If you are vegan or following a plant-based diet you may be wondering if you’re getting enough iron. You have heard that you don’t absorb plant sources of iron as well, so is it necessary to take a supplement to ensure you’re getting enough?
This blog will dive in to everything iron: why you need it, the different types of iron, how too little or too much can affect you, the best plant-based sources, how you can increase absorption and when supplementation may be necessary.
Why Is Iron Important?
Iron is an essential mineral in your body responsible for many important jobs. Your body uses iron to make hemoglobin, a protein in red blood cells. In fact, the majority of the iron in your body (about 70%) can be found in hemoglobin.
This is important because hemoglobin is responsible for carrying oxygen from the lungs to the rest of the body. It also transports carbon dioxide back to the lungs so you can exhale it.
Additionally, iron is involved in the production of myoglobin, a protein that helps muscles store and use oxygen.
But, that’s not all. Iron supports the proper functioning of the immune system, is required for many important enzymes, helps make hormones and is important for brain development and growth in children.
The Different Types of Iron
In the human body, iron exists in two forms: heme iron and non-heme iron.
Heme iron, found only in animal flesh like meat, poultry, and fish, is generally more easily absorbed by the body.
Non-heme iron, present in plant-based sources such as legumes, nuts, seeds, tofu, dark leafy greens, dried fruits, whole and fortified grains, is not as readily absorbed compared to heme iron. Since animals consume plants, a small amount of non-heme iron is also present in animal flesh.
Transferrin is an important protein in the blood responsible for transporting iron throughout the body. Your liver makes transferrin. When your body’s stores of iron run low, your liver makes more transferrin to get more iron into your blood.
Ferritin is the storage form of iron. Your body keeps some iron on hand for the times when you don’t get enough from your diet. Iron is stored mostly in the liver, spleen and bone marrow.
How Much Iron Do You Need?
Your daily requirement for iron is actually pretty small. The body is only able to absorb 1-2 mg of iron daily5. Beyond that amount, the rest is excreted out in your stool. However, since we absorb only a small amount of the iron we eat, we have to consume a lot more than 1-2 mg.
The Recommended Daily Allowance (RDA) for iron in adults (19-50) is 8 mg for men, 18 mg daily for menstruating women. You need more if you’re pregnant (27 mg) and less if you’re lactating (9 mg).
Adolescents ages 14-18 who are actively growing need higher iron: 11 mg for boys, 15 mg for girls. For women 50+ or non-menstruating women their requirement falls to 8 mg, the same as adult men.
There is this theory that vegans and vegetarians need 1.8 times the daily recommended amount (14 mg for men, 32 mg for menstruating women) due to iron absorption per meal being lower than omnivores.
However, as with most functions of the body, iron absorption is not that black or white but presents with a lot of variables which we’ll talk about next.
So, you would think that meat eaters would be less likely to develop iron-deficiency anemia.
While it’s true that vegetarians and vegans tend to have lower iron stores, it does not appear they are at any greater risk of iron-deficiency anemia than omnivores1. In fact, plant-based diets generally contain as much if not more iron than omnivore diets2.
Most of the iron absorption studies look at absorption rates from a single meal which tend to over-estimate the effects of diet and other inhibitors on absorption3. At the end of the day, if you are eating a variety of plant foods you are most likely meeting your iron needs.
In addition, most studies only look at Ferritin levels (iron stores) to determine iron deficiency. But, when making comparisons it’s also important to consider inflammation which can significantly raise Ferritin levels.
When inflammatory markers are factored in, such as high C-Reactive Protein, obesity and insulin resistance, there does not appear to be any difference in the occurrence of iron deficiency between vegetarians and omnivores in both men and women (who don’t menstruate)4.
The biggest factor affecting absorption is how much iron stores you have. The less stored, the more iron your body will absorb. If iron storage is high your body will absorb less.
There are natural compounds found in plant foods that have the ability to “inhibit” absorption of certain nutrients including non-heme iron. Specifically Phytates (phytic acid), Polyphenols (tannins), Oxalates, and Calcium.
- Phytates are found in whole grain breads, cereals, legumes, nuts, and seeds.
- Polyphenols are found in tea, coffee, fruit, vegetables, some cereals and legumes, cocoa and red wine.
- Oxalates are highest in spinach, rhubarb, almonds, beets, beet greens, chard, soy, raspberries)
- Calcium in food: firm tofu, soybeans, dairy, dark leafy greens, nuts and seeds and also in supplements.
The effect of phytate acting as an iron inhibitor is thought to be exaggerated in single meal studies compared to looking at whole diets5. Most phytates are removed with cooking, fermenting, soaking and sprouting. Your gut bacteria may also potentially have the ability to break down these compounds. Refer to the blog: Pros and Cons of Soy to learn more.
Plant polyphenols provide antioxidant and anti-inflammatory benefits as well as protection from developing chronic diseases and cancer6.
Polyphenols are also known to inhibit iron absorption, but it’s been shown that vitamin C (ascorbic acid) counteracts this effect (at low polyphenol doses)5. More on vitamin C when we talk about “enhancers.”
Tip: Try to avoid drinking coffee or tea with meals containing iron-rich foods (~2 hours before & after).
Oxalates are natural compounds in vegetables, fruit, nuts and grains. They have been found to bind to certain minerals especially calcium and inhibit it’s absorption. The effects of oxalates on iron absorption is questionable.
Another interesting fact is that most people contain a certain strain of bacteria in their gut (Oxalobacter formigenes) that can degrade a significant amount of oxalate on a daily basis 7.
But, if you’re still worried about oxalates affecting your iron absorption try arugula, kale or bok choy instead of spinach or walnuts and pistachios instead of almonds.
Calcium in dairy products and supplements has the potential to inhibit both heme and non-heme iron absorption. Short-term studies show more of an impact than long-term studies.
If you happen to be taking both iron and calcium supplements you would want to avoid taking them together. Ideally space them apart about 3 hours and maybe take your calcium supplement at bedtime. This will help you get the most out of both supplements.
Certain proteins such as egg protein and isolated soybean protein have been shown to decrease the absorption of non-heme iron. While egg protein does not affect vegans, soy protein definitely does. But, how much should you be concerned?
Much of the iron found in soybeans and other legumes is bound to ferritin and 22–34% of this is absorbed which is comparable to the bioavailability of heme iron (15–35%)12. Intake of tofu and soybeans has also been associated with lower risk of anemia and appear to be a good source of plant-based iron13,14.
There are a few things you can do to enhance the absorption of iron on a plant-based diet:
1. Add Foods Rich in Vitamin C
The most well known way to increase non-heme iron absorption is to pair iron rich foods with a good source of vitamin C. If you’re eating fruits and vegetables this is pretty easy to do since most fruits and veggies contain vitamin C.
A few examples of foods high in vitamin C are: kiwis, bell pepper, broccoli, strawberries, pineapple, oranges, cauliflower, cantaloupe, tomatoes, lemon, lime.
Tip: try squeezing lime juice on your black bean tacos, or add pico de gallo salsa to your bowl of beans and quinoa or add lemon to your water with meals to help increase absorption.
2. Add Garlic & Onions
I don’t know about you but I put garlic and onions in everything! The cool part about this addition is not only do they help add flavor and antioxidant benefit but they also help boost non-heme iron absorption. The fun doesn’t stop there because garlic and onions also appear to increase zinc absorption8.
So, go ahead and add garlic and onions to the mix for additional mineral enhancing power.
3. Add Sweet Potatoes & Carrots?
Beta-carotene is found in bright yellow and orange fruits and vegetables and leafy greens (carrots, kale, sweet potatoes, broccoli, pumpkin, winter squash, apricots, red and yellow peppers).
4. Cook With a Cast-Iron Skillet or Lucky Iron Fish!
Using iron containing cookware such as a cast-iron skillet is an easy way to increase the iron content of your food11. This is especially true if you’re cooking something acidic or high in vitamin C like tomatoes.
If you are already low in iron another simple way to increase your iron intake is to use a Lucky Iron Fish when you are boiling water or cooking any liquid-based meal. This tool can release 6-8 mg per use! This could be a potential alternative to taking a supplement and without the side effects.
Causes & Signs of Deficiency
Some of the main causes of iron deficiency anemia is due to:
- Not Getting Enough Iron in Your Diet – this can be due to limited access to food, inadequate intake or a poorly balanced diet.
- Blood Loss – this can happen with heavy menstrual bleeding, chronic nose bleeds, injury, post surgery blood loss, any GI abnormalities that cause bleeding (peptic ulcers) or medication like aspirin which can increase your risk for GI bleeding.
- An Increased Need For Iron – your requirements for iron increase during pregnancy and during periods of rapid growth (infants, children, adolescents).
- High Impact Exercise – endurance sports such as long distance running can cause red blood cells to break down at a faster rate due to repetitive impact.
Signs of iron deficiency anemia include:
- Fatigue, weakness
- Abnormally pale skin
- Dizziness, lightheadedness
- Shortness of breath
- Sensitivity to cold
- Increased heart rate
- Weakened immune system
- Potential hair loss or brittle, spoon shaped nails
- Sometimes you can develop a condition called Pica where you get cravings to eat non-food items (dirt, clay, ice, etc.).
Who Is Most at Risk for Iron Deficiency Anemia?
When looking at the entire world’s population, iron deficiency anemia is actually one of the most common nutritional deficiencies. So, it is important to know who is more at risk.
Those at higher risk for developing iron deficiency anemia are:
- Pregnant women – the body uses iron to make more blood to supply oxygen to the baby. Iron deficiency anemia during pregnancy can cause premature birth or low birth weight. It is recommended that you start taking 27-30 mg of supplemental iron daily during pregnancy. Taking more is not better. Most prenatal vitamins contain iron.
- Menstruating women – if you have heavy menstrual flows, especially if you’re plant-based you are more at risk.
- Children – since they have higher iron needs due to rapid growth and development they are more at risk.
- Elderly – there can be multiple reasons: chronic GI diseases creating malabsorption, poor nutrition intake, medications, etc.11.
- Endurance athletes – especially female endurance athletes who are menstruating.
- People on dialysis – besides some blood loss during hemodialysis, people with kidney failure stop efficiently producing a hormone called erythropoietin (EPO). EPO signals the body to produce more red blood cells, so with less EPO production there are fewer red blood cells causing increased risk of iron deficiency anemia.
Can You Have Too Much Iron?
The short answer is yes, too much iron can be toxic to your body. Iron overload is pretty rare because the body is usually able to regulate how much iron is absorbed.
Typically those at risk for iron overload are: people who receive blood transfusions, take high dose iron supplements or injections, and those who have a genetic condition which causes the body to absorb too much iron.
The safe tolerable upper intake of iron is 45 mg daily for males and females ages 14 years and older. For younger ages, the upper limit is 40 mg daily.
The Best Vegan Sources of Iron
Thankfully, there are a lot of iron rich plant options on a vegan diet. The key is to try to include some of these foods throughout your day (not all at one large meal) to ensure you get and absorb enough.
Iron Supplements for Vegans: Are They Necessary?
Most vegans or plant-based eaters can meet their iron needs through a balanced diet without the need for supplementation. The more variety and whole plant foods you eat the better. If you are eating a more processed diet this will put you more at risk for developing iron deficiency.
If you fall into one of the groups more at risk for deficiency (see above) then you need to pay more attention to both diet and checking lab work more regularly to make sure you are in a healthy range.
Ideally, you want to meet your iron needs through diet first. However, if you are diagnosed with iron deficiency anemia your doctor will most likely prescribe an iron supplement to help bring your levels back up to normal range. Most iron supplements are made with non-heme iron and will be from a vegan source.
You do not want to take an iron supplement long-term or if you’re not deficient. Too much iron can be toxic and cause oxidative stress to the body. If your levels are low, your doctor will determine the appropriate dosage based on your individual needs and will monitor your iron levels through blood tests.
Iron is an important mineral for growth and development, our immune system, and providing oxygen to different parts of our body.
As you can see, it is also not a straightforward mineral! There are many nuances with absorption especially with non-heme iron. However, there are many plant-based sources of iron to choose from and different ways to help increase absorption.
Consuming iron-rich foods from a variety of plant-based sources is a safer way to maintain healthy iron levels without risking toxicity.