Does Tea Destroy Protein in Milk? The Scientific Truth

January 13, 2026 •

4 min read

Adding milk to tea has been a common practice for centuries, but many people question its nutritional impact. The concern often revolves around whether tea destroys protein in milk, nullifying the health benefits of both ingredients. This article delves into the chemical and biological processes involved to separate fact from fiction regarding this popular beverage combination.

Quick Summary

This article explores the scientific facts about whether tea destroys protein in milk. It explains the interaction between tea's tannins and milk's casein, how this binding affects nutrient availability, and whether it has any significant impact on the protein's overall nutritional value.

Key Points

Protein is not destroyed: Tea's tannins bind to milk's casein, a chemical interaction that does not destroy the protein itself.
Antioxidant binding occurs: The binding of tannins to protein may reduce the bioavailability and activity of tea's antioxidants, although studies have shown conflicting results.
Nutritional impact is minor for most: For individuals on a balanced diet, the impact on overall protein digestion is negligible.
Flavor is affected: The tannin-protein interaction reduces the astringency of tea, leading to a smoother, creamier taste.
Type of tea and milk matters: The specific effects can vary based on the type of tea, milk, and preparation method, highlighting the complexity of the interaction.
Consider milk alternatives: If maximizing antioxidant intake is a priority, low-protein milk alternatives like almond milk are a viable option.

The Science Behind Tea and Milk Interaction

The belief that tea destroys protein in milk is a common misconception, primarily stemming from a misunderstanding of how the two substances interact. While a chemical reaction does occur, it's not a destructive one in the typical sense. The primary culprits behind this interaction are tea's tannins, a class of polyphenolic compounds, and milk's casein proteins.

The Role of Tannins and Casein

Tannins are naturally occurring compounds in tea leaves that give tea its characteristic astringent flavor and dark color. Casein is the main protein found in milk. When tea and milk are mixed, the tannins bind to the casein proteins, forming insoluble complexes. This binding process is a natural chemical interaction, not a destruction of the protein itself.

Here is a step-by-step breakdown:

Brewing tea: Hot water extracts tannins and other compounds from the tea leaves.
Adding milk: Casein proteins are introduced into the solution.
Binding process: Tannins and casein bind together through non-covalent interactions like hydrogen bonds.
Reduced astringency: This binding makes the tannins less available to interact with taste receptors, resulting in a smoother, less bitter taste.
No protein destruction: The protein is not destroyed, but rather its structure is modified by the binding. The overall nutritional value of the protein is largely preserved.

The Impact on Nutritional Availability

One of the main areas of scientific debate is whether the tannin-protein complexes formed affect the bioavailability of the nutrients. Several studies have explored this topic with conflicting results.

Impact on Antioxidant Activity

Some studies have indicated that the binding of tannins to casein can inhibit the antioxidant effects of tea's flavonoids. One study observed that adding skim milk to black tea prevented the increase in blood flow that was seen when drinking plain tea. However, other studies found no significant difference in antioxidant levels in the blood plasma of people who consumed tea with or without milk. The discrepancies in findings can be attributed to the type of tea used, the amount of milk added, and the brewing method.

Impact on Protein and Iron Digestion

While the binding can impact the absorption of certain compounds, the effect on protein digestion is minimal for most people. A study on the digestibility of egg protein found that black tea significantly reduced its digestibility, but the effect was likely different when milk was involved. For individuals with a protein-adequate diet, the small effect is insignificant. There is a more significant concern for iron absorption, as tannins are known to bind with iron, particularly plant-based (non-heme) iron, and inhibit its absorption.

Scientific Consensus and Conflicting Research

The scientific community does not have a single, definitive consensus on the complete effects of adding milk to tea. The research has yielded varied results, emphasizing the complexity of food chemistry and human physiology.

Comparison Table: Tea with Milk vs. Tea without Milk


Feature	Tea with Milk	Tea without Milk
Protein	Protein remains intact but binds with tannins.	Protein is absent.
Tannin Effects	Tannins bind to milk protein, reducing astringency.	Tannins are more bioavailable, leading to a stronger, more astringent taste.
Antioxidant Absorption	Some studies show reduced antioxidant activity; others report minimal impact.	Antioxidants are fully available for absorption.
Mouthfeel	Creamier, smoother texture.	Lighter, thinner consistency.
Stomach Effects	Milk proteins can neutralize some stomach acidity.	Can potentially cause stomach irritation or nausea on an empty stomach due to tannins.

What the Research Tells Us

Numerous studies have explored the interaction between tea and milk, highlighting the nuances involved. A review published in the journal Nutrients investigated the effect of adding milk protein to green tea on diet-induced thermogenesis. It found that milk protein inhibited the metabolic boosting effect of green tea, suggesting that casein can interfere with the beneficial properties of certain teas. Conversely, a study reviewed by Healthline showed that adding milk to black tea did not inhibit the increase of antioxidant flavonoids in the bloodstream. This contradictory evidence underscores that the effects vary depending on the type of tea, brewing method, and other factors.

For most people who enjoy a cup of milk tea, the binding of tannins and protein is a minor issue. The body still absorbs the protein from the milk, and the nutritional intake from a standard cup of tea and milk is not significantly altered. Those concerned about maximizing antioxidant benefits can simply drink plain tea or consider adding milk alternatives with low protein content, such as almond milk. The binding phenomenon, however, is a fascinating area of study in food science. For a more detailed look into this, consider reading a review on the topic published in ResearchGate.

Conclusion

In summary, the notion that tea destroys protein in milk is a myth. The two substances undergo a chemical interaction where tannins from the tea bind to casein proteins from the milk. This binding process does not destroy the protein but does affect the bioavailability of certain compounds, particularly the antioxidants in tea. While some studies suggest a reduction in the tea's antioxidant benefits, others show no significant impact. For the average consumer, the nutritional effect is negligible, and the milk's protein content remains a valid source of nutrients like protein and calcium. Enjoying milk tea is a matter of personal preference, and understanding the science behind it can help put unfounded nutritional worries to rest.

Frequently Asked Questions

No, it is not unhealthy to drink tea with milk in moderation. While some evidence suggests the milk proteins can slightly reduce the activity of tea's antioxidants, the overall health benefits from both tea and milk are still present.

The research on this is conflicting. Some studies show that adding milk may reduce the absorption or bioavailability of tea's antioxidants (flavonoids), while others find no significant difference. Any reduction is likely minimal for the average consumer.

Curdling can occur due to the presence of acids in tea (tannic acid). This is more likely to happen if the tea is very concentrated, the milk is slightly spoiled, or the brewing process is done incorrectly, causing the milk proteins to destabilize.

The binding of tannins to protein can slightly hinder protein digestion, but the effect is generally minimal for people with adequate protein intake. There is a more notable effect on iron absorption, as tannins can interfere with its uptake.

Yes, you can still get the nutritional benefits from milk. The protein and calcium in milk are not destroyed by the tea; they are simply bound to the tea's tannins. This binding does not prevent your body from absorbing these nutrients.

If you are concerned about maximizing antioxidant benefits, you might consider drinking plain tea. If you still prefer milk tea, brew your tea for a longer period before adding a small amount of milk to help maintain some antioxidant absorption.

The interaction primarily occurs with teas containing tannins, such as black and green teas. Black tea typically has higher levels of tannins than green tea. The specific effects depend on the concentration of these compounds.