🩸 Vitamin B2 and iron: does it actually do anything?

I’ve been walking through this series, one piece at a time — copper, vitamin A, B12, folate, and now vitamin B2 — and what I keep being amazed at is how many separate steps your body runs just to use iron.

Getting it in is only the beginning. You'r body also has to move it, store it, get it back out of storage, and build it into red blood cells. And each of those steps needs to be working properly. Any one of them can be the reason your iron isn’t functioning.

Riboflavin, or vitamin B2, is one that I didn’t know about. But it’s critical for our bodies to reuse the iron we already have.

So this week: what riboflavin actually does for iron and whether you’re getting enough.

Riboflavin, or vitamin B2, helps you recycle and use the iron you already have. And a surprising number of women don’t have enough riboflavin to do it well.

Your body reuses iron constantly, pulling it out of storage to build new red blood cells. Riboflavin’s active forms (the flavins) are part of that machinery. They release iron from ferritin (your iron storage protein) and keep the iron-handling enzymes running.

In riboflavin-deficient animals, iron absorption and tissue iron handling both fall, and the body’s response to iron is blunted. The strongest evidence for this is in a trial of 123 UK women in their early twenties with a marginal riboflavin deficiency. Taking 3 mg of riboflavin a day over 12 weeks, their hemoglobin rose by about 7 g/L, and women who started most deficient gained the most.

As with many other co-factors, there is no evidence that extra riboflavin does anything for iron in a woman who already has enough.

About half of reproductive-age women in the UK and Ireland are deficient. The big reason is fortification. The UK and Ireland don’t add riboflavin to flour. The US does.

Enriched US flour carries riboflavin along with its iron and folic acid, which is why outright riboflavin deficiency is rare in the US.

What still puts a woman at risk anywhere is eating little of both of riboflavin’s main sources at once: dairy and enriched grains. A low-carb or grain-free pattern of eating with little dairy or veganism without fortified foods and drive a riboflavin deficiency.

Riboflavin is concentrated in dairy, eggs, meat and fish, and fortified grains, with smaller amounts in green vegetables, nuts, and legumes.

Women need about 1.1 mg a day, and intake tracks status closely.

🥛 Take a minute to add up one normal day's riboflavin. Milk/yogurt ~0.4 mg, egg ~0.2 mg, and fortified cereal often carries the full ~1.3 mg. You need 1.1 mg/day.

🏷️ Flip over your bread, pasta or flour and look for the word "enriched." Enriched grains have B2 added back. Artisan, imported, most gluten-free and many "whole grain" products don't.

🧠 Frequent migraines? Ask your doctor about increasing your riboflavin (400 mg/day) as prophylaxis.

Here’s what caught my eye this week:

📄 The condition that's 90% women and takes two years to diagnose: Palpitations, lightheadedness, fatigue, brain fog, exercise intolerance. POTS affects up to 1% of the population, roughly 90% female, peaking between 13 and 29. In a survey of 4,835 patients, about 70% reported serious functional impairment and loss of school or work, median time to diagnosis 24 months.

🧴 A perimenopause app that reads your smartwatch launched across 39 markets: anna pulls sleep, heart rate and temperature from an Apple Watch, Garmin, Fitbit, Oura or Whoop and turns the combination into a daily suggestion, with no symptom logging. £13.99/month or £99.99/year. The company says each rule draws on more than 300 published studies.

🔎 The Washington Post discovered iron deficiency this week: Yes, eat more iron. But if you're not absorbing it, that's a different problem with a different solution.

Just sharing here what's new this week. No affiliates, no sponsorships, no freebies. A mention here isn't a recommendation.