Looking for the barley and pea pot from this week's newsletter? It is right here. Everything below is about the timing that makes a meal like that actually deliver its iron.
We have covered which foods carry iron and how vitamin C helps you absorb it. This one is about when you eat things, which turns out to matter nearly as much as what.
Two kinds of iron
Iron in food comes in two forms, and they behave quite differently.
Haem iron, from meat, poultry and fish, is absorbed efficiently and is relatively unaffected by whatever else is on the plate.
Non-haem iron, from plants, legumes, grains, eggs and supplements, is absorbed far less readily and is highly sensitive to what accompanies it. Which means everything below matters most if your iron comes mainly from plants.
Tea and coffee
The largest single lever, and the one most people are surprised by.
Polyphenols in tea and coffee bind non-haem iron in the gut and can reduce absorption substantially. Black tea is the strongest inhibitor. Coffee is significant, and herbal teas vary depending on what is in them.
The timing is what matters. A cup with a meal, or immediately after, is the worst case. Leave roughly an hour either side of an iron rich meal and most of the effect disappears.
This is not a reason to give up either. It is a reason to move the cup.
Calcium
Calcium competes with iron for absorption, so a large glass of milk alongside an iron rich meal works against you, as does a calcium supplement taken at the same time.
The practical answer is separation rather than reduction. Both nutrients matter, and women need plenty of each. Take them at different points in the day.
What helps
Vitamin C is the strongest enhancer, and it can substantially increase absorption of non-haem iron when eaten in the same meal. A squeeze of lemon over lentils. Tomato in a bean dish. Capsicum in a stir fry. A piece of fruit afterwards.
A small amount of meat, poultry or fish in a meal also improves absorption of the non-haem iron alongside it, which is a reason mixed meals tend to work well.
Soaking and sprouting legumes and grains reduces their phytate content, which is one of the main things binding iron in plant foods. Tinned legumes have already been through a process that helps, which is one more reason they are a sensible thing to keep in the cupboard.
What this looks like in a meal
If you would like all of that in one pot rather than in principle, our barley and pea pot is built around it. Barley, peas and greens for the iron, a good deal of lemon at the end so you absorb it, and your choice of protein through the middle.
It is also the sort of thing that reheats into lunch, which is the real test of a weeknight recipe.
A day arranged sensibly
This is not a rule, just an illustration of what the timing looks like in practice.
Coffee in the morning, on its own or with something that is not carrying your iron for the day.
Lunch with lentils or chickpeas and something acidic, so a lemon dressing or tomato through it.
Tea in the afternoon, well away from meals.
Dinner with the iron rich part of the day, vegetables, and no large glass of milk alongside it.
Nothing there requires eating anything different. It is the same food, arranged so it works with you rather than against you.
The takeaway: Plant iron is far more affected by timing than iron from meat. Tea and coffee are the biggest inhibitors, so leave an hour either side of a meal. Separate calcium and iron rather than reducing either. Vitamin C in the same meal is the strongest thing you can do to help, and it costs nothing.
The science behind this post:
- Hurrell R, Egli I (2010). Iron bioavailability and dietary reference values. American Journal of Clinical Nutrition, 91(5), 1461S-1467S. Polyphenols, phytates and calcium inhibit non-haem iron absorption; ascorbic acid and meat tissue enhance it.
- Petry N, Egli I, Zeder C, Walczyk T, Hurrell R (2010). Polyphenols and phytic acid contribute to the low iron bioavailability from common beans in young women. Journal of Nutrition, 140(11), 1977-1982.
- National Health and Medical Research Council. Nutrient Reference Values for Australia and New Zealand: Iron. Haem and non-haem iron absorption and dietary modifiers. nrv.gov.au