When discussing a plant-based diet, iron is often brought up as a nutrient of concern. This most certainly is a valid concern because there is a relationship between some cases of iron deficiency and a plant-based lifestyle. While low iron levels are not necessarily a concern for all vegetarians, there are definitely those who do find it a challenge to obtain enough dietary iron without eating meat. This doesn’t mean it is impossible though, just that it takes a little work and understanding of which foods contain iron, along with an awareness of how to best promote its absorption.
WHO IS MOST AT RISK?
While many people can find themselves with low iron stores or with iron deficiency anemia (low hemoglobin as a result of low iron), there are several groups of people that are at higher risk. The reasons for these low iron levels can usually be boiled down to either high body requirements for iron (such as in periods of rapid growth), high blood losses (as seen in some women with heavy menstrual flows), suboptimal dietary intake and/or poor iron absorption. Considering this, those most at risk are:
- Infants and children
- Women of childbearing age (i.e. premenopausal women)
- Pregnant women
- Vegans and vegetarians
- Those suffering from medical conditions which affect gastrointestinal absorption (i.e. celiac disease or inflammatory bowel disease) or cause blood loss (i.e. peptic ulcer).*
*Iron deficiency from blood loss is a serious medical condition and needs to be treated by a doctor. For those with absorption issues, the underlying cause of the malabsorption must be addressed before any increase in dietary iron will make an impact.
So, why do we care so much about iron anyway? Well, iron is needed by the body to maintain healthy blood cells, specifically our hemoglobin cells, which transport oxygen throughout the body. Iron is also involved with a number of enzymatic reactions, synthesis of DNA, nerve transmission and protein synthesis. Symptoms of low iron are:
- Irregular heartbeat
- Shortness of breath
- Cold hands and feet
- Poor appetite, poor growth and behavioural problems (in children)
- Strange food cravings (like dirt or clay)
Since this article is focusing on a plant-based diet, let’s talk about what the studies have found in relation to the iron status of vegetarians. Like many nutrition studies, the results regarding iron deficiency rates in vegetarians have been inconsistent. Some studies show no difference in iron deficiency rates between vegetarians and non-vegetarians while others certainly show evidence for an increased risk of low iron stores and iron deficiency. One interesting review found that although Western vegetarians had lower iron stores (or less body iron), the rate of clinical iron deficiency anemia was not different between vegetarians and non-vegetarians. “Western” vegetarian diets, in this context, is emphasized as they tend to be more diverse and of higher quality than vegetarian diets in developing countries. There was, however, an association between more restrictive vegetarians diets and iron deficiency anemia. These findings could be an indication why there is so much variation in the research regarding rates of iron deficiency in vegetarians. It could very well be due to the variation in vegetarian diets themselves - there are so many ways to do a plant-based diet and some ways are more balanced and healthy than others. If you choose to restrict a number of foods beyond those which come from animals, you may certainly run the risk of excluding essential nutrients, including iron.
HEME VS. NON-HEME IRON
No article about iron and the vegetarian diet is complete without a brief comparison between the two types of dietary iron, heme and non-heme. If you’re already well versed in the differences between the two, feel free to skip ahead. If you’re still in the dark a bit about the different types of dietary iron, this section is for you.
Both plant and animal-based foods can contain iron. Heme iron is found in meat, fish and poultry, while non-heme iron is found in various plant-based foods. The main thing we need to know about these two types of iron, is that heme iron is easier for our body to absorb (15-35% absorbed) while non-heme iron is not as efficiently absorbed (only 2-20%). This is why, or at least one reason why, vegetarian diets are at a disadvantage when it comes to obtaining iron.
Despite the fact that heme iron is much more easily absorbed by our body, non-heme iron is more abundant. In general, the non-heme iron content of meals is usually much greater than that of heme iron. Even meat contains both a mix of heme and non-heme iron. So interestingly, and despite its lower bioavailability, non-heme iron supplies more towards our body’s iron pool than heme iron.
FACTORS INFLUENCING ABSORPTION
Iron is a bit of a particular nutrient in that there are a number of factors influencing its absorption. These factors include:
Your current iron status:
That’s right, you heard that correctly. The amount of iron you absorb is dependent on your current iron stores. Iron is a nutrient that is fairly tightly regulated. As such, when your iron stores are low, it becomes easier for your body to absorb it. Absorption may be increased as much 300-400% when total body iron is low. For this reason it can be sort of challenging to predict exactly how much iron a person can absorb from a certain food, as each body’s thirst for iron is different and will change as your body’s iron status changes.
Vitamin C, or ascorbic acid, is the primary iron absorption enhancer in plant-based diets. The good news about vitamin C is that it is quite abundant, particularly in a plant-based diet. Vitamin C is found in a number of fruits and vegetables which generally (or, ahem...should be) making up a big part of your diet (this is true for both vegetarian and non-vegetarian diets alike). The even better news about vitamin C, in relation to its iron enhancing powers, is that it is effective against all the iron inhibitors found in our diet. This is true of both naturally occurring and synthetic vitamin C (i.e. taken as a supplement or added to foods). One study found that the addition of as little 150 mg of vitamin C increased iron absorption in a phytate-rich test meal by 30% (see more about phytate below).
While vitamin C may be the most abundant and effective iron enhancer, there are several other food components that also help the absorption of non-heme iron, although to a lesser extent. These components include citric acid (found in citrus fruits) and fructose (the sugar in fruit). Alcohol is also said to increase iron absorption but using alcohol as a strategy to improve iron levels really isn’t a great idea (actually, it’s a terrible idea!).
The absorption of non-heme iron is also enhanced by the presence of meat, fish or poultry which is often referred to as the MPF Factor. However, since this article is geared towards obtaining enough iron on a plant-based diet, I won’t go into too much detail about this. That being said, for any semi-vegetarians (those who eat meat occasionally) or pescatarians (vegetarians who consume fish) it can be a helpful factor in enhancing iron absorption.
One last iron enhancer that deserves a mention is cast iron. While not a food itself, cooking with cast iron pans and utensils can increase the amount of iron in a meal. Transfer of iron from the pan to the food is seen most when cooking foods that are moist and slightly acidic.
There are a number of factors that work against our body’s ability to absorb non-heme iron. You’ll notice, as I go through this factors, that they are found in some pretty nutritious foods. This means that if our iron is low, it really isn’t really a wise strategy to completely omit these food from our diet.
Phytate, or phytic acid, is the most abundant iron inhibitor in plant-based diets. Found in legumes, whole grains and nuts, phytate binds to iron and prevents it from being absorbed. The good news is the phytate content of foods is reduced by soaking, fermentation and boiling (which reduces phytates by 20%). It may also be that those who consume phytate-rich foods on a regular basis develop an improved ability to absorb non-heme iron, despite the presence of phytic acid, as found in one study, however, more research in the area is needed.
Other iron inhibitors include:
- Tannins (tannic acid)
- Found in coffee, tea and chocolate.
- Found in coffee, tea, wine and various fruits and vegetables.
- Calcium and dairy products
- Egg and soy protein
- There is some indication that an egg can reduce iron absorption by 28%
REMINDER: WE EAT FOODS NOT NUTRIENTS
As you can see, there are a number of factors which influence the absorption of dietary iron. Considering that the majority of foods with iron inhibitors also provide us with other valuable and essential nutrients, it is not sensible to cut these foods from our diet. If increasing sources of plant-based iron and vitamin C in our diet is not sufficient in raising our total body iron, then it may be a good idea to take a look at these inhibitory components - this may mean cutting down on some of the worse offenders (and finding equally nutritious and iron-friendly alternatives), or rearranging when we eat these certain foods.
One important thing to remember is that we eat foods, not nutrients. Our meals will always have forces that enhance or reduce absorption of nutrients, including iron. That's just how it is and our body is made to handle this. There’s not really anyway of getting around completely avoiding the factors which compete with or inhibit nutrient absorption. While we can plan our meal to increase absorption of a needed nutrient (like iron), it’s not practical to think of our food like that all the time. It’s really not necessary to get too caught up in complicated rules about which foods can and can’t be eaten together. While little dietary tweaks can help improve nutrition, obsessively worrying about which foods can be eaten together certainly is not healthy. If you find yourself confused about how to plan a diet that maximizes your individual nutrition needs, you may benefit from the help of an experienced nutrition professional.
HOW MUCH DO YOU NEED?
Before we get into which foods contain iron, it’s good to get an idea of how much iron we actually need. Below is a chart of the Recommended Daily Allowance (RDA) for iron. As you can see, women (especially pregnant women), infants, and children have the highest iron needs.
The above iron recommendations assume you will be getting a mix of heme and non-heme iron. For those whose primary iron source is non-heme or plant-based, it has been suggested that recommended intake should be 1.8 times the RDA, to account for the poor bioavailability of non-heme iron. This would make the daily iron requirement for those following a plant-based diet:
- Babies (7-12 months): 19.8 mg/day
- Children (1-3 years): 12.6 mg/day
- Children (4-8 years): 18 mg/day
- Children (9-13 years): 14.4 mg/day
- Teen Boys (14-18 years): 19.8 mg/day
- Teen girls (14-18 years): 27 mg/day
- Men (19-50 years): 14.4 mg/day
- Women (19-50 years): 32.4 mg/day
- Pregnant women (19-50 years): 48.6 mg/day
- Lactating women (19-50 years): 16.2 mg/day
- Adults (51 years and older): 14.4 mg/day
SOURCES OF NON-HEME IRON
- Tofu (3/4 cup - 2.4-8.0 mg)
- Lentils (¾ cup - 4.1-4.9 mg)
- Beans - white, navy, kidney, pinto, black (¾ cup - 2.6-4.9 mg)
- Pumpkin seeds, roasted (¼ cup - 4.6 mg)
- Molasses, blackstrap (1 tbsp - 3.6 mg)
- Chickpeas (¾ cup - 3.5 mg)
- Spinach, cooked (½ cup - 2.0-3.4 mg)
- Tempeh (¾ cup - 3.2 mg)
- Tomato puree (½ cup - 2.4 mg)
- Soy yogurt (¾ cup - 2.1 mg)
- Edamame (½ cup - 1.9-2.4 mg)
- Potato, cooked with skin (1 medium - 1.3-1.9 mg)
- Snow peas (½ cup - 1.7 mg)
- Dried apricot (¼ cup - 1.6 mg)
- Prune juice (½ cup - 1.6 mg)
- Sesame seeds (1 tbsp - 1.4 mg)
- Hummus (¼ cup - 1.5 mg)
- Almond butter (2 tbsp - 1.1 mg)
- Oatmeal, instant (¾ cup - 4.5-6.6 mg)
- Cream of wheat (¾ cup - 5.8 mg)
- Soda crackers (6 crackers - 1.5-2.3 mg)
- Bread, whole wheat (1 slice - 1.1 mg)
- Egg noodles, enriched (½ cup - 1.2 mg)
Sample Meal Plan
To help illustrate how to plan for enough iron, the following is a sample meal plan highlighting some plant-based iron-rich foods. This meal plan is based on the needs of a woman of childbearing age, aiming for an adjusted RDA of 32 mg iron per day. This meal plan indicates iron-rich foods in bold, while amount of iron is in brackets. Vitamin C rich foods are italicized.
- 3/4 cup instant oatmeal (5.5 mg)
- 3/4 cup soy yogurt (2.1 mg)
- 2 kiwis
- 1/4 cup dried apricots (1.6 mg)
- 1/4 cup roasted pumpkin seeds (4.6 mg)
- Lentil soup with 3/4 cup lentils (4.9 mg), 1/2 cup tomato puree (2.4 mg) & 1/2 cup kale (1.3 mg)
- 6 x soda crackers (0.8 mg)
- Almond milk
- 1/4 cup hummus (1.5 mg)
- Red pepper and broccoli (0.52 mg)
- Stir fry with 3/4 cup tofu (3 mg), 1/2 cup snow peas (1.7 mg), 1/2 cup broccoli (0.52 mg), shredded carrots and red cabbage (cooked in a cast iron pan)
- 1/2 cup parboiled rice (1.5 mg)
- Steamed almond milk
TOTAL IRON: 31.98 MG (plus any additional iron transferred from cooking in a cast iron pan)
As you can see, it is possible to get enough iron - even at the higher iron recommendation for vegetarians. As we've aimed for a slightly higher amount of iron than the actual RDA, we don't necessarily need to completely restrict those foods with iron inhibitors. Remember your body has a pretty impressive ability to know when it needs more iron and can ramp up it's receptivity to iron when your stores are low. The important thing to take note of is which plant-based foods are rich in iron and vitamin C and to include these foods in your diet each day.
A FEW WORDS ABOUT IRON SUPPLEMENTS
As much as I believe in the power of food, there is definitely a time and place for iron supplements. If you have severely depressed iron levels or iron deficiency anemia, iron supplements are necessary for a quick and efficient iron repletion. It is very important note that the use of iron supplements should always be directed by your doctor, who can monitor your progress and iron levels on an ongoing basis. Iron supplements should not be taken without a doctor’s recommendation, as excess iron can lead to iron overload. Please note, the amount of iron in a multivitamin is not a problem. The supplements referred to here are 'iron only' supplements which provide a higher dosage of iron than in a general multivitamin.
If your doctor recommends iron supplements it is still important to focus on obtaining enough dietary iron. The hope is that the supplements will top up your iron and help you obtain normal hemoglobin levels, while an iron rich diet will keep iron stores at a normal level once supplements are discontinued.
While on iron supplements your doctor may recommend taking them along side vitamin C (i.e. a glass of orange juice) to boost absorption AND take them away from any dairy products, multivitamins or supplements that may inhibit absorption. This way you can maximize the efficiency of the supplements.
To answer the question of whether or not you can get enough iron on a plant-based diet - yes, you most certainly can. A diet the excludes meat and animal products can be healthy and does have a lot of proven health benefits, if done the right way.
Do you have to work a little harder to get enough iron, if you aren't eating meat? Yes, but that doesn't mean it's impossible. Armed with a little bit of knowledge regarding which plant-based foods are rich in iron, along with foods that both enhance and inhibit its absorption will go a long way.
If you find yourself a bit perplexed about how you can meet your iron needs or are excluding a large number of foods beyond which are from animals, consult an experienced Registered Dietitian to give you some guidance.