Is it unhealthy to steep green tea too long?

December 17, 2025 •

3 min read

A study showed that over-steeping green tea for hours can actually decrease its antioxidant activity. This raises the question: is it unhealthy to steep green tea too long? Beyond just a bitter taste, letting your tea brew for excessive periods can impact its chemical composition and your body.

Quick Summary

Oversteeping green tea can increase its tannin and caffeine content, leading to digestive issues and hindering iron absorption, while compromising flavor and antioxidant benefits.

Key Points

Bitter Flavor: Oversteeping releases a high concentration of tannins, resulting in an unpleasantly bitter and astringent taste.
Digestive Issues: Excessive tannins can irritate the stomach lining, potentially causing nausea or acid reflux, especially on an empty stomach.
Iron Absorption: The high tannin content can hinder the body's ability to absorb iron from plant-based foods, which is a concern for those with iron deficiency.
Reduced Antioxidants: Prolonged steeping in hot water can degrade the very antioxidants that make green tea so healthy.
Increased Caffeine: The longer the tea steeps, the more caffeine is released, which can cause restlessness or headaches for caffeine-sensitive individuals.
Optimal Brewing: Using a lower water temperature (160-185°F) and a short steeping time (2-3 minutes) prevents bitterness and preserves flavor and nutrients.

The Chemical Shift: What Happens When You Oversteep?

When green tea leaves are steeped for an extended time or in water that is too hot, the chemical makeup of the resulting beverage changes significantly. The delicate balance of compounds, which gives green tea its unique flavor and health benefits, is thrown off. Primarily, this is due to the excessive extraction of two key compounds: tannins and caffeine.

The Impact of Excessive Tannins

Tea contains naturally occurring polyphenols known as tannins, which contribute to its color, flavor, and some of its antioxidant properties. However, when green tea is steeped for too long, a high concentration of tannins is released, leading to several negative effects.

Bitter, Astringent Taste: The most immediate and noticeable effect is the unpleasant, bitter taste and dry, puckering sensation in the mouth. The delicate, grassy, or nutty flavor notes are completely overpowered by the strong, astringent tannins.
Stomach Irritation: A high dose of tannins can irritate the stomach lining, potentially leading to digestive issues such as nausea, constipation, or acid reflux, especially if consumed on an empty stomach.
Reduced Iron Absorption: One of the most significant concerns is the inhibitory effect of tannins on non-heme iron absorption. The tannins can bind with iron from plant-based foods, making it harder for the body to absorb it. This is particularly relevant for individuals with or prone to anemia. Drinking tea between meals rather than with them can help mitigate this effect.

The Change in Antioxidant and Caffeine Levels

While some might assume a longer steep extracts more antioxidants, the reality is more nuanced. While initial studies showed an increase, oversteeping for prolonged periods (e.g., several hours) can actually decrease the overall antioxidant activity as the compounds degrade. Furthermore, the amount of caffeine released into your cup increases with steeping time. For those sensitive to caffeine, this could lead to jitters, restlessness, headaches, or disrupted sleep patterns.

The Brewing Sweet Spot: Why Time and Temperature Matter

Brewing green tea is a science of balance. Proper preparation ensures that the beneficial compounds are extracted while minimizing the release of harsh-tasting tannins and preserving the tea's delicate flavor profile. Key factors include:

Water Temperature: Unlike black tea, green tea should not be made with boiling water. High temperatures scorch the delicate leaves and cause a rapid release of bitter tannins. The ideal range is typically between 160°F and 185°F (71°C to 85°C).
Steeping Time: The recommended steeping time for most green teas is a short 2 to 3 minutes. Some delicate varieties may require even less. This brief period is sufficient to extract the desired flavor and health-promoting compounds without releasing too many tannins.

Properly Steeped vs. Oversteeped Green Tea


Feature	Properly Steeped Green Tea	Oversteeped Green Tea
Flavor Profile	Grassy, vegetal, sometimes nutty or floral, with a smooth finish.	Intensely bitter, harsh, and astringent, overpowering all other flavor notes.
Color	A light, vibrant yellow-green hue.	Darker, brownish, and murky due to oxidation and heavy tannin extraction.
Tannin Levels	Balanced extraction of tannins contributes to a pleasant mouthfeel.	High concentration of tannins leads to an unpleasant, dry sensation.
Antioxidant Activity	High antioxidant activity, maximizing health benefits.	Can be reduced by prolonged exposure to hot water.
Caffeine Content	Moderate, providing a gentle boost of energy.	Higher, which can be a concern for sensitive individuals.
Health Impact	Rich in antioxidants and potential health benefits.	Can cause stomach upset and inhibit iron absorption.

Conclusion: Moderation and Technique are Key

While oversteeping a single cup of green tea is unlikely to cause serious harm, it does significantly degrade the quality of your brew and can lead to minor digestive discomfort and inhibited iron absorption. The primary health risks are associated with consuming excessive amounts of very strong, oversteeped tea or high-dose green tea extracts. The best way to enjoy green tea's numerous benefits—from its antioxidants to its cognitive-enhancing properties—is to master the art of proper brewing. By paying attention to the correct water temperature and steeping time, you can create a perfectly balanced, flavorful, and healthy cup every time.

For more information on the side effects of excessive green tea consumption, see this resource:.

Frequently Asked Questions

While it is unlikely to cause serious illness from a single cup, oversteeped green tea can cause stomach upset, nausea, or acid reflux, especially if consumed on an empty stomach due to the high concentration of tannins.

The bitterness in oversteeped green tea comes from the excessive release of tannins, a type of polyphenol. These compounds are responsible for the tea's astringent, dry-mouthed sensation.

For most varieties, the ideal steeping time is 2 to 3 minutes in water heated to between 160°F and 185°F. Steeping for too long or using boiling water will result in a bitter taste.

In prolonged periods of oversteeping (e.g., several hours), the beneficial antioxidant compounds can actually degrade and lose their potency. A normal, brief steep is best for preserving antioxidant activity.

Yes, the longer you steep green tea, the more caffeine is released into the water. This can result in a more stimulating effect, which may be undesirable for those sensitive to caffeine.

Yes, the high concentration of tannins in oversteeped tea can inhibit the body's absorption of non-heme iron, which is found in plant-based foods. It is recommended to drink green tea between meals rather than with them to avoid this.

You can try to dilute the oversteeped tea by adding more water, which may reduce the bitterness. However, the best way to avoid a poor-tasting cup is to prevent oversteeping in the first place.