Iron
mineral
ApprovedGeneral information about nutrients. No diagnosis, no medical advice. If you take medication, are pregnant or have a medical condition, talk to your doctor before taking supplements.
Overview
Iron contributes to normal oxygen transport in the body. Iron contributes to normal formation of red blood cells and haemoglobin. Excess iron is toxic.
Interactions
Vitamin C reduces ferric iron (Fe³⁺) to ferrous iron (Fe²⁺) in the gut, which is the only form absorbable by DMT1 transporters. This can increase non-heme iron absorption by 2-6x.
Ferrous iron (Fe²⁺) and zinc (Zn²⁺) compete for DMT1 absorption in the duodenum. Taking >25mg iron with zinc reduces zinc absorption by ~50%. Supplement at different times of day.
The inhibition is bidirectional: calcium blocks iron absorption AND iron can reduce calcium absorption when both are present in the gut lumen simultaneously. Separate by at least 2 hours.
EGCG (green tea catechin) chelates non-heme iron in the gut lumen, forming insoluble complexes that cannot be absorbed. A cup of green tea with a meal reduces iron absorption by 60-70%.
Iron and manganese are both transported by DMT1, and high iron intake significantly inhibits manganese absorption. Chronic high-dose iron supplementation can lead to manganese deficiency.
Research status
Excess iron promotes oxidative stress. High ferritin is linked to increased mortality.
Top 5 food sources
Expert opinions
NIH
The NIH UL of 45 mg/day for iron is set on GI side effects and the risk of iron overload, which can drive oxidative damage and organ dysfunction. RDAs are 8 mg/day for men and postmenopausal women, 18 mg/day for premenopausal women due to menstrual loss. NIH explicitly warns against empirical supplementation without ferritin/TSAT confirmation because men and postmenopausal women rarely need more iron. High-risk groups for deficiency include menstruating women, vegetarians, blood donors, and athletes with foot-strike hemolysis.
Recommended dose: 8–18 mg
Source: NIH
Bryan Johnson Blueprint
Johnson deliberately excludes iron from the Blueprint stack because his whole-food plant-forward diet supplies adequate non-heme iron and his ferritin labs stay mid-range. Ferritin, TSAT and hsCRP are tracked quarterly, and phlebotomy is considered if ferritin trends above 150 ng/ml. Only a documented deficiency would prompt time-limited low-dose supplementation under medical supervision.
Source: Blueprint Protocol
Dr. Strunz
Strunz insists on ferritin measurement before any iron supplementation and targets 40 to 100 ng/ml. In his view women of reproductive age are systematically undersupplied, while middle-aged men often need to donate blood to avoid iron overload. His preferred form is chelated bisglycinate (25 to 50 mg elemental, taken with 500 mg vitamin C on an empty stomach) for tolerability and absorption. He avoids combining it with coffee, tea or calcium within two hours, as polyphenols and minerals interfere with absorption.
Recommended dose: Only if deficient (ferritin < 40)
Source: Dr. Strunz
Expert profiles summarise publicly available statements. The named people do not cooperate with Stackwell and have not authorised these summaries. Not medical advice.
Never supplement without testing. Iron overload linked to organ damage.