Plant-Based Iron Sources, Absorption, Deficiency | Plant Nutrition Wellness

Getting enough plant-based iron on a vegan or vegetarian diet can take some planning and practice, but it is possible. This article breaks down why iron requirements are higher for people following a plant-based diet, strategies to increase iron intake and absorption, and how to spot red flags for iron deficiency. 

What is iron and why do we need it?

Iron is an essential mineral with several important functions in the body (1). Some of these include:

• Forming part of haemoglobin which helps carry oxygen from the lungs to the rest of the body.
• Forming part of myoglobin, which is a protein that helps transport oxygen to muscles during exercise and daily movement.
• DNA synthesis and energy production in cells.
• Immune support

There are two different types of iron in the diet. These are haem and non-haem iron. Haem iron is only found in animal products such as meat and fish, whereas non-haem iron is found in both animal products and plant foods (2).

The main difference between the two types of iron is how well we absorb them. Unfortunately for plant-based eaters, haem iron is much better absorbed by the body than non-haem iron. Approximately 15-35% of haem iron is absorbed during digestion compared to only 2-20% of non-haem iron.

The absorption of non-haem iron is also affected by other components in foods consumed at the same time (3). This is one of the reasons that animal products such as red meat are promoted as better sources of iron than plant foods.

However, a well-planned vegan or vegetarian diet absolutely can provide adequate iron. In fact, in Australia, even for non-vegetarians, most dietary iron comes from plant foods rather than meat (2).

Iron requirements on a plant-based diet

When consuming a vegetarian or vegan diet, some nutrients must be consumed in larger quantities than what is specified for the general healthy population, iron being one of them. This is because, as mentioned previously, plant-based sources of iron are much less readily absorbed by the body.

It is recommended that all individuals consuming a predominantly plant-based diet consume 180% of the recommended daily intake specified for the general population to make sure that requirements are met (2).

Iron requirements differ greatly between genders and across different stages of life. Below is a summary of the daily requirements for vegetarians or vegans based on the values provided in the Nutrient Reference Values for Australians and New Zealanders (4).

Best plant-based iron sources

To ensure requirements are met, it is recommended to include a variety of plant-based sources of iron in the diet and ensure that each meal contains iron-rich foods.

There are a wide variety of plant-based iron sources you can choose from. These include legumes, whole grains, nuts and seeds, leafy green vegetables and dried fruit. Fortified products such as some cereals and meat alternatives also act as great sources of iron for vegans and vegetarians (2).

The following table lists the amounts of iron found in different plant foods and fortified products (5):

Legumes

Wholegrains

Nuts & Seeds

Vegetables

Other

Fortified Products

Iron-rich day on a plate

Breakfast: ~7mg
2 Weet-Bix + ½ cup soy milk + ½ cup strawberries + 30g hemp seeds

Lunch: ~10mg
Tofu nourish bowl: 150g tofu + 1 cup spinach + 1 cup roast veg (beetroot, pumpkin, sweet potato, carrot broccoli) + ½ cup quinoa + tahini dressing (1 tbsp tahini, lemon juice, maple syrup)

Dinner: ~6mg
Bean barley and vegetable stew (1 cup kale, ½ cup red kidney beans, ½ cup barley + 1 cup mixed veg) + 1 baked potato  

Snacks: ~10mg
Veggie sticks with 3 tbsp hummus
Four dried apricots + 30g dark chocolate
30g almonds
20g Milo + 1 cup soy milk

TOTAL:  ~33mg

Optimising iron absorption

Many dietary factors that can either increase (enhancers) or decrease (inhibitors) our body’s ability to absorb iron from plant-based foods.

Inhibitors

The main inhibitor is phytates or phytic acid, which is often referred to as an ‘anti-nutrient’ because it binds to minerals such as iron preventing their absorption.

Unfortunately, phytates are abundant in many iron-rich plant foods such as legumes, whole grains and nuts. The phytate content in whole grains can be reduced during processing, however, nutrients such as iron and zinc are often reduced as well. Additional ways to decrease phytates include leavening bread and soaking and sprouting legumes, grains and seeds (2, 6).

Other inhibitors include polyphenols which are found in tea, coffee, cocoa and red wine and some other minerals such as calcium and zinc which compete for absorption (2).

Enhancers

Many dietary factors can enhance iron absorption, the most helpful being vitamin C. Adding vitamin C-rich foods such as citrus fruits, kiwi fruit, strawberry, broccoli, red capsicum and white potato to your meals can increase iron absorption by up to 3 to 6-fold (2).

Some other dietary factors that can enhance iron absorption include other organic acid additives such as citric, malic and lactic acids as well as vitamin A and beta-carotene. These are high in dark leafy greens, and many orange fruits and vegetables such as carrots, sweet potatoes and apricots. (2)

Some simple tips to improve iron absorption include:

• Drink tea and coffee 30 mins before or after meals
• Soak and rinse legumes before cooking
• Add vitamin C-rich foods to your meals
• If supplementing with zinc or calcium, consume these away from iron-rich meals or snacks

Iron deficiency on a plant-based diet

Iron deficiency is the most common nutritional deficiency in the world affecting over 30% of the population across both developing and developed countries (7).

There are multiple reasons why you may develop an iron deficiency. These include (8):

• Increased blood loss:
  • Bleeding in your digestive tract: ulcer, colon cancer, regular use of medicines such as aspirin or nonsteroidal anti-inflammatory drugs (NSAIDS) such as ibuprofen and naproxen
  • Frequent blood donation
  • Frequent blood tests – especially in infants and small children
  • Heavy menstrual periods
  • Injury or surgery
  • Urinary tract bleeding
• Inadequate intake or increased requirements
• Problems absorbing iron:
  • Intestinal and digestive conditions: coeliac disease, inflammatory bowel diseases (ulcerative colitis and Crohn’s disease), Helicobacter pylori infection
  • History of gastrointestinal surgery such as weight-loss surgeries (especially gastric bypass or gastrectomy)

As such, high-risk groups for developing an iron deficiency include (2,3,8):

• Those on a restricted diet such as a vegan or vegetarian diet or restricted calorie diet (weight loss)
• Women of reproductive age – increased losses through menstruation
• Pregnant and breastfeeding women – increased needs for foetal growth
• Endurance athletes – increased losses
• Medical conditions leading to intestine inflammation or chronic blood: ulcers, Crohn’s Disease, Ulcerative Colitis, undiagnosed Coeliac disease

Iron deficiency can be categorised into three levels based on the severity of the deficiency (2).

1. Depleted iron stores – no limitations to iron supply around the body
2. Early functional iron deficiency – suboptimal iron supply to tissues but no substantial impairment to red blood cell formation
3. Iron deficiency anaemia – decreased red blood cell count, substantial functional impairment

Signs you may have an iron deficiency

Symptoms often start mild and worsen as the deficiency becomes more severe. Feeling more tired than usual is often the first tell-tale sign you may have an iron deficiency.

Common symptoms include (2, 8):

• Weakness and fatigue
• Dizziness
• Decreased immunity
• Shortness of breath
• Impaired cognition
• Increased sensitivity to cold
• Heart palpitations
• Decreased athletic performance
• Hair loss or brittle nails
• Irritation or bleeding at corners of the mouth or around the lips

If iron-deficiency anaemia goes untreated, more severe and potentially life-threatening complications can arise. These include:  

• Depression
• Heart problems
• Increased risk of infections
• Pregnant women: premature delivery, low birth weight
• Infants: higher infant mortality, delayed psychomotor development impaired cognition

If you think you may have an iron deficiency it is important to discuss any concerns with your GP.

Are you more at risk of iron deficiency being vegan or vegetarian?

It is commonly thought that individuals following a vegan or vegetarian diet are more at risk of developing an iron deficiency due to the lower bioavailability of iron in plant-based sources.

Whilst it is important to pay more attention to your iron intake if you are following a primarily plant-based diet, eating a well-planned vegan or vegetarian diet provides no increased risk for developing an iron deficiency compared to non-vegetarians (2,3). Feel free to contact our vegan nutritionists and online dietitians in Australia for more information and personalised recommendations.

Should you take an iron supplement? 

It is absolutely possible to meet your iron requirements solely from food sources when following a plant-based or vegan diet, and supplements should never be used to replace a healthy diet. However, a supplement may be necessary in some instances to resolve or avoid deficiency (3).

Due to the body’s ability to tightly regulate iron absorption from food sources, there is no evidence of adverse effects from consuming high amounts of iron from plant-based food sources. However, over-supplementation is a different story. This is because excess iron in supplements can accumulate in the body, which can be very harmful. Possible side effects include constipation, diarrhoea, vomiting, nausea, liver dysfunction, and increased inflammation in the body (3). 

There are, however, a few common side effects associated with iron supplementation that you may experience such as nausea, abdominal pain, gas, diarrhoea, constipation and black or tarry stools (3).

To avoid unnecessarily supplementing, we recommend to ‘test not guess’ and get a blood test done first through your GP before starting on any supplements. Your GP or dietitian will then be able to best guide you on whether or not supplementation would benefit you.

Thriving on plant-based iron

Following a well-planned and balanced plant-based diet can ensure that you meet your dietary iron requirements. However, in some circumstances, supplementation may be necessary to avoid or correct iron deficiency, working with your doctor and dietitian for a tailored approach. 

If you are struggling to get enough iron on a plant-based diet, or trying to correct iron deficiency but feel unsure about where to start, you can book an appointment with one of our online dietitians at The PNW Clinic today. 

Article written by: PNW Clinic Dietitian Georgia D’Andrea.