Tea is one of the world’s most beloved beverages. The most popular varieties are green, black, and oolong — all of which are made from the leaves of the Camellia sinensis plant (1). Few things are as satisfying or soothing as drinking a hot cup of tea, but the merits of this beverage don’t stop there.
Tea has been used for its healing properties in Traditional medicine for centuries. Moreover, modern research suggests that plant compounds in tea may play a role in reducing your risk of chronic conditions, such as cancer, obesity, diabetes, and heart disease (1). Though moderate tea consumption is a very healthy choice for most people, exceeding 3–4 cups (710–950 ml) per day could have some negative side effects.
Here are 9 possible side effects of drinking too much tea.
1. Reduced iron absorption
Tea is a rich source of a class of compounds called tannins. Tannins can bind to iron in certain foods, rendering it unavailable for absorption in your digestive tract (2). Iron deficiency is one of the most common nutrient deficiencies in the world, and if you have low iron levels, excessive tea intake may exacerbate your condition.
Research suggests that tea tannins are more likely to hinder the absorption of iron from plant sources than from animal-based foods. Thus, if you follow a strict vegan or vegetarian diet, you may want to pay extra close attention to how much tea you consume (2). The exact amount of tannins in tea can vary considerably depending on the type and how it’s prepared. That said, limiting your intake to 3 or fewer cups (710 ml) per day is likely a safe range for most people (2).
If you have low iron but still enjoy drinking tea, consider having it between meals as an extra precaution. Doing so will make it less likely to affect your body’s ability to absorb iron from your food at mealtimes.
Tannins found in tea can bind to iron in plant-based foods, reducing the amount that you’re able to absorb in your digestive tract. If you have low iron, drink tea between meals.
2. Increased anxiety, stress, and restlessness
Tea leaves naturally contain caffeine. Overconsuming caffeine from tea, or any other source, may contribute to feelings of anxiety, stress, and restlessness (3). An average cup (240 ml) of tea contains about 11–61 mg of caffeine, depending on the variety and brewing method (4, 5). Black teas tend to contain more caffeine than green and white varieties, and the longer you steep your tea, the higher its caffeine content (5).
Research suggests that caffeine doses under 200 mg per day are unlikely to cause significant anxiety in most people. Still, some people are more sensitive to the effects of caffeine than others and may need to limit their intake further (3). If you notice your tea habit is making you feel jittery or nervous, it could be a sign you have had too much and may want to cut back to reduce symptoms.
You may also consider opting for caffeine-free herbal teas. Herbal teas are not considered true teas because they’re not derived from the Camellia sinensis plant. Instead, they’re made from a variety of caffeine-free ingredients, such as flowers, herbs, and fruit.
Overconsuming caffeine from tea may cause anxiety and restlessness. If you notice these symptoms, reduce your tea intake or try substituting with caffeine-free herbal teas.
3. Poor sleep
Because tea naturally contains caffeine, excessive intake may disrupt your sleep cycle. Melatonin is a hormone that signals your brain that it’s time to sleep. Some research suggests that caffeine may inhibit melatonin production, resulting in poor sleep quality (6). Inadequate sleep is linked to a variety of mental issues, including fatigue, impaired memory, and reduced attention span. What’s more, chronic sleep deprivation is associated with an increased risk of obesity and poor blood sugar control (6, 7).
People metabolize caffeine at different rates, and it’s difficult to predict exactly how it impacts sleep patterns in everyone. Some studies have found that even just 200 mg of caffeine consumed 6 or more hours before bedtime could negatively affect sleep quality, whereas other studies have observed no significant effect (6).
If you’re experiencing symptoms related to poor sleep quality and regularly drinking caffeinated tea, you may want to consider reducing your intake — especially if you also consume other caffeine-containing beverages or supplements.
Excess caffeine intake from tea may reduce melatonin production and disrupt sleep patterns.
Certain compounds in tea may cause nausea, especially when consumed in large quantities or on an empty stomach. Tannins in tea leaves are responsible for the bitter, dry taste of tea. The astringent nature of tannins can also irritate digestive tissue, potentially leading to uncomfortable symptoms, such as nausea or stomach ache (8).
The amount of tea required to have this effect can vary dramatically depending on the person. More sensitive individuals may experience these symptoms after drinking as few as 1–2 cups (240–480 ml) of tea, whereas others may be able to drink more than 5 cups (1.2 liters) without noticing any ill effects.
If you notice any of these symptoms after drinking tea, you may want to consider reducing the total amount you drink at any one time. You can also try adding a splash of milk or having some food with your tea. Tannins can bind to proteins and carbs in food, which can minimize digestive irritation (8).
Tannins in tea may irritate digestive tissue in sensitive individuals, resulting in symptoms like nausea or stomach ache.
The caffeine in tea may cause heartburn or aggravate preexisting acid reflux symptoms. Research suggests that caffeine can relax the sphincter that separates your esophagus from your stomach, allowing acidic stomach contents to more easily flow into the esophagus (9).
Caffeine may also contribute to an increase in total stomach acid production (10). Of course, drinking tea may not necessarily cause heartburn. People respond very differently to exposure to the same foods.
That said, if you routinely consume large quantities of tea and frequently experience heartburn, it may be worthwhile to reduce your intake and see whether your symptoms improve.
The caffeine in tea could cause heartburn or exacerbate preexisting acid reflux due to its ability to relax the lower esophageal sphincter and increase acid production in the stomach.
6. Pregnancy complications
Exposure to high levels of caffeine from beverages like tea during pregnancy may increase your risk of complications, such as miscarriage and low infant birth weight (11, 12). Data on the dangers of caffeine during pregnancy is mixed, and it’s still unclear exactly how much is safe. However, most research indicates that the risk of complications remains relatively low if you keep your daily caffeine intake under 200–300 mg (11).
That said, the American College of Obstetricians and Gynecologists recommends not exceeding the 200-mg mark (13). The total caffeine content of tea can vary but usually falls between 20–60 mg per cup (240 ml). Thus, to err on the side of caution, it’s best not to drink more than about 3 cups (710 ml) per day (4).
Some people prefer to drink caffeine-free herbal teas in place of regular tea to avoid caffeine exposure during pregnancy. However, not all herbal teas are safe to use during pregnancy. For instance, herbal teas containing black cohosh or licorice may induce labor prematurely and should be avoided (14, 15). If you’re pregnant and concerned about your caffeine or herbal tea intake, be sure to seek guidance from your healthcare provider.
Overexposure to caffeine from tea during pregnancy may contribute to complications, such as miscarriage or low infant birth weight. Herbal teas should also be used with caution, as some ingredients may induce labor.
Intermittent caffeine intake may help relieve certain types of headaches. However, when used chronically, the opposite effect can occur (15). Routine consumption of caffeine from tea may contribute to recurrent headaches. Some research suggests that as little as 100 mg of caffeine per day could contribute to daily headache recurrence, but the exact amount required to trigger a headache can vary based on an individual’s tolerance (16).
Tea tends to be lower in caffeine than other popular types of caffeinated beverages, such as soda or coffee, but some types can still provide as much as 60 mg of caffeine per cup (240 ml) (4). If you have recurrent headaches and think they may be related to your tea intake, try reducing or eliminating this beverage from your diet for a while to see if your symptoms improve.
Routinely consuming excessive amounts of caffeine from tea could contribute to chronic headaches.
Although feeling light-headed or dizzy is a less common side effect, it could be due to drinking too much caffeine from tea. This symptom is typically associated with large doses of caffeine, typically those greater than 400–500 mg, or approximately 6–12 cups (1.4–2.8 liters) worth of tea. However, it could occur with smaller doses in people who are particularly sensitive (17).
Generally, it’s not recommended to consume that much tea in one sitting. If you notice that you often feel dizzy after drinking tea, opt for lower caffeine versions or consult your healthcare provider.
Large doses of caffeine from tea can cause dizziness. This particular side effect is less common than others and usually only occurs if your intake exceeds 6–12 cups (1.4–2.8 liters).
9. Caffeine dependence
Caffeine is a habit-forming stimulant, and regular intake from tea or any other source could lead to dependence. Symptoms of caffeine withdrawal may include headache, irritability, increased heart rate, and fatigue (18).
The level of exposure required to develop dependence can vary significantly depending on the person. Still, some research suggests it could start after as few as 3 days of consecutive intake, with increased severity over time (18).
Even small amounts of regular tea intake could contribute to caffeine dependence. Withdrawal symptoms include fatigue, irritability, and headaches.
The bottom line
Tea is one of the most popular beverages in the world. It’s not only delicious but also linked to numerous health benefits, including reduced inflammation and a lower risk of chronic disease. Though moderate intake is healthy for most people, drinking too much could lead to negative side effects, such as anxiety, headaches, digestive issues, and disrupted sleep patterns.
Most people can drink 3–4 cups (710–950 ml) of tea daily without adverse effects, but some may experience side effects at lower doses. Most of the known side effects associated with drinking tea are related to its caffeine and tannin contents. Some people are more sensitive to these compounds than others. Thus, it’s important to pay attention to how your tea habit may be affecting you personally.
If you’re experiencing any side effects that you think could be related to your tea intake, try gradually cutting back until you find the level that is right for you. If you’re unsure how much tea you should be drinking, consult your healthcare provider.