Does coffee affect iron absorption? Tea, calcium and timing

The short answer

• −39%

  Iron absorbed from a meal with a cup of coffee, compared with the meal alone

• −64%

  Iron absorbed from the same kind of meal with a cup of tea

• 50–60%

  Less iron absorbed when a meal had 165 mg of calcium from milk or cheese

• 1 hour

  Gap before and after meals for tea and coffee, advised by India’s dietary guidelines

Key findingTea, coffee and calcium all reduce the iron you absorb from a meal. Having tea or coffee at least an hour away from meals is an easy fix. It matters most if you eat mostly plant foods, are low in iron or are pregnant.

How iron absorption works

Your body takes in only part of the iron in your food. This is called iron absorption. In one study, people absorbed less than 6% of the iron in a simple test meal.

Food has two kinds of iron. Haem iron comes from meat and fish. Non-haem iron comes from plant foods, such as dal, beans and green leafy vegetables. Vegetarian meals contain only the non-haem kind. The coffee and tea studies here measured non-haem iron.

India’s dietary guidelines note that green leafy vegetables have plenty of iron, but the body absorbs it poorly. Your body also adjusts to your needs. In a study of young Indian women, some had anaemia from low iron. They absorbed about 2.5 times as much iron from a meal as women with healthy iron.

When iron runs low, you can get anaemia. Haemoglobin, the red substance in blood that carries oxygen, drops. India’s guidelines say anaemia causes paleness, tiredness and more infections. Ferritin is a blood test that shows how much iron your body has stored.

Iron deficiency and anaemia are common in India. In the national nutrition survey, about 1 in 5 teens had iron deficiency, and more than 1 in 4 had anaemia.

Does coffee affect iron absorption? The classic study

In 1983, researchers tagged the iron in meals with tracers. That let them measure how much iron people absorbed. The volunteers had healthy iron stores.

A cup of coffee with a hamburger meal cut the iron absorbed by 39%. A cup of tea cut it by 64%. With a simple test meal, coffee had an even bigger effect. Drip coffee cut the iron absorbed by about 72%. The stronger the coffee, the bigger the drop. So does coffee stop iron absorption? Not completely, but it can cut it by a lot.

So does caffeine stop iron absorption? These studies tested coffee and tea as drinks, not caffeine on its own. India’s dietary guidelines point to tannins, natural plant compounds in tea and coffee. If you want to track your caffeine for other reasons, such as sleep, try the caffeine calculator.

Tea, chai and Indian meals

A 2008 study tested tea in 20 young Indian women. Ten had anaemia from low iron, and ten had healthy iron. They ate a rice meal on its own or with black tea.

One cup of tea cut the iron absorbed by about half: by 49% in women with healthy iron and 59% in women with anaemia. Two cups cut it by about two-thirds. The effect was much the same whether the women were low in iron or not.

The same study tested vitamin C. Adding it to the meal more than doubled the iron absorbed. India’s guidelines suggest vitamin C fruits such as guava or orange to help you absorb iron from plant foods.

None of these studies tested chai made with milk and sugar. Black tea alone cut iron absorption. In a separate study, the calcium in milk cut it too.

Does timing help?

Yes, at least before a meal. In the 1983 study, coffee drunk 1 hour before a meal didn’t lower iron absorption at all. But coffee 1 hour after the meal cut it as much as coffee with the meal.

A 2017 UK study tested tea. Twelve women ate the same porridge meal three times, two weeks apart: with water, with tea, and with tea an hour later. Tea with the meal cut the iron absorbed by 37%. Waiting an hour halved that effect, to 18%.

So the two studies don’t fully agree about drinks after a meal. They tested different drinks and meals. India’s 2024 dietary guidelines advise no tea or coffee for at least an hour before and after meals. A longer gap after meals may help more, but no study here tested it.

Does calcium block iron absorption?

Yes, in a single meal. A 1991 study from Sweden tested calcium in 126 people. Adding 300 to 600 mg of calcium to a meal cut the iron absorbed by 50–60%. Even 165 mg of calcium, given as milk or cheese, had the same effect. Calcium cut haem iron from meat too.

So does milk block iron absorption? In that study, the calcium in milk did, for that meal.

The long-term picture is calmer. A 2021 review pooled trials of calcium and iron. On average, high calcium cut the share of iron absorbed from meals by about 6 percentage points. More calcium went with lower ferritin. But calcium didn’t lower haemoglobin. The authors say keeping calcium and iron tablets apart in pregnancy is unlikely to change how many women get anaemia.

The 1991 study found one more thing. Calcium added to bread dough left more phytate in the bread. Phytate is a natural compound in grains that blocks iron. So phytate is another thing that lowers iron absorption.

Iron and athletes

Low iron is common in athletes, especially women and endurance athletes. A 2019 review found iron deficiency in about 15–35% of groups of female athletes. In male athletes, it was about 5–11%.

Hard exercise raises hepcidin, the main hormone that controls iron in the body. This helps explain why iron levels can drop in athletes. Hormones, diet, training and time at high altitude play a part too.

If you train hard and feel unusually tired, ask your doctor about a ferritin test. Only take iron tablets if a blood test and your doctor say you need them. For more on periods and training, see working out on your period.

Claims and evidence

• ClaimCaffeine is what blocks iron.

  EvidenceThe studies tested coffee and tea as drinks, not caffeine alone. India’s dietary guidelines point to tannins in tea and coffee.

• ClaimCoffee right after a meal is fine.

  EvidenceCoffee 1 hour after a meal cut iron absorption as much as coffee with the meal. Coffee 1 hour before had no effect.

• ClaimCalcium and iron must never meet.

  EvidenceIn single meals, 165 mg of calcium cut the iron absorbed by 50–60%. But across trials, calcium didn’t lower haemoglobin.

• ClaimOnly the iron in your food matters, not what you drink with it.

  EvidenceOne cup of black tea with a rice meal cut the iron absorbed by about half in young Indian women.

What this means for you

What the research can’t tell you yet

• Single meals. Most studies measured iron from one meal, not iron levels over months.
• Small, older studies. The tea studies had 12 to 20 people. The coffee study didn’t report its size, and it dates from 1983.
• Real Indian meals. No study here tested chai with milk, or meals such as dal and roti.
• Exact timing. No study here tested gaps longer than an hour.

How Bodyvault uses this research

If you log an iron supplement, Bodyvault Pro suggests keeping tea, coffee and calcium about 2 hours from your iron dose. If a lab report shows low ferritin or haemoglobin, Coach suggests iron-rich foods with vitamin C, and tea and coffee an hour from meals. It also suggests talking to your doctor, and compares your 7-day iron intake with India’s targets: 29 mg for women and 19 mg for men.

General information about fitness and nutrition, not medical advice. If you have a health condition, are pregnant or take medication, talk to your doctor before changing your diet or training.