#466: Iron Absorption from Foods & Supplements – Prof. Paul Sharp

In Podcasts by Danny Lennon2 Comments

Table of Contents

  1. Introduction
  2. Guest Information
  3. Overview
  4. Related Resources
  5. Detailed Study Notes (Premium Subscribers Only)
  6. Transcript (Premium Subscribers Only)


Iron deficiency is a prevalent issue. Worldwide, it is the leading nutritional deficiency. And although there is lower prevalence in high-income countries, a significant number of people are still affected.

Iron deficiency may be a result of too little iron coming in (i.e., via diet choices or low absorption), or from excess losses (e.g., commonly from blood losses). Understanding how these can impact iron status is crucial for both accurate diagnosis and treatment.

In relation to dietary iron, the source of iron is a common talking point, as there are two forms of iron that we can consume. Heme iron is found in meat, fish, and poultry, while non-heme iron is found in plant foods. It is known that heme iron is more readily absorbed than non-heme iron. However, there is much more to this story that makes things complicated.

To discuss some of the nuances of iron bioavailability, absorption, and metabolism, leading expert in the area Professor Paul Sharp of King’s College London is on the podcast. Prof. Sharp discusses crucial aspects of dietary iron sources, bioavailability, supplementation, and impacts in the body.

Guest Information

Prof. Paul Sharp, PhD

Paul Sharp is Professor of Nutritional Sciences and Head of Department of Nutrition & Dietetics at King’s College London. He has worked on the mechanisms regulating nutrient absorption and metabolism for over 25 years.

He has expertise in the fundamental mechanisms controlling iron metabolism at the cellular level and how these processes are regulated at nutrigenomic and epigenetic levels.

His current work addresses the impact of biofortification, agronomic practices, and food processing methods on the content and localisation of micronutrients in cereals and vegetables, and the bioaccessibility and bioavailability of vitamins and minerals from plant-based foods.

His work has been funded by awards from UKRI, UK charities and industry and his team are currently partners on several international GCRF collaborations on mineral bioavailability.


  • Dietary soures of iron and factors affecting absorption
  • Heme vs. non-heme iron: Misunderstood concepts
  • Inhibitors and enhancers
  • Discrepancy between whole diet interventions and the results of single meal studies.
  • Impact of clinical disorders and genetics on absorption
  • Iron supplements: Forms, dosing, and non-response
  • Roles of iron and aspects of metabolism

Detailed Study Notes

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  1. First timer here! Thanks for the work, Danny. Got here from your participation on Simon Hill’s podcast. I think this is going to be a great podcast to listen to detailed nutrition info, as I’m a engineer that quit his career to go back to college to study nutrition!

    I’ll check the other iron episodes, but I did miss a bit about the risks of high iron levels (and what high is). Im interested in this especially because here in Brazil I have the understanding that concerns with anemia or low iron levels are so high that people might exaggerate the other way. I’ve been through lots of renowned doctors here and the last one prescribed me a 100mg iron supplement, paired with 2g of ascorbic acid to aid absorption. That’s 1.5x what Dr. Paul called a high dose. And I was just in a low end of iron, ferritin, hemoglobin, but not close to anemic nor any symptoms. It just seems a more common practice here to “err on the higher end”, so it made me thinking about overshooting iron supplements.

    1. Author

      Hi Cadu!

      First, we do discuss some of the issues with too much iron in the previous episode with Dr. Austin Baraki. So it’s definitely a potential issue. And generally, for someone with normal levels and asymptomatic, then supplementing iron wouldn’t be recommended (unless in specific circumstances, e.g. an athlete about to start altitude training).

      In terms of the impact of supplementing at different doses, it will depend on the impact on the markers of iron status mentioned. So if someones iron status markers are all within range and they are asymptomatic, then fine. But if it starts getting high or they develop symptoms, then the doctor will likely look at their supplementation as an issue.

      Hopefully this helps! And episode 465 will certainly answer this more thoroughly.

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