Iron and your period: what to eat while you bleed

How much iron you actually lose (and why it matters so much)

When bleeding is measured rather than asked about, the figure is surprisingly small: a median of 0.87 mg of iron per cycle in healthy women and 5.2 mg in women with heavy bleeding (Napolitano et al., 2013). Under a milligram sounds like nothing. What changes the picture is repetition: a woman can expect on the order of 400 menstrual cycles across her reproductive life (Critchley and Maybin, 2011). That is the entire reason iron recommendations are higher for women of reproductive age than for men — it is not one month of difference, it is the sum of hundreds.

If you train, this hits closer to home

The number that sums up the problem: among 47 female athletes, NONE were anaemic and yet 47% had low ferritin (Nabeyama et al., 2023). In that same study, lower energy intake was associated with being low on iron — eating little and training a lot travel together. In distance runners followed for a full season, iron deficiency ranged between 26% and 57% depending on the point in the year (Pengelly et al., 2025).

• Being low on iron without anaemia is the norm, not the exception, in women who train
• Fatigue, poor recovery and sessions that feel flat show up long before anything alarming appears in a blood test
• Self-supplementing is not the answer: with no proven deficiency, iron improves nothing, and for some people it is dangerous

What to do on the plate while you bleed

Nothing exotic, and above all: do not eat less. These are the three moves with the best return.

1. 1

   Both kinds of iron, without obsessing

   Iron from meat and fish is absorbed better than iron from legumes, spinach or tofu. You do not have to choose: the practical version is that both show up across the week.

2. 2

   Vitamin C in the same meal

   Peppers, tomato, citrus or kiwi alongside the lentils genuinely change how much iron you absorb. It is the best effort-to-result trick on this list.

3. 3

   Coffee and tea, separately

   Their polyphenols block absorption. Nobody has to give them up: just do not drink them with the meal that carries the iron.

Period pain: what the evidence supports and what it does not

This is where honesty is needed, because the internet sells a lot of certainty on very little evidence. The Cochrane review of dietary supplements for dysmenorrhoea concludes there is NO high-quality evidence supporting any of them, and that safety evidence is missing too (Pattanittum et al., 2016). Omega-3 is the most interesting case: two meta-analyses find an effect on pain (Snipe et al., 2023; Prego-Dominguez et al., 2016), but that same Cochrane review, in the one analysable trial of fish oil alone, found a result favouring PLACEBO. When evidence contradicts itself like that, the honest move is to say so rather than pick the half that suits us.

When the period disappears: the sign nobody should celebrate

In some sporting cultures, losing your period gets counted as proof that you are training hard. It is exactly the reverse. The International Olympic Committee consensus describes relative energy deficiency in sport starting from one cause: taking in less energy than the exercise burns (Mountjoy et al., 2023). Losing the cycle is one of its most visible symptoms — and underneath sit others you cannot see, starting with bone.

• The classic formulation of treatment has not changed in twenty years: the first aim is to INCREASE energy availability, by eating more or training less (Nattiv et al., 2007)
• It works with less than people fear: in a randomised trial, around 330 kcal a day more was enough for the period to return in significantly more women (De Souza et al., 2021)
• It carries a price worth naming: those women gained 2.6 kg on average and 2.7 points of body fat (De Souza et al., 2022)
• And bleeding again is not the end of the road: the authors themselves warn that restoring menstruation does not guarantee restoring ovulation (Williams et al., 2025)

Where Renzy fits

The underlying problem behind almost all of the above is the same: not knowing how much you are actually eating. If logging is a photo instead of searching and typing every food, the habit survives the bad weeks — and that is when you find out whether you are covering what you burn or have spent months underneath it without noticing. That number is the one that matters for iron, for the cycle and for bone.