Why reheating tea could be doing you more harm than good
A boiling vessel with tea.
For most people, tea is more than just a beverage; it’s a comforting ritual, a way to start the day, or a pause for relaxation. In the hustle of daily life, several people are guilty of letting their tea grow cold and then reheating it for a quick, comforting sip.
However, doctors and multiple research suggest that this seemingly harmless habit could compromise the beverage’s quality and consequently the health of those consuming it.
While it may seem harmless, reheating tea can significantly alter its nutritional value, taste, and even safety.
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The chemical breakdown of your brew
Tea is rich in polyphenols and bioactive compounds responsible for its antioxidant properties. These include catechins, theaflavins, and thearubigins, compounds that have been linked to reduced inflammation, improved heart health, and better metabolic function.
However, reheating tea can degrade these compounds, diminishing their health benefits.
“When tea is subjected to repeated heating, its polyphenols lose their structural integrity. Reheating destroys their antioxidant properties, leaving the tea nutritionally compromised,” said Hyderabad-based neurologist Dr Sudhir Kumar. Catechins, abundant in green tea, are particularly sensitive to heat.
Reheating also alters the tea’s flavour profile, as volatile compounds responsible for its aroma break down. Additionally, vitamins like vitamin C and amino acids like L-theanine degrade with heat, making reheated tea far less beneficial than freshly brewed tea.
A breeding ground for bacteria
“If tea sits out at room temperature for more than four hours, it becomes a breeding ground for bacteria. The warm, moist environment is ideal for bacterial growth, increasing the risk of gastrointestinal infections,” said Dr Kumar.
Certain bacteria, such as Bacillus cereus and Salmonella, can survive and thrive in brewed tea. While tea contains some natural antibacterial properties, it is not immune to contamination over time.
Reheating tea to high temperatures may not kill all bacteria, especially heat-resistant pathogens that can survive boiling. These bacteria can form spores that withstand reheating, posing a risk of gastrointestinal infections.
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The bitter truth about tannins
Tannins, naturally occurring compounds in tea, contribute to its astringency and colour. While tannins have antioxidant properties, their increased release during reheating can negatively affect the tea’s taste and nutritional value.
When tea is reheated, it extracts more tannins from the leaves, making it taste bitter and unpleasant. This is particularly noticeable in green and white teas, which have delicate flavour profiles.
Tannins bind to dietary iron, especially non-heme iron found in plant-based foods, reducing its bioavailability. For individuals at risk of iron deficiency or those following vegetarian diets, reheated tea can further hinder iron absorption, affecting overall nutrition.
“Reheating tea causes an increased release of tannins from the tea leaves, which significantly alters its taste and flavour, often making it more bitter. Beyond the impact on flavour, tannins can also interfere with the body’s ability to absorb iron. Specifically, tannins bind to non-heme iron (commonly found in plant-based foods), reducing its bioavailability,” said Dr Kumar.
This can be particularly concerning for individuals at risk of iron deficiency or those following vegetarian or vegan diets,”
Caffeine concerns
Caffeine, a natural stimulant in tea, can have both positive and negative effects. “Reheating tea increases the extraction of caffeine, which can have implications for those sensitive to it,” said Dr Kumar.
Reheating can lead to higher levels of caffeine being extracted from the tea leaves. This means that a reheated cup of tea may contain more caffeine than freshly brewed tea, potentially causing side effects.
According to Dr Kumar for individuals sensitive to caffeine, this can lead to:
- Sleep disturbances: Caffeine has a long half-life, staying in the body for hours and disrupting sleep patterns.
- Acidity and discomfort: Caffeine stimulates gastric acid secretion, which can worsen symptoms for those with sensitive stomachs or acid reflux.
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A cancer risk?
“Drinking very hot tea, particularly at temperatures above 65°C, has been linked to an increased risk of oesophagal cancer. The World Health Organisation (WHO) classifies beverages consumed at such high temperatures as “possibly carcinogenic.”,” said Dr Kumar.
Tissue Damage: Consuming very hot liquids can damage the delicate lining of the oesophagus. Over time, this damage may lead to chronic inflammation, increasing the risk of oesophagal cancer.
Amplified Risks: The danger is heightened when combined with other risk factors like smoking and alcohol consumption.
Studies show that individuals who regularly drink tea above 65°C are 1.7 times more likely to develop oesophagal cancer compared to those who consume cooler beverages.
Brewing for optimal enjoyment and health
To maximise the benefits and enjoyment of your tea, Dr Kumar suggests it’s best to:
- Brew fresh: Enjoy your tea promptly after brewing for the best flavour and maximum health benefits.
- Mind the temperature: Avoid drinking tea that is excessively hot. Aim for a comfortable temperature below 65°C.
- Refrigerate leftovers: If you have leftover tea, store it in the refrigerator to prevent bacterial growth. Reheat gently and only once if necessary.
Why you should NOT reheat your tea and drink?
We all enjoy a hot cup of tea. Sometimes, if one is unable to have tea on time, and it gets cold, tea is often reheated and served. But this practice is unhealthy. Here are the 5 reasons:
1/n— Dr Sudhir Kumar MD DM (@hyderabaddoctor) January 26, 2025
(Edited by Muhammed Fazil.)
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