Iron supplements might impact gut bacteria

August 24, 2022

This review of research on iron supplementation and gut health suggests caution is warranted: taking a supplement prescribed to correct a diagnosed deficiency is often medically necessary, but without diagnosed deficiency, iron supplements might instead harm our vital beneficial gut bacteria.

Iron deficiency anaemia is very common worldwide - occurring across industrialised and non-industrialised populations alike. Given that iron is a key nutrient for blood formation, oxygen delivery throughout the body and is vital for good brain health, treating deficiencies to avoid any negative impacts is important.

However, many people take iron supplements when they do not necessarily have a known deficiency - maybe thinking it will give them more energy, maybe as part of a multivitamin/mineral tablet they have chosen to take, maybe thinking it could improve brain function- there could be all sorts of reasons. But this study suggests such a choice could in fact be problematic.

When you eat foods containing iron(or take supplements), you want that iron to be absorbed out of the gut and into the bloodstream, from where it can be directed to the benefit of body systems. If it instead remains in the gut it can’t provide those benefits. And more concerningly, as this study suggests, while there it could negatively impact your gut microbiome.

This research did not specifically look at the impacts of iron contained naturally in food – which is mainly haem(heme) iron (commonly eaten in meat, especially red meat and offal such as liver). Mostly the work considered people taking iron in tablet or liquid form or within fortified foods like baby cereal or formula. Haem (heme) iron from food is generally better absorbed into the bloodstream than that in supplements, so its impacts may well be different

This is quite a lengthy and somewhat complex article and I like to offer a 'takeaway' from such research: I suggest avoiding taking an iron supplement unless you have a diagnosed deficiency, and once that deficiency is corrected, stop taking the supplement.

For people without a diagnosed deficiency, I suggest getting your iron from foods such as red meat as well as other meats and always combine that with a wide array of vegetables, fruits, nuts, seeds and grains for balance. For those who prefer not to eat meat, vigilance is essential because iron from plant food sources is far less easily absorbed. Good sources are dark green leafy vegetables, beans, lentils, meat substitute products, dried fruit, cocoa powder and fortified breakfast cereals – combine all these with a good vitamin C food to boost absorption (such as citrus fruits or juice, capsicum, berries, papaya and pineapple; the dark green vegetables have the added bonus of being good sources of both).


As is usually the case – real food is best and only take a supplement if you have a diagnosed deficiency.  

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