1. Refreshing: Black tea contains caffeine and tea polyphenols, which can promote blood circulation, improve mental state and relieve fatigue.

2. Protect the heart: Tea polyphenols can help reduce the content of blood lipids and cholesterol and reduce the risk of heart disease.

3. Anti-cancer and anti-oxidation: Polyphenols in black tea have anti-oxidation effect, which helps to protect the body from free radicals and reduce the possibility of cancer.

4. Improve digestion: Black tea can stimulate the peristalsis of the stomach and promote the digestion and absorption of food.

5. Prevention and treatment of dental caries: Black tea also contains a component called "catechin", which can effectively prevent the growth of oral bacteria and help prevent and treat oral diseases.

Taboo of black tea:

1. Patients with heart disease: Caffeine can stimulate myocardial function, which may aggravate the condition of patients with cardiovascular diseases.

2. Patients with digestive system diseases: Caffeine can stimulate the secretion of gastric juice, which may cause discomfort to patients with digestive system diseases such as hyperacidity and ulcer.

3. Pregnant women: Caffeine can be transmitted to the fetus through the placenta, which may have adverse effects on the development of the fetal nervous system. Therefore, pregnant women should limit their intake of caffeinated foods and drinks.