What deficiency does tea cause?

October 13, 2025 •

4 min read

Research indicates that tea consumption can significantly reduce the body's absorption of iron from plant-based foods, with some studies showing an inhibition of up to 60% when drunk with a meal. This effect is primarily due to compounds called tannins, not the tea itself, and disproportionately impacts those with existing low iron stores or specific dietary habits.

Quick Summary

Excessive tea drinking can lead to iron deficiency, especially in individuals following plant-based diets, due to compounds called tannins. Understanding this mechanism and timing consumption can prevent this potential issue.

Key Points

Iron Malabsorption: The primary deficiency concern is reduced iron absorption from plant-based foods, caused by tannins in tea.
High-Risk Groups: Vegetarians, vegans, and those with existing low iron stores are most susceptible to iron deficiency from high tea intake.
Timing is Crucial: Avoid drinking tea for at least one hour before and after meals to minimize its effect on iron absorption.
Vitamin C as an Antidote: Pairing iron-rich plant foods with Vitamin C can counteract the inhibitory effect of tannins on absorption.
Not All Teas Are Equal: Black tea has the highest tannin content, while green tea has less, and many herbal teas have minimal impact on mineral absorption.
Bone Health Unaffected: The idea that tea causes calcium loss and osteoporosis is largely a myth; modern research shows no negative impact and may even suggest benefits for bone density.
Moderation is Safe: For most healthy individuals with a balanced diet, moderate tea consumption does not lead to significant nutritional deficiencies.

Tea is one of the most widely consumed beverages globally, cherished for its flavor, aroma, and numerous health benefits derived from antioxidants. However, beneath its celebrated status, lies a lesser-known nutritional interaction that can have a notable impact on the body's ability to absorb certain minerals. While moderate intake poses little risk for healthy individuals, excessive consumption, particularly around mealtimes, can interfere with nutrient absorption, most notably leading to an iron deficiency. This issue arises not from the tea inherently lacking nutrients, but from its anti-nutritional compounds interfering with the absorption of nutrients from other foods.

The Primary Deficiency: Iron Malabsorption

The most significant nutritional concern associated with tea consumption is its impact on iron absorption, a well-documented phenomenon. The primary culprits are tannins, a class of polyphenols found in various plants, including the Camellia sinensis plant from which black, green, and oolong teas are derived.

How tannins work: Tannins are chelators, meaning they can bind to certain minerals in the digestive tract. When tannins bind to iron, they form a complex that is insoluble and difficult for the body to absorb through the intestinal lining. This renders the iron effectively unavailable for use by the body. Research has shown that a single cup of tea can reduce iron absorption from a meal by a significant margin.
Non-heme vs. Heme Iron: The inhibitory effect of tannins is far more pronounced on non-heme iron, which is the type found in plant-based sources like spinach, beans, and fortified grains. Heme iron, found in animal products such as meat, poultry, and fish, is absorbed much more efficiently and is largely unaffected by tannins. This difference explains why vegetarians, vegans, and those with limited meat intake are at a much higher risk of developing an iron deficiency from tea consumption.

Who Is at Highest Risk?

While tea does not cause an iron deficiency in everyone, certain groups are more susceptible due to their dietary patterns or physiological needs.

Vegetarians and vegans: Their diets rely on non-heme iron sources, which are most vulnerable to tannin interference. They should be particularly mindful of when and how they consume tea.
Individuals with low iron stores: People already diagnosed with iron-deficiency anemia or those with low ferritin levels should exercise caution. Consuming tea during oral iron supplementation can also compromise its effectiveness.
Pregnant women and women with heavy menstruation: These groups have a higher demand for iron. A review of studies suggests that high caffeine exposure during pregnancy may increase complication risks, though data is mixed.
Children and adolescents: Some studies have identified tea consumption as a potential risk factor for anemia in schoolchildren, particularly in regions where tea drinking with meals is common.

Mitigating the Risk of Nutrient Deficiencies

Fortunately, tea drinkers don't have to give up their favorite beverage to protect their iron levels. Simple strategies can significantly reduce the risk of impaired absorption.

Timing is key: The most effective way to prevent interference is to separate tea consumption from mealtimes. Experts recommend waiting at least one hour after an iron-rich meal to have a cup of tea. Similarly, avoid drinking tea for an hour before a meal.
Enhance absorption with vitamin C: Vitamin C is a powerful enhancer of non-heme iron absorption. Combining iron-rich plant foods with sources of vitamin C (like citrus fruits, bell peppers, or berries) can help counteract the effects of tannins.
Choose lower-tannin teas: The amount of tannins varies by tea type and preparation. Black tea generally has the highest concentration, while green tea has less, and herbal infusions typically contain very low levels. For those at higher risk, opting for low-tannin herbal teas like chamomile or rooibos is a safer option.
Add milk: The proteins in milk can bind to tannins, neutralizing their effect on iron absorption. This is a common practice in many cultures and serves a functional purpose.
Mind your brewing time: A shorter steeping time for black or green tea results in a lower tannin content in the final brew.

Potential Impact on Other Nutrients

While iron is the most commonly cited mineral, tannins in tea can also affect the absorption of other nutrients. Early research, though less definitive for tea than for coffee, suggests some potential influence on calcium and vitamin B1.

Calcium and bone health: The idea that tea leads to calcium deficiency and osteoporosis is a misconception. Research, including a recent Mendelian randomization study, indicates that tea consumption does not negatively impact bone density and may even have protective effects due to other beneficial compounds. However, some very early studies and anecdotal evidence pointed to caffeine potentially increasing urinary calcium excretion, but modern comprehensive analysis debunks this.
Vitamin B1 (Thiamine): Tea has been associated with a potential deficiency of thiamine, a vitamin important for energy metabolism and brain health. However, this is primarily a concern with long-term, high consumption and is less common than issues related to iron.

How Different Teas Compare


Tea Type	Tannin Level	Impact on Non-Heme Iron Absorption	Recommended for At-Risk Individuals?
Black Tea	High	Significant reduction in absorption	No, especially with meals
Green Tea	Moderate to Low	Moderate reduction in absorption	Okay in moderation, between meals
Oolong Tea	Moderate	Moderate reduction in absorption	Okay in moderation, between meals
Herbal Tea (e.g., Rooibos, Chamomile)	Very Low	Minimal to no impact on absorption	Yes, good alternative

Conclusion

Ultimately, enjoying tea is a healthy habit for most people, and the risk of a nutritional deficiency is only significant under certain circumstances. The key takeaway is to be mindful of timing, especially if you fall into a high-risk group like vegans or those with a history of anemia. By implementing simple strategies, such as drinking tea between meals and pairing iron-rich foods with vitamin C, you can enjoy the many benefits of tea without compromising your nutritional health. When in doubt, or if you have concerns about your iron levels, consult with a healthcare professional to determine the best approach for your individual needs.

Frequently Asked Questions

Yes, excessive consumption of black tea, especially when consumed with meals, can contribute to iron-deficiency anemia by inhibiting the absorption of non-heme iron from plant-based foods.

For those concerned about iron absorption, opting for herbal teas like rooibos or chamomile is a good strategy. These teas typically contain very low levels of tannins, which are the compounds that interfere with iron absorption.

Yes, the proteins in milk can bind with the tannins in tea, neutralizing their effect on iron absorption. This is a simple and effective method to minimize the risk of deficiency.

To be safe, wait at least one hour after eating an iron-rich meal before drinking tea. This time interval allows for better iron absorption before the tannins from the tea are introduced.

Yes, green tea contains tannins, although in lower concentrations than black tea. Therefore, it can also inhibit non-heme iron absorption, especially when consumed with meals. The same precautions regarding timing apply.

No, despite some past theories, modern research, including meta-analyses and Mendelian randomization studies, has shown that moderate tea consumption does not cause calcium loss and may even benefit bone mineral density.

The primary compounds are tannins, a type of polyphenol. Tannins act as chelators, binding to minerals like iron in the digestive tract and preventing their absorption by the body.