Can Drinking Tea Reduce Iron Absorption?

Studies have long shown that drinking large amounts of coffee can reduce iron absorption from the foods you eat, but there is also evidence that certain teas can do the same. Research suggests that black tea and green tea, both high in caffeine, may interfere with the absorption. Herbal teas, which have no caffeine, may have little to no effect.

While it may seem to assume that caffeine is the culprit, that's actually not the case.

Compounds That Reduce Iron Absorption

Iron is an essential mineral that you obtain from the foods that you eat. This includes heme iron found in animal products such as meat and fish and non-heme iron derived from plant sources, including nuts.

Iron is mainly absorbed in the first part of the small intestine, called the duodenum, which resides next to the stomach. Compounds in certain foods you eat can bind to iron and prevent absorption, thereby reducing the amount of iron your body receives.

Two of the main compounds involved in this include:

• Polyphenols: A class of compounds found in plants which include flavonoids and tannins
• Phytates: A stored form of phosphorus derived from seeds, nuts, beans, and whole grains

Both of these compounds are essential to good health but can also block the absorption of iron—specifically non-heme iron—if consumed in excess. And, this is especially concerning in that non-heme iron makes up between 70% and 90% of dietary iron.

In rare cases, the overconsumption of polyphenols and phytates can lead to iron deficiency and iron deficiency anemia. People most affected by this are pregnant people, vegans, and athletes on a restricted diet who tend to have lower iron stores in their bodies.

Why Coffee and Tea Are a Problem

Numerous studies have shown that coffee and tea—both of which are high in caffeine—may significantly decrease iron absorption.

One study from Korea published in 2023 reported that drinking three cups of coffee a day reduces iron absorption by 8.4% in males and 18.8% in females. With respect to non-heme iron specifically, the high consumption of coffee reduced it by as much as 40%.

The high consumption of black tea also appears to have the same effect. A 2024 study from Pakistan reported that the high consumption of black tea, common in Pakistani culture, doubled the risk of iron-deficiency anemia compared to non-tea drinkers.

In both instances, the culprit impeding iron absorption is tannin. Tannins are potent polyphenol compounds that give tea, coffee, and red wine their dry and puckery taste.

Tannin Content

With coffee, tannin concentration hovers at around 5% but can increase or decrease based on the level of roasting. Light-roasted coffee generally has more tannins than medium or dark roast because the process of roasting the beans breaks down certain compounds.

Tea appears to have even more, averaging around 15% for black tea and 8% for oolong tea (a type of white tea).

With respect to green tea, the evidence is split as to whether it can affect iron absorption. Some studies suggest a connection, while others do not. This may be due to the fact that green tea has far less tannin than either coffee, black tea, or white tea, averaging only around 2.7%.

What About Herbal Tea?

Black, white, and green tea all come from the leaves of the Camellia sinensis plant. The leaves and buds of C. sinesis are a rich source of tannin, the concentration of which can increase with a process known as oxidation.

Tea oxidation involves exposing the leaves and buds to the air to dry and darken them, contributing to the flavor, aroma, and strength of different teas. Green tea is the type that does not undergo oxidation, while white and black teas are semi-oxidized and fully-oxidized, respectively.

While herbal teas are not made from C. sinesis, that doesn't mean that they are without tannins. With that said, they have less tannin than C. sinesis and don't undergo the same oxidation process to bring out the characteristic bitter notes.

Tannin levels between herbal teas can vary considerably. Those that have a naturally bitter or astringent taste have higher tannin content than those that do not.

These include:

• Hibiscus
• Cinnamon
• Peppermint
• Raspberry
• Rooibos
• Rosehip
• Yerba mate

Even so, there is little research as to whether these teas are more or less impactful on iron absorption than coffee or black tea.

Consumption Tips

Current research suggests that iron absorption may be significantly reduced when coffee or black tea is consumed in excess. Low or moderate consumption may have little or no effect and rarely leads to iron deficiency anemia (unless a person already has risk factors).

If you are at risk of iron deficiency, there are certain you can do to reduce the risk if you are a coffee or tea drinker:

• Choose green tea over white or black tea.
• Choose darker roasts over light roasts for coffee.
• Don't drink coffee or tea with meals. Studies have shown that waiting at least one hour after meals can erase their effect on iron absorption.
• Try drinking herbal teas that are low in tannin, including rooibos and chamomile.
  

Summary

Tannins in tea may inhibit iron absorption, especially non-heme iron found in plant-based foods. These polyphenol compounds bind to iron and prevent them from passing through the small intestine and into the bloodstream.

Black tea and white tea, made from the leaves and buds of the Camelia sinesis plant, appear to have the greatest impact, while green tea and herbal teas tend to have a lower impact. Even so, iron deficiency is rare unless you drink large amounts of coffee or black tea and/or have underlying risk factors for iron deficiency.