After 'where do you get your protein?', the second most common question I'm asked as a woman on an entirely plant-based (vegan) diet is probably 'where do you get your iron?'.
Let me just clarify one important point: it is a myth that vegans get less iron than meat-eaters and are at greater risk of iron deficiency anaemia. From a study on the EPIC-OXFORD cohort of over 65,000 people, the vegans in the study actually had the highest daily iron intakes (15.3mg) compared to the omnivores (13.4mg) . This observation was confirmed in an Australia study on male omnivores, vegetarians and vegans. Despite having a higher iron intake, a position paper from the Academy of Nutrition and Dietetics in the US reported that vegetarians tend to have lower iron stores as assessed by serum ferritin levels (though still within the normal range), but are not at a greater risk of iron deficiency anaemia (characterised by low haemoglobin and ferritin levels).
Why do we need iron?
Iron has many functions in the body, the most well-known being at the centre of haemoglobin, the protein which transports oxygen in the blood. A similar protein (myoglobin) is also found transporting oxygen in the muscle tissue. Iron is also required for numerous (93) enzymes, and cytochromes involved in cellular energy production (e.g. cytochrome C) and detoxification (cytochrome P450 family). Iron is also required for the production of the thyroid hormones, and has a role in the metabolism of neurotransmitters such as serotonin.
Causes of low iron levels:
- Inadequate dietary intake
- Decreased intestinal absorption due to a chronic condition, e.g. Crohn's Disease, Coeliac Disease
- Blood loss, e.g. surgery or child birth
- Heavy menstruation (periods)
- Pregnancy, when iron requirements dramatically increase
- Strenuous exercise: long-distance runners are at particular risk due to the destruction of red blood cells (haemolysis) that occurs with repetitive heel strikes against hard pavement
- Frequent blood donations
Iron deficiency vs. Iron deficiency Anaemia
It's important to note that there is a difference between being iron deficient (low stores of iron in the body which if severe enough will affect red blood cell production), and having Iron Deficiency Anaemia (characterised by low haemoglobin levels and very low/absent iron stores).
Symptoms of Iron Deficiency Anaemia include:
- shortness of breath
- thin, flat, or spoon-shaped nails (koilonychia)
- hypersensitivity to cold temperatures
- frequent headaches
- loss of appetite
- pica (craving to eat dirt or other non-nutritive substances)
- restless legs
- glossitis - inflammation of the tongue
- hair loss
- pale skin and conjunctiva (inside of the eyelids)
- heart palpitations
- reduced work productivity
- impaired memory
- impaired concentration
- apathy and depression
- low exercise tolerance (feeling exhausted after not much physical activity)
- reduced resistance to infections (e.g. more frequent colds during winter)
Haem vs. non-haem Iron
There are two types of dietary iron: haem iron and non-haem iron. Haem iron - as it is derived from blood and muscle - is only found in animal-based foods (meat, eggs, fish) whereas non-haem iron is found in both animal and plant-based foods. Because we're all herbivores here, this discussion will focus on dietary non-haem iron.
Recommended Dietary Intake (RDI) for adult men= 8mg
RDI for adult women (aged 19-51 years) = 18mg
It is recommended that vegans and vegetarians consume 80% more iron than omnivores, which brings the RDI for adult women up to a whopping 32mg per day (virtually unachievable without supplementation). However, this recommendation was based on only one study from 1991 which looked at iron absorption in two groups: one containing maximal enhancers of iron absorption, and the other containing maximal inhibitors of iron absorption (which they used as the basis for the vegetarian diet). As this study doesn't accurately reflect a balanced, nutrient-rich plant-based diet, I'd take this recommendation with a grain of salt, and instead of focusing on hitting an arbitrary number of milligrams of iron each day, follow my Practical Recommendations below.
Non-haem Iron absorption is regulated by:
-How much iron you have stored in your body, i.e. if you have lower stores, absorption from the gut is up-regulated, so you will absorb more iron from your food to try and boost your stores
-Dietary enhancers of iron absorption, and
-Dietary inhibitors of iron absorption
Enhancers of iron absorption:
- Vitamin C (ascorbic acid) - found in foods such as capsicum, tomatoes, broccoli, cauliflower, oranges, kiwi fruit, Brussels sprouts. Just 50mg of vitamin C (the amount in 1/2 a large orange) will enhance absorption by 3-6 times
- Beta-carotene (pro-Vitamin A) from orange and yellow vegetables such as pumpkin, sweet potato and carrots has been found to increase the absorption of iron from grains
- Other organic acids (e.g. citric acid) in fruits and vegetables
- Fermented vegetables (e.g. sauerkraut, kimchi)
- Lysine, an amino acid found in legumes and quinoa
- Garlic and onion - both were found to enhance the iron absorbed from whole grains and legumes (read more here)
Inhibitors of iron absorption:
- Phenolic compounds in coffee, black tea, green tea, certain herbal teas (such as chamomile and peppermint), red wine and cacao
- Calcium (in amounts greater than around 50mg), found in large quantities in fortified plant-based milks
Phytic acid (found in legumes and whole grains) is also also considered an inhibitor of iron absorption, but the effect is overcome by the addition of some vitamin C to a meal. Phytic acid is also reduced by yeast or sourdough fermentation of breads, soaking and cooking, and soaking and sprouting of grains and legumes. Phytic acid is certainly not an anti-nutrient - it has antioxidant activity and is associated with a reduced risk of numerous chronic diseases.
The top plant-based sources of iron:
- Legumes & Lentils (approx. 2-3mg per 3/4 cup cooked)
- Tofu (2.9mg per 100g)
- Tempeh (2.2mg per 100g)
- Green vegetables, particularly broccoli (1mg per 1/2 cup cooked), spinach (3.9mg per 100g cooked), bok choy (2mg per 100g stir-fried without oil), silverbeet (2.8mg per 100g boiled)
- Sweet potato (1.25mg per 250g raw), potato (1.65mg per 300g raw)
- Nuts, particularly cashews (1.3mg per 25g) and almonds (1mg per 25g)
- Seeds, particularly pepitas/pumpkin seeds (2.5mg per 25g) and sunflower seeds (1.2mg per 25g)
- Tahini (1mg per 20g)
- Whole grains, particularly amaranth (5.2mg iron per 1 cup cooked), quinoa (2.8mg per 1 cup cooked), rolled oats (1.9g per 50g), brown rice (1mg per 1 cup cooked) and wholewheat pasta (3mg per 75g dry weight)
- Molasses (1mg per 20g)
- Fresh fruit, particularly oranges (0.75mg per 200g orange), apricots (0.6mg per 200g), and figs (0.6mg per 200g)
- Dried fruit, such as dried apricots (1.5mg per 50g), dates (1.3mg per 50g) and figs (0.7mg per 50g). In saying this, dried fruit is no higher in iron than the equivalent amount (by kilojoules) of fresh fruit. Dried fruit is only higher in iron (gram for gram) than fresh fruit because it's had most of its water removed, which concentrates the iron
- Iron-fortified breakfast cereals, e.g. Weet-Bix (3mg per 30g serve)
- Dark chocolate (1.3mg per 30g serve)
- Wheat germ (1mg per 10g)
- Include a serve of a protein-rich plant foods (legumes, tofu or tempeh) with 2 meals each day
- Include vitamin C-rich fruits or vegetables (or 1/2 glass orange juice with pulp) with your iron-rich meals
- Include vegetables rich in beta-carotene with your iron-rich meals (e.g. carrot, pumpkin, sweet potato, kale, spinach)
- Choose iron-rich green leafy vegetables with meals, such as silverbeet, spinach and bok choy
- Choose whole grains and whole grain products over refined grains and their products, as iron is concentrated in the outer layers of grains (germ and bran) which is removed to produce white grains
- Avoid drinking tea, coffee, cacao or wine at meal times (1-2 hours after is okay)
- Avoid drinking plant milk fortified with calcium with iron-rich meals
- Avoid taking calcium supplements with or shortly after iron-rich meals
- Include a small handful (20-30g) of nuts and/or seeds each day
- Have your iron levels tested annually
Don't self-diagnose iron deficiency!
If you're feeling tired, please see your GP and request a blood test before buying a bottle of iron supplements. Fatigue could be related to any number of things, e.g. lack of sleep, mental health conditions or other nutrient deficiencies such as vitamin B12 or zinc.
High-dose iron supplements (e.g. Ferrograd-C) have numerous side effects (e.g. constipation, stomach upset, nausea) and excess iron within the cell reacts with reactive oxygen species, forming a highly reactive free radical (the hydroxyl radical), which has the potential to cause oxidative stress and cellular damage.
Another reason not to take iron supplements is that haemochromatosis is also a relatively common genetically-inherited condition which causes iron overload in the body, which will be made much worse by taking iron supplements, as our bodies have no mechanism to excrete excess iron.
If you are diagnosed with Iron Deficiency Anaemia:
It is likely you will be put onto a high-dose iron supplement (e.g. Ferro-grad C) or asked to have a series of iron injections to bring your haemoglobin back up until the normal range. Please make sure your GP investigates the underlying cause of your anaemia (rather than just assuming it's due to your vegan diet), as anaemia relatively uncommon and can be a symptom of a serious medical condition such as Coeliac Disease and Inflammatory Bowel Diseases such as Crohn's Disease.
Any questions? Feel free to comment below and I'll do my best to answer them.