Coffee contains caffeine, and moderate drinking can improve mental and physical strength. However, caffeine has certain toxicity, such as excessive intake, which will cause obstacles to the physiological functions of human body such as nerve activity, blood circulation and digestive system. Coffee can also affect people's heart rate, pulse and blood pressure, play a role as a stimulant, and increase the probability of myocardial infarction in people who drink coffee. Coffee can also stimulate gastric mucosa and stomach wall, leading to gastric perforation in patients with gastric ulcer. Therefore, people with heart disease, hypertension and gastric ulcer should not drink coffee.
Tea has many benefits. The World Health Organization investigated the advantages and disadvantages of beverages in many countries, and finally concluded that tea is the best beverage for human beings. According to scientific determination, tea contains 10 kinds of vitamins, including nearly 300 kinds of ingredients such as protein, fat, tea polyphenols, caffeine and lipopolysaccharide, which can regulate physiological functions and play a variety of health care and pharmacological effects.