Does Coffee Inhibit Iron Absorption? What Are the Effects of Having Too Much Iron?

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Coffee and common herbal teas impair iron absorption, which may help explain some of their benefits.

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Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

In my videos on tea, I caution not to drink with meals, because it can inhibit the absorption of iron from foods anywhere from 26 to 99 percent, perhaps depending on the brewing time, brand, or how strong it is. What about the inhibition of food iron absorption by coffee?

When I was first looking this up, I ran across this study on the effects of discontinuing coffee intake on the iron status of Guatemalan toddlers. I’m thinking they must be talking about breastfeeding mothers or something, but no, coffee is one of the first liquids given to infants in Guatemala. I did not know that!

Anyway, the inhibition of food iron absorption by coffee. A cup of coffee reduced iron absorption from a hamburger meal by 39 percent, as opposed to a 64 percent decrease with tea. So, not as bad as tea, but still significant blockage. And just like with the tea, the stronger the coffee, the more iron absorption was impeded. In terms of timing, no decrease in iron absorption occurred when coffee was consumed an hour before a meal, but waiting an hour after the meal to drink the coffee didn’t seem to help. This can be probably explained by the fact that it may take up to nearly two hours to clear a meal from the stomach; so, starting an hour in, the coffee can catch up to the food.

Now, you can reverse the effect of tea or coffee by adding orange juice to a meal, or even better an orange, or any source of vitamin C-rich food. The vitamin C boosts iron absorption, which is good for people who are borderline anemic, but for many, the blockage of iron absorption from coffee may actually be a good thing.

Iron is a double-edged sword. On the one hand, iron is an essential element vital for blood production. On the other hand, iron is a potent pro-oxidant. So, maybe the reduced risk of type 2 diabetes associated with coffee consumption is due to the inhibition of iron absorption by coffee.

See, the risk of type 2 diabetes increases with the increase in the amount of ferritin in your blood, which is a measure of your iron stores. So, higher iron stores, higher diabetes risk. It’s the same thing with the risk of gestational diabetes during pregnancy. So, you need to make sure you’re getting enough iron, but not building up too much iron in your body. How do we know it’s cause and effect?

Because if you randomize diabetics to something like old-fashioned bloodletting, but instead of leeches, they just donate blood a couple times to lower their iron stores, and those in the blood donation group had better blood sugar control, better insulin secretion, and less insulin resistance. Iron depletion improves artery dysfunction in type 2 diabetics as well.

It’s the same thing with gout. Does inhibition of iron absorption by coffee reduce the risk of gout? Let’s find out. Near-iron deficiency-induced remission of gouty arthritis. They took gout patients and maintained their iron stores at the lowest level possible without causing anemia and…gouty attacks markedly diminished in every patient, with effects ranging from a complete remission to a marked reduction of incidence and severity of gouty attacks. Here are the attack rates before and after. So, maybe that’s one reason coffee consumption is associated with lower risk of gout. It blocks some of the iron uptake.

Increasing evidence suggests that iron is also involved in multiple diseases of aging, including Alzheimer’s disease, Parkinson’s disease, and heart disease. In terms of iron and Alzheimer’s, they think it’s iron’s potential to effectively “rust” brain tissue by producing free radicals that may cause neurodegeneration, contributing to Alzheimer’s disease pathology at numerous levels––so much so that there is interest in trying to treat Alzheimer’s disease by targeting iron.

High body iron stores may also be associated with shorter telomeres, which is a biomarker of biological aging. And for those of you thinking, well if I had high iron stores, I’d probably know about it. But only 5 percent of patients with elevated iron report ever being told by a doctor that this was the case.

To prevent too much iron accumulation, regularly drinking tea with meals will do it, found to decrease the amount of bloodletting you have to do for people with a genetic iron overload disease. But you’d want to do the opposite—drink tea only apart from meals—if you were at risk for iron deficiency anemia.

Besides tea and coffee, there are other beverages that can block iron absorption. Peppermint is right up there with black tea. Chocolate milk would do it too. And chamomile blocks iron about in the same range as coffee. So, if your iron stores are high, these are great mealtime choices. If you’re struggling to get enough iron, you wouldn’t want to regularly drink these with meals.

We think it’s the polyphenol phytonutrients. So, what about herbs and spices? They’re packed with polyphenol goodness.

Now, this study was done basically in a test tube, not in real people, but there is this case report of iron deficiency anemia due to high-dose turmeric. A physician treated himself for an osteoarthritis flare with capsules of turmeric extract and he was anemic; couldn’t get his iron up despite taking iron supplements. But two weeks after stopping the turmeric, his blood count and iron levels were all back to normal.

So, on one hand, those presenting to doctor’s offices with iron deficiency anemia should be asked about supplement use; at the same time, the ability of turmeric to glom on to intestinal iron may lead to it being useful in states of iron overload.

Please consider volunteering to help out on the site.

Motion graphics by Avo Media

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

In my videos on tea, I caution not to drink with meals, because it can inhibit the absorption of iron from foods anywhere from 26 to 99 percent, perhaps depending on the brewing time, brand, or how strong it is. What about the inhibition of food iron absorption by coffee?

When I was first looking this up, I ran across this study on the effects of discontinuing coffee intake on the iron status of Guatemalan toddlers. I’m thinking they must be talking about breastfeeding mothers or something, but no, coffee is one of the first liquids given to infants in Guatemala. I did not know that!

Anyway, the inhibition of food iron absorption by coffee. A cup of coffee reduced iron absorption from a hamburger meal by 39 percent, as opposed to a 64 percent decrease with tea. So, not as bad as tea, but still significant blockage. And just like with the tea, the stronger the coffee, the more iron absorption was impeded. In terms of timing, no decrease in iron absorption occurred when coffee was consumed an hour before a meal, but waiting an hour after the meal to drink the coffee didn’t seem to help. This can be probably explained by the fact that it may take up to nearly two hours to clear a meal from the stomach; so, starting an hour in, the coffee can catch up to the food.

Now, you can reverse the effect of tea or coffee by adding orange juice to a meal, or even better an orange, or any source of vitamin C-rich food. The vitamin C boosts iron absorption, which is good for people who are borderline anemic, but for many, the blockage of iron absorption from coffee may actually be a good thing.

Iron is a double-edged sword. On the one hand, iron is an essential element vital for blood production. On the other hand, iron is a potent pro-oxidant. So, maybe the reduced risk of type 2 diabetes associated with coffee consumption is due to the inhibition of iron absorption by coffee.

See, the risk of type 2 diabetes increases with the increase in the amount of ferritin in your blood, which is a measure of your iron stores. So, higher iron stores, higher diabetes risk. It’s the same thing with the risk of gestational diabetes during pregnancy. So, you need to make sure you’re getting enough iron, but not building up too much iron in your body. How do we know it’s cause and effect?

Because if you randomize diabetics to something like old-fashioned bloodletting, but instead of leeches, they just donate blood a couple times to lower their iron stores, and those in the blood donation group had better blood sugar control, better insulin secretion, and less insulin resistance. Iron depletion improves artery dysfunction in type 2 diabetics as well.

It’s the same thing with gout. Does inhibition of iron absorption by coffee reduce the risk of gout? Let’s find out. Near-iron deficiency-induced remission of gouty arthritis. They took gout patients and maintained their iron stores at the lowest level possible without causing anemia and…gouty attacks markedly diminished in every patient, with effects ranging from a complete remission to a marked reduction of incidence and severity of gouty attacks. Here are the attack rates before and after. So, maybe that’s one reason coffee consumption is associated with lower risk of gout. It blocks some of the iron uptake.

Increasing evidence suggests that iron is also involved in multiple diseases of aging, including Alzheimer’s disease, Parkinson’s disease, and heart disease. In terms of iron and Alzheimer’s, they think it’s iron’s potential to effectively “rust” brain tissue by producing free radicals that may cause neurodegeneration, contributing to Alzheimer’s disease pathology at numerous levels––so much so that there is interest in trying to treat Alzheimer’s disease by targeting iron.

High body iron stores may also be associated with shorter telomeres, which is a biomarker of biological aging. And for those of you thinking, well if I had high iron stores, I’d probably know about it. But only 5 percent of patients with elevated iron report ever being told by a doctor that this was the case.

To prevent too much iron accumulation, regularly drinking tea with meals will do it, found to decrease the amount of bloodletting you have to do for people with a genetic iron overload disease. But you’d want to do the opposite—drink tea only apart from meals—if you were at risk for iron deficiency anemia.

Besides tea and coffee, there are other beverages that can block iron absorption. Peppermint is right up there with black tea. Chocolate milk would do it too. And chamomile blocks iron about in the same range as coffee. So, if your iron stores are high, these are great mealtime choices. If you’re struggling to get enough iron, you wouldn’t want to regularly drink these with meals.

We think it’s the polyphenol phytonutrients. So, what about herbs and spices? They’re packed with polyphenol goodness.

Now, this study was done basically in a test tube, not in real people, but there is this case report of iron deficiency anemia due to high-dose turmeric. A physician treated himself for an osteoarthritis flare with capsules of turmeric extract and he was anemic; couldn’t get his iron up despite taking iron supplements. But two weeks after stopping the turmeric, his blood count and iron levels were all back to normal.

So, on one hand, those presenting to doctor’s offices with iron deficiency anemia should be asked about supplement use; at the same time, the ability of turmeric to glom on to intestinal iron may lead to it being useful in states of iron overload.

Please consider volunteering to help out on the site.

Motion graphics by Avo Media

Doctor's Note

For background on iron regulation, see my video Risk Associated with Iron Supplements. 

What about the different types of iron found in food? Check out The Safety of Heme vs. Non-Heme Iron. I also talked about this in my series on plant-based meats. The information on iron starts with What About the Heme in Impossible Burgers?.

For those surprised to hear about coffee’s benefits, see, for example:

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