1. Children's tea contains tannic acid, which can precipitate iron in food and oxidize bivalent iron into trivalent iron, making iron unusable and causing iron deficiency in the body. If children develop the habit of drinking tea for a long time, it will easily lead to iron deficiency and anemia, which will affect their intellectual development and make their intelligence (including understanding, memory and responsiveness) decline. Therefore, children should not drink tea, let alone drink tea for a long time.
2. Malnourished people drinking tea will affect their body's absorption of protein. After tannic acid in tea combines with protein to form tannic acid protein, it cannot be digested and absorbed by gastrointestinal tract. Malnourished people will have worse nutrition if they drink tea.
3. Tannic acid in tea of anemia patients and pregnant and lactating women will affect the absorption and utilization of iron and aggravate the degree of anemia. Pregnant women and lactating women should not drink tea, otherwise it will easily cause diseases such as anemia in adults or fetuses and infants.
4. The tea of patients with cerebral arteriosclerosis contains caffeine, theobromine and other substances, which has obvious exciting effect on the central nervous system. Patients with cerebral arteriosclerosis will cause cerebral vasoconstriction after drinking tea, resulting in insufficient blood supply to the brain. Therefore, such patients should not drink tea.
Caffeine in tea has an exciting effect on patients with hypertension and heart disease, which will increase blood pressure and accelerate the heartbeat, so patients with hypertension and heart disease should not drink strong tea.
6. Caffeine in the tea of patients with neurasthenia, insomnia, hyperthyroidism, tuberculosis and other chronic diseases is exciting, which will increase the basal metabolic rate, thus making it impossible for these patients who need to be quiet to get a good rest and sleep.
7. Tannic acid in constipation tea has astringent effect, which can lead to constipation aggravation.