How to optimize iron intake on a plant-based diet:
As a dietitian I often get asked how to optimize iron on a plant-based diet. It is commonly thought that vegans/vegetarians can’t meet their iron needs with plant foods alone when in fact iron deficiency is no more prevalent in this group as it is in omnivores1. This belief likely stems from the fact that iron found in plant foods is less bioavailable than iron found in animal foods. Additionally, plant foods contain other compounds that can hinder the absorption of iron. Fortunately, these factors can be easily mitigated and a carefully planned plant-based diet that includes iron-rich foods regularly can be an excellent way to ensure your meeting your needs.
In this article I will be debunking this belief and providing some tips and hacks on how to optimize iron absorption on a plant-based diet.
What is iron?
Lets start with some quick basics…
Iron is a mineral that plays a vital role in our body. It’s needed in the production of proteins that bind and transport oxygen throughout our bodies. It also plays many other key roles in our bodies which is why it is pertinent we consume a variety of iron-rich foods throughout each day.
There are two types of iron: non-heme (found in plants and animals) and heme (found in animals). Non-heme iron is absorbed less efficiently than heme iron and other aspects of the diet can impact its absorption1. Some stress choosing meat as your primary source of iron due to the higher bioavailability of heme iron, but when considering sources of iron, and really all food choices, we need to look at the larger picture. Yes – heme iron in meat is more bioavailable – but meat also comes with less beneficial components such as hormones, saturated fat and cholesterol. Instead, opting for lentils as a source of iron, which contain 6.6mg per 1 cup, allows you reap other benefits such as higher fibre, vitamin and mineral intake – without the hormones, saturated fats and cholesterol.
How much do I need?
The RDA for menstruating adults is 18mg/day and 27mg/day for pregnancy. For non-menstruating adults, the RDA for iron is 8mg/day.
The Institute of Medicine recommends that plant-based eaters (vegetarians/vegans) consume 1.8 times the normal RDA for iron due to the lower digestibility of non-heme iron in plant foods. This means women of childbearing age following a vegan or vegetarian diet need to aim for 32.4 mg of iron per day. However, this recommendation is based on limited data and does not consider enhancers or inhibitors of iron absorption so aiming for the standard RDA is sufficient unless you have iron deficiency or anemia.
How can I ensure adequate iron intake?
Iron bioavailability varies widely between foods and requirements depend on the overall make up of the diet and the presence of both inhibitors and enhancers of iron absorption.
Compounds that have been shown to inhibit iron absorption are phytates, polyphenols, tannins and calcium. These compounds inhibit absorption by binding to iron creating mineral-inhibitor complexes that the body is unable to absorb. This does not make inhibitors bad for us! Research shows phytates and polyphenols actually have anti-inflammatory effects and they are found in nutrient-rich foods loaded in fibre. We just need to be mindful of them and take the steps necessary to improve the absorption of iron.
Compounds that inhibit iron absorption:
Phytates
- Phytates are one of the main inhibitors of iron absorption. They are found in legumes, whole grains, nuts and bran.
- Preparations that reduce phytates in food and improve bioavailability of iron are sprouting, soaking, cooking and the presence of vitamin C1.
Tannins and Polyphenolic compounds
- Found in tea, coffee, cocoa and nuts.
- When aiming to optimize your absorption of iron in your diet it’s best to consume coffee and tea at least an hour before or after.
Calcium
- Found in dairy and fortified plant-based milks, calcium supplements.
- If consuming dairy/fortified plant-based products it’s best to serve between, instead of with meals to enhance iron intake
Compounds that enhance iron absorption:
Vitamin C
- The absorption of non-heme iron is significantly increased when paired with vitamin C.
- When preparing meals pair non-heme iron-rich foods with vitamin C rich foods such as bell peppers, tomatoes, citrus fruits, strawberries, etc.
- Example: if I am having lentil soup for dinner I will often add a squeeze of fresh lemon (vitamin C) to help enhance the absorption of iron in the meal.
Beta-carotene & Allium Vegetables
- Beta-carotene is found in carrots, sweet potato, apricots, etc.
- Examples of allium vegetable are garlic and onions
What are the best plant-based iron sources?
The list is extensive and there are many plant-based iron rich sources to choose from. These are just a few of my go-to’s.
Beans/soy:
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White beans, canned (1 cup = 8.3 mg)
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Lentils (1 cup = 6.9mg)
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Black beans (1 cup = 4.8 mg)
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Edamame, shelled (1 cup = 4.7mg)
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Firm tofu (1/2 cup = 3.1mg)
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Chickpeas (1 cup = 3.1 mg)
Vegetables:
Green peas, cooked (1 cup = 2.6mg)
Spinach (1 cup raw = 0.5mg, ¼ cup cooked = 0.28mg)
Kale (1 cup raw = 1mg, ¼ cup cooked = 0.5mg)
Nuts/seeds, other:
Blackstrap molasses (2 tablespoons = 7.2mg)
Tahini (1 tbsp = 0.9mg)
Hemp seeds (1 tbsp = 1.1mg)
Pumpkin seeds (1 tbsp = 1mg)
Chia seeds (1 tbsp = 0.8mg)
Dried apricots (3 apricots = 0.6mg)
Grains & Starchy vegetables:
Tri-colour quinoa (½ cup cooked or 40ml [30g] dry = 1.5mg)
Steel-cut oats (½ cup dry = 3.89mg)
**Iron estimates taken from the Canadian Nutrient File, https://food-nutrition.canada.ca/cnf-fce/index-eng.jsp.
Favourite food combinations to improve iron absorption:
- Lentil soup with a squeeze of fresh lemon
- Veggie tofu stir fry (broccoli, cabbage, garlic, onions, etc.) with a fresh squeeze of lime
- Soaked steel-cut oats with strawberries, pumpkin seeds, hemp seeds and chia seeds
There you have it folks – as you can see a well-planned plant based diet that utilizes the strategies above can ensure you are meeting you iron needs.
References:
1. American Dietetic Association and Dietitians of Canada 2003. Position of the American Dietetic Association and Dietitians of Canada: vegetarian diets. Can. J. Diet. Pract.
