The complexities of iron: absorption, pathology and supplements

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As THE most common nutrient deficiency in the world: iron is a topic of common conversation in my world. So let’s unpack exactly what iron is and it’s relevance in our desire to perform and function optimally.

At the most basic level: iron is a heavy metal with chemical symbol Fe and atomic number 26. Naturally present in many foods, iron is an essential mineral that forms a constituent of many vital proteins and enzymes within the body. These proteins and enzymes require iron in order to efficiently transport oxygen, produce energy, support antioxidant activity, and repair DNA in our body. So yep, it’s pretty important!

There are two types of iron we absorb from food: haem iron, which is found in animal products, and non-haem iron found in plant based food. Non-haem iron is not as easily absorbed as haem iron in the body: a phenomenon referred to as being less bioavailable. Regardless of which type you consume, but especially important when you only consume non-haem sources: we need to ensure we harness the power of supportive nutrients to improve absorption of iron. As well as being mindful of minerals or chemical compounds that inhibit absorption. More on this shortly.

For Aussies, the recommended daily intakes (RDI) of iron from food are: women aged 19-50 to consume 18mg/day and for those >50 years = 8mg/day. The RDI for men is 8mg/day. For many women, this presents a challenge. But even amongst people who do theoretically consume enough iron, many are still reporting pathology results that would indicate deficiencies. Now, it’s important when assessing iron status in the body that we check all parameters. Iron, serum ferritin (the stored version of iron), transferrin (iron-binding proteins) and transferrin saturation (what percentage of your iron-binding proteins are saturated with iron) should all be tested as an absolute bare minimum. In reality, this only tells us part of the story though.

So how or why would someone present with iron deficiency (or suboptimal iron levels) when their diet seems to include enough? There’s a multitude of reasons, and why it’s important to check in with your nutritionist about your unique circumstances. But below I’ve listed a few elements worth considering (note: this list is not exhaustive).

  • Vitamin C helps to improve the bioavailability of non-haem sources of iron. This is particularly important for vegetarians and vegans. Furthermore, vitamin C is heat sensitive, meaning if you are relying on your vitamin C coming from cooked veggies: there won’t be much left for use in the body. Instead: opt for raw versions of vitamin C rich foods for optimal absorption: oranges, kiwi fruit, lemons, capsicum, tomatoes etc. A side salad would easily create this desired outcome.
  • Iron competes for absorption via the same receptor site in the gut as zinc and copper. So if you’re taking supplemental forms of these, it’s important that you discuss this with your nutritionist.
  • Calcium can bind to non-haem iron in the gut, essentially rendering it unavailable for absorption. Again, this is especially relevant if you supplement with calcium. Or if you are consuming only vegetarian or vegan sources of iron. The good news is, that vitamin C can help mitigate this problem.
  • Tannins in black & green teas and coffee can inhibit iron absorption too. So these are best consumed away from meals rather than with them. Similarly, many herbal teas can interact as well: so if you’re chronically deficient, be mindful of this effect.
  • If you have any sort of chronic digestive upset: IBS, IBD, celiac disease, or untreated worm or parasite infections: there’s a good chance your body isn’t absorbing any nutrients as efficiently as it could. I’d highly recommend seeking support from your nutritionist if this is the case, or if you suspect it might be.


So should we all just supplement with iron? This is a hard NO from me. It’s important to remember that iron is a heavy metal, and in high amounts is actually toxic to the body. No one understands this more than those who suffer from haemochromatosis: the most common inherited genetic condition in Australia, believed to affect 1 in every 200 of us. For these people, iron is absorbed extremely well, and if stores get too high, the body starts to deposit iron in other places like organs. So never ever supplement without first assessing your pathology levels. The other issue I see regularly is if someone already has an impaired digestive system, many iron supplements that are readily available (I’m looking at you Ferrograd), can cause even worse digestive symptoms. Which doesn’t help long-term absorption of food based iron. But, there are some great iron supplements on the market: usually all that require a prescription from your nutritionist, so it’s worth discussing with your practitioner which one may be most appropriate. Remember though: supplements are always just dealing with symptom management and boosting your blood levels. They do not deal with the underlying reason you have iron deficiency in the first place.

As far as food is concerned, here is a list of some of the foods highest in iron:

  • 1/2 cup spinach, cooked = 3.2mg

  • 1/2 cup swiss chard, cooked = 2mg

  • 100g chicken liver = 11mg

  • 100g beef = 3.5mg

  • 100g kangaroo = 3.2mg

  • 100g salmon = 1.3mg

  • 100g chicken = 0.4mg

  • 2 large eggs = 1.9mg

  • 1 cup soy milk = 1.2mg

  • 1/2 cup lentils, cooked = 3.3mg

  • 1/2 cup cannellini beans = 3.3mg

  • 2 Tbsp. cashews = 2.1mg

  • 2 Tbsp. pumpkin seeds = 2.5mg

  • 1 Tbsp. tahini = 0.8mg

  • 2 Tbsp. walnuts = 0.8mg

  • 1/2 cup cooked brown rice = 0.4mg

  • 1/2 cup cooked quinoa = 1.0mg

  • 1/2 cup rolled oats (dry) = 1.4mg


As with any mineral deficiency: there is often a number of contributing factors. But if you find yourself chronically iron deficient, I highly recommend getting some extra assistance (I’d love to help!), in order to get to the root cause and create lasting changes.

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