The story always goes the same way. Fatigue, a low ferritin, an iron tablet every morning with coffee, sometimes with an orange for the vitamin C. Three months later, a ferritin that moved ten points, stomach aches, and the conclusion that iron does not work.
Most of the time, it is not the iron that does not work. It is the intake. Three series of trials, run with iron labelled with stable isotopes that are later found in red blood cells, measured exactly what gets in and what stays in the gut. They contradict three habits: the daily dose, the drink that goes with it, and vitamin C.
I do not take iron, and I advise nobody to without a test. The only time iron came up in my family's blood work, it was the other way round: my father's was slightly above the norm, not below. This is a protocol article, written for people, mostly women, who have been prescribed iron and want it to count.
of iron absorbed with 14 doses taken every other day, against 131 mg in 14 consecutive days
Stoffel 2017
absorption with a cup of coffee, −64% with tea, taken with the meal
Morck 1983
the ferritin threshold below which the WHO speaks of deficiency in an inflamed adult
WHO 2020
Hepcidin, the lock the daily dose closes
The gut does not absorb iron at will. A liver hormone, hepcidin, shuts the door when iron arrives, to avoid overload. The problem is that an iron tablet is exactly the signal that makes it rise.
Moretti and colleagues measured it in 54 young women with low stores. Twenty-four hours after a dose of 60 mg or more, hepcidin is elevated and absorption of the next dose drops by 35 to 45%. And the higher the dose, the less of it is absorbed in proportion: multiplying the dose by six, from 40 to 240 mg, only multiplies absorbed iron by three, from 6.7 to 18.1 mg. Three doses in 24 hours did no better than two in the morning.
Stoffel and the same team drew the test that counts from it: fourteen 60 mg doses, taken either fourteen days in a row or every other day for twenty-eight days, in 40 women whose ferritin was 25 µg/L or less. Every other day, the absorbed fraction goes from 16.3 to 21.8%, and the total from 131 to 175 mg. Hepcidin was higher in the daily group. Second trial, 120 mg in one dose against twice 60 mg: same absorption, but more hepcidin with the split dose.
It remained to check that this holds in genuinely anaemic women, where hepcidin is supposed to be crushed by the deficiency. It does: in 19 women with iron deficiency anaemia, at 100 as at 200 mg, absorption on the third consecutive day is 40 to 50% lower than on the first, and returns to the initial level two days later. The authors conclude that every other day is preferable, and that if the same total amount is needed, it is better to double the dose every other day than to take it daily.
What you drink with it
The second lock is in the cup. Morck and colleagues, as early as 1983, measured iron absorption from a meal with and without coffee: one cup reduces it by 39%, against 64% for tea. The useful detail is the timing: a coffee drunk one hour before the meal had no effect, while a coffee drunk one hour after inhibits as much as one taken during.
Hurrell and colleagues widened the list. Every polyphenol-rich drink reduces non-haem iron absorption in proportion to its content: black tea by 79 to 94%, peppermint by 84%, cocoa by 71%, vervain by 59%, camomile by 47%. Milk in tea or coffee changes nothing. Herbal teas, often taken to "go easy", are among the most inhibiting.
I drink tea rather than coffee, and that is exactly the kind of detail I would have ignored: tea is the worse of the two. For someone taking iron, the rule is simple. The tablet first, the drink at least one hour later.
Vitamin C, the advice that did not hold up
The advice to take iron with vitamin C comes from old absorption trials, in the laboratory. The clinical test was done in 2020: 440 adults with iron deficiency anaemia, 100 mg of iron three times a day for three months, with or without 200 mg of vitamin C at each intake.
At two weeks, haemoglobin had gained 2.00 g/dL with vitamin C and 1.84 without, a gap within the equivalence margin. At eight weeks, ferritin had risen the same. Adverse effects were identical, one patient in five in each group. The authors' conclusion: vitamin C is not essential with iron. It does no harm either. It is simply not the lever.
What you measure, and what it is worth
The third failure is one of reading. Haemoglobin only drops once stores are empty: it is the last signal. Stores are ferritin, and the WHO keeps it as the marker of stores in an otherwise healthy person, noting that a 15 µg/L threshold has a positive likelihood ratio of 51 for deficiency.
The trap is in the restriction "otherwise healthy". Ferritin is also an inflammation protein: it rises when the body is inflamed, and can show a normal value in someone whose stores are empty. The WHO draws two rules from it. In an adult with an infection or inflammation, a ferritin below 70 µg/L may already indicate deficiency, and measuring CRP alongside is recommended where inflammation is common. Conversely, above 150 µg/L in a menstruating woman and 200 in a man, the agency speaks of a risk of overload.
And it takes time. In Vaucher's trial, 198 menstruating, tired, non-anaemic women with a ferritin below 50 µg/L received 80 mg of iron or a placebo for twelve weeks. The fatigue score dropped by 47.7% against 28.8% on placebo, a real effect. But ferritin had only gained 11.4 µg/L in twelve weeks. Judging a supplementation at one month on ferritin is judging before anything could have moved.
The price: the gut, and not according to dose
Ferrous sulfate hurts the stomach, and that is not an impression. The 2015 meta-analysis, 43 trials and 6,831 adults, finds 2.3 times more digestive side effects than on placebo and 3 times more than on intravenous iron. With no link to dose in the meta-regression, which means lowering the dose is not enough to protect the stomach. Taking it less often is.
Who should not take it without a test
Two populations, for two opposite reasons. The first: a man or a postmenopausal woman with iron deficiency anaemia. The British guidelines recall that about a third of them have an underlying pathology, most often in the gut, and that unexplained iron deficiency anaemia warrants fast-track investigation, because some digestive cancers present this way, without any other symptom. The tablet fixes the number and hides the cause.
The second: people who accumulate iron instead of lacking it. Screening of 99,711 adults found 0.44% of homozygotes for the C282Y haemochromatosis mutation among people of northern European ancestry, about one in 230, and most already had an elevated ferritin and transferrin saturation without knowing it. In them, an iron supplement taken "against fatigue" feeds the overload. That is why iron is taken on a test, never on a feeling.
The protocol the trials draw
| Question | What the trials say | Source |
|---|---|---|
| How much | 60 to 100 mg of elemental iron per dose; above that, the absorbed proportion drops | Moretti 2015 |
| When | Every other day, in the morning, in a single dose | Stoffel 2017 and 2020 |
| With what | Nothing: tea, coffee, herbal teas and cocoa at least one hour later | Morck 1983, Hurrell 1999 |
| Vitamin C | Optional: same result with or without in 440 patients | Li 2020 |
| Control | Ferritin, and CRP if inflammation is suspected, at six then twelve weeks | WHO 2020, Vaucher 2012 |
| Before anything | A test, and a cause to find in a man or after menopause | Snook 2021, Adams 2005 |
What this article does not say
- That you should take iron. It says how to take it once a test has justified it. Without a ferritin, there is no decision.
- That the every-other-day rhythm has proven a better clinical outcome. It has proven better absorption, measured by isotopes. The authors themselves ask for confirmation on haemoglobin over the long term.
- That these figures apply to everyone. The absorption trials cover women aged 18 to 40 with low stores or anaemia. Nothing has been measured in men, for the reason that they are rarely deficient without a cause.
- That oral is always the right route. Intravenous iron exists, with three times fewer digestive troubles, and a faster response in some situations. That is a medical decision.
- That ferritin is enough. Under inflammation, it lies upwards. CRP alongside, and sometimes soluble transferrin receptor, settle the doubt.
« Iron is not taken like a drug you swallow, but like a door you open: every other day, before the tea, and while watching the right gauge. »
What Helix does
Iron is the textbook case of a stack line whose efficacy depends less on the molecule than on three interactions: with hepcidin, hence with the calendar; with the polyphenols of tea and coffee, hence with timing; and with inflammation, hence with how the blood test is read.
The Helix base connects these three things in one place: every-other-day intake as the default setting, tea and coffee as interactions to keep at a distance, and ferritin read with CRP, not alone. When a ferritin does not move at six weeks, the engine starts by looking at tea time.
A stack that sets the timing of each intake according to what blocks it.
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