Tea is a rich source of compounds called tannins. Tannins have the properties to bind to iron, making it unavailable for absorption in the digestive tract.
Tea contains caffeine and higher amounts of caffeine contribute to feelings of anxiety, restlessness, and stress. Black tea contains a higher amount of caffeine which means consuming it more can lead to the feeling of anxiety.
Since tea contains caffeine, it can disrupt the sleep cycle. A hormone named melatonin signals the brain that it’s time to sleep. As per some research, caffeine can inhibit melatonin production which results in poor sleep.
Certain tea compounds can cause nausea if consumed in large quantities or on an empty stomach. Tannins in tea have an astringent nature which can also irritate digestive tissue, leading to symptoms like stomach ache or nausea.
Consuming caffeine in moderate quantities helps to reduce headaches but if it is used in large quantities, the results could be the opposite. As per some studies, 100 mg of caffeine every day contributes to daily headache recurrence.