The science
How iron really works.
Low iron is rarely a mystery. Follow it from your plate to your blood, see where it gets stuck, and read the studies behind each step.
- steps from plate to blood
- 7steps from plate to blood
- kinds of iron, absorbed very differently
- 2kinds of iron, absorbed very differently
- exit door a hormone can lock
- 1exit door a hormone can lock
The journey
From your plate to your blood.
Iron does not simply arrive. It is freed, let through a door, let out by a hormone and carried again. Every step is a place where it can stall.
It plays by itself. Pick a step, use the arrows or swipe the picture.
It starts on your plate
Meat and fish bring heme iron. Beans, greens, eggs and iron tablets bring plant iron, the kind that needs help.
Two kinds of iron
Not all iron counts the same.
Meat and fish carry heme iron, which has a door of its own in your gut. Everything else, iron tablets included, is plant iron: how much gets in depends on what sits next to it.
Heme iron
Meat, fish, shellfish
- Helps
- Nothing extra needed
- Blocked by
- Calcium only
Plant iron
Beans, greens, seeds, eggs and iron tablets
- Helps
- Vitamin C and colourful vegetables
- Blocked by
- Coffee, tea, matcha, bran and calcium
Iron tablets count as plant iron: same help, same blockers.
What gets in the way
The cup next to your plate.
Coffee, tea, matcha and bran hold plant iron back. Calcium holds back both kinds. None of them is bad: they just need their own hour.
- Coffee1 h before or 2 h after
- Black and green tea1 h before or 2 h after
- Matcha3–4 h before and after
- Cocoa and chocolate1 h before or 2 h after
- Bran and fibre powdersPhytates. Soak, sprout or add vitamin C
- Spinach, chard, rhubarbOxalates. Add vitamin C
- Dairy, tahini, almonds, tofu, chiaCalcium. 3–4 h from any iron
Only calcium blocks both kinds. Iron tablets count as plant iron.
- Coffee and tea1 h before, 2 h after
- Matcha3–4 h each side
- Milk, yogurt, cheese3–4 h each side
- Coffee with meat or fishFine from ferritin 30
Normal is not optimal
In range is not the same as enough.
A lab range describes the people who were tested, and many of them are low on iron too. The program treats 50 µg/L as the minimum and 70 to 100 µg/L as its goal.
- Lab range 10–120What is common among the people tested
- Minimum 50Under this, stores are low whatever the lab says
- Optimal 70–100Where people feel and function well
The 70 to 100 band is the program's goal, not a diagnosis. Your doctor reads your result with the rest of your blood count.
The research
What the studies say.
Each step above rests on published research. Here it is in plain words, with a link to every study.
- 01
Hemeiron from meat and fish is absorbed far better than plant iron, and little else on the plate changes that.
Hurrell R, Egli I. Am J Clin Nutr. 2010Find it on PubMed - 02
24 his about how long one iron dose keeps hepcidin up, so the next day's dose gets in less.
Moretti D, et al. Blood. 2015Find it on PubMed - 03
Every other daylet more of each dose in than taking iron daily, in women with low iron stores.
Stoffel NU, et al. Lancet Haematol. 2017Find it on PubMed - 04
1 hbefore a meal, coffee did not hold its iron back. With the meal, or an hour after, it did.
Morck TA, Lynch SR, Cook JD. Am J Clin Nutr. 1983Find it on PubMed - 05
Vitamin Cin the same meal counteracted the phytates in grains and beans that hold plant iron back.
Hallberg L, Brune M, Rossander L. Am J Clin Nutr. 1989Find it on PubMed - 06
Calciumin a meal lowered the uptake of heme and plant iron alike.
Hallberg L, et al. Am J Clin Nutr. 1991Find it on PubMed - 07
Under 50µg/L of ferritin with normal hemoglobin: in women with periods, iron eased tiredness more than a placebo.
Vaucher P, et al. CMAJ. 2012Find it on PubMed - 08
Hepcidinrises with inflammation and locks the gut cell's exit door, so iron stays out of the blood.
Ganz T. Blood. 2011Find it on PubMed
Written from these studies and the program's own material. It is not medical advice, and it is waiting for review by a clinician.
Now find your weak link.
The app reads your blood test, asks what a careful doctor would ask, and points to the step where your iron gets stuck.