What are the dangers of strong tea to human health?

Neurologist Valentina Isaeva in an interview with SOLENKA.INFO told about the dangers to human health of strong tea, which is a familiar and favorite drink for residents of many countries around the world. 
According to the neurologist, strong tea is a too concentrated or long brewed drink. The specialist gave several tips for making tea:
- The amount of tea brew should not exceed 1 tsp per 200-300 ml of water;
- brewing time for black tea should be no more than 5 minutes, for green tea - no more than 3 minutes, for white tea - 1 minute, and for puerh - from 30 seconds to 3 minutes.
In addition, the expert recommends drinking no more than five cups of freshly brewed and non-strength tea a day. People who have trouble sleeping should refrain from drinking tea after 6 p.m.
Isaeva noted that strong tea and its excessive use may lead to the following unpleasant consequences:
1.     Iron deficiency. As a result, the condition of the hair and skin deteriorates, there is constant fatigue and iron deficiency anemia occurs.
2.     Disruption of the digestive process. Caffeine in tea can provoke heartburn, acid reflux, exacerbation of gastritis and ulcers, and intestinal disorders.
3. negative effects on the nervous system: increased anxiety, nervous exhaustion, changes in the psychoemotional state and dependence, similar to alcohol or drug addiction.
4.     Disturbance of the quality of sleep, insomnia.
5.     A detrimental effect on the cardiovascular system.
6.     Negative effects on the liver. The fact is that tea leaves grown in poor environmental conditions may contain heavy metals. In addition, tea with flowering plants added sometimes contains pyrrolizidine alkaloids - toxins that negatively affect the liver in large quantities.
7.     Destruction of bones and teeth. Strong tea or excessive consumption of this beverage greatly increases the amount of fluoride in bone tissue, which can result in brittle bones and tooth loss.