Sinha R, Cross AJ, Graubard BI, Leitzmann MF, Schatzkin A. Meat intake and mortality: a prospective study of over half a million people. Arch Intern Med. 2009;169(6):562-571. doi:10.1001/archinternmed.2009.6
6. Morck TA, Lynch SR, Cook JD. Inhibition of food iron absorption by coffee. Am J Clin Nutr. 1983;37(3):416-420. doi:10.1093/ajcn/37.3.416
9. Hallberg L, Brune M, Erlandsson M, Sandberg AS, Rossander-Hultén L. Calcium: effect of different amounts on nonheme- and heme-iron absorption in humans. Am J Clin Nutr. 1991;53(1):112-119. doi:10.1093/ajcn/53.1.112