Does milk reduce the benefits of black tea? The science of your daily cuppa

December 25, 2025 •

4 min read

While adding a splash of milk to black tea is a beloved tradition in many parts of the world, a scientific debate has questioned whether this practice neutralizes the tea's benefits. Conflicting research has made it unclear whether milk reduces the benefits of black tea or merely changes their absorption, leaving many tea drinkers pondering their brewing habits.

Quick Summary

Adding milk to black tea may slightly alter its antioxidant activity due to protein interactions, but evidence is contradictory, and total health benefits are likely not completely erased.

Key Points

Conflicting Evidence: Studies on milk affecting black tea benefits are contradictory, with some showing interference and others showing little to no effect.
Casein-Polyphenol Binding: The primary theory is that milk protein casein can bind to the antioxidant polyphenols in tea, making them less bioavailable.
Reduced Vascular Benefits: One study found that adding milk to black tea blunted the tea's positive effect on blood vessel function.
Not a Total Loss: Even if some antioxidants are affected, the tea retains many benefits, and the milk adds its own nutrients like calcium and protein.
Maximizing Antioxidants: For the highest concentration of bioavailable antioxidants, drinking black tea without milk is the most certain method.
Brewing Method Matters: Factors like infusion time can influence the number of polyphenols extracted, possibly affecting how much milk interferes.
Consider Your Priorities: If you prioritize taste and added nutrients over maximizing antioxidant intake, adding milk is perfectly acceptable.

The Science Behind Black Tea's Benefits

Black tea, derived from the leaves of the Camellia sinensis plant, is rich in a group of plant compounds known as polyphenols, which act as powerful antioxidants. These compounds help neutralize harmful free radicals in the body, which are linked to chronic diseases like heart disease and cancer. The primary polyphenols found in black tea are theaflavins and thearubigins, which are formed during the oxidation process that gives black tea its characteristic dark color and flavor. L-theanine, an amino acid also found in black tea, provides a calming effect and can improve cognitive function.

The Impact of Milk: The Casein Connection

The central argument that milk can reduce the benefits of black tea revolves around the interaction between milk proteins and the tea's polyphenols. The primary protein in milk, casein, has been shown in some in vitro (test tube) studies and smaller human trials to bind with polyphenols. When this binding occurs, the polyphenols become less available for absorption by the body. A notable study from 2007 on women measured blood flow and found that while plain black tea significantly improved blood vessel function, black tea with milk did not, suggesting the casein had blocked the beneficial effect.

The Conflicting Evidence: Not a Clear-Cut Case

Despite the findings suggesting a negative interaction, the scientific picture is far from definitive. Several other studies have produced contradictory results, finding no significant effect of milk on the absorption of antioxidants in human subjects. Researchers attribute these conflicting outcomes to a variety of factors, including the brewing method, the type and amount of milk used, and the methodology of the different studies. Some evidence even suggests that longer brewing times might allow for greater antioxidant absorption, regardless of milk's presence.

Furthermore, it's crucial to distinguish between a minor reduction in antioxidant capacity and the complete elimination of health benefits. Even if milk binds with some polyphenols, the remaining antioxidants in the tea, combined with the nutrients present in the milk itself (like calcium and protein), still offer nutritional value. An interesting review points out that while some studies show a decrease in total antioxidant capacity, this doesn't directly translate to a loss of all health benefits in the human body.

Comparison: Black Tea vs. Milk Tea


Feature	Plain Black Tea	Black Tea with Milk
Antioxidant Absorption	Optimal, as polyphenols are fully bioavailable.	Potentially reduced, as casein may bind with polyphenols.
Heart Health	Strong evidence of benefits, including improved vascular function.	Conflicting evidence; some studies show blunted vascular effects.
Nutritional Value	Provides antioxidants and hydration with very few calories.	Adds calcium, vitamin D, and protein from milk, but also calories.
Taste Profile	Bold, slightly bitter, and astringent.	Smoother, creamier, and milder taste.
Potential Downsides	Can be too strong for some palates; caffeine content varies.	Added calories and sugar if sweeteners are included.

Maximizing Your Black Tea's Potential

If your primary goal is to maximize the antioxidant benefits of your tea, particularly for cardiovascular health, here are some tips:

Brew longer: A longer infusion time can release more phenolic compounds into the water, potentially overriding any effects of milk.
Consider low-protein milk alternatives: If you want a creamy texture without the casein, some alternative milks might be a better choice. However, some plant-based milks may also interact with polyphenols.
Use high-quality loose-leaf tea: Some analyses suggest that using tea bags can release fewer antioxidants compared to loose-leaf tea.
Time your consumption: For those concerned about iron absorption, avoid drinking black tea immediately after an iron-rich meal, whether with or without milk, as tannins can interfere.

Conclusion

Ultimately, whether milk reduces the benefits of black tea depends on your individual health goals and how you define 'benefits.' For maximum antioxidant bioavailability, drinking black tea without milk is the most straightforward choice based on current research. However, the evidence is not universally conclusive, and adding a small amount of milk may only have a minor impact on overall health effects. If you enjoy the creamy taste of tea with milk, the pleasure and nutritional additions may outweigh the theoretical reduction in antioxidant activity. As with any dietary question, balance and moderation are key. The important takeaway is that enjoying black tea, with or without milk, is part of a healthy diet, particularly when compared to less healthy beverage options.

For further reading on the complex interaction of milk and tea, consult this comprehensive review: https://www.researchgate.net/publication/282120147_Addition_of_milk_to_tea_infusions-helpful_or_harmful_Evidence_from_in_vitro_and_in_vivo_studies_on_antioxidantproperties-_A_review

Frequently Asked Questions

Some studies suggest milk reduces the benefits because the protein casein binds with the antioxidant polyphenols in tea, which can reduce their absorption and activity in the body.

No, adding milk does not completely destroy all health benefits. While it may slightly affect antioxidant absorption, the tea still provides other beneficial compounds. Milk also adds its own nutritional value, such as calcium and protein.

Some research indicates that adding milk, regardless of its fat content (skim or whole), can reduce the total antioxidant capacity of black tea infusions, though results vary. Some findings suggest skim milk might have a greater negative effect on antioxidant capacity than whole milk.

Yes, some studies suggest that longer brewing times may lead to better absorption of tea's antioxidants, potentially lessening the impact of adding milk.

For maximizing antioxidant intake and potential heart health benefits, plain black tea is generally considered the healthier option. However, milk tea offers additional nutrients from the milk, and the healthiest choice depends on your specific nutritional priorities.

Soy and other plant-based milks, which contain different protein types, have also been shown to potentially interfere with tea antioxidants, though the exact effect varies.

If you prioritize taste and enjoy your tea with milk, there is no need to stop based on inconclusive evidence. If your goal is to maximize antioxidant benefits, consider drinking it black or using less milk.