Caffeine in human food mainly comes from coffee.

Tea trees, which originated in southern China, are now widely cultivated in India and contain caffeine, small amounts of theophylline and theobromine. Chocolate is the seed of the cocoa tree and contains theobromine and some caffeine. Theophylline and theobromine belong to xanthine and have little effect on nervous system. These alkaloids contain purine structures and are widely distributed in nature. Caffeine in human food mainly comes from coffee, followed by tea, cocoa and cola drinks. Caffeine has less nutritional effect, and most medical studies mainly analyze its pharmacological effects and side effects, as well as the response to consuming large amounts of caffeine. As a result, little is known about the potential health benefits of consuming moderate amounts of caffeine every day.

Most scientists and coffee drinkers agree that caffeine is the main component of coffee, but not the only one. The caffeine content of green Robusta beans (1.6% Mel 2.5%) is higher than that of Arabica beans (0.9% Rue 1.2%), depending on the degree of mixed coffee, and you may drink more caffeine than you think, because the degree of roasting does not change the final amount of caffeine. A moderate intake of 400-500 mg of caffeine equivalent to 4 cups of coffee a day will not be harmful to human health. Rapid intake of caffeine can cause a slight increase in arterial blood pressure, a slight increase in blood catecholamine levels, plasma renin activity and free fatty acid levels, and slight changes in urine and digestive and secretory functions. it can change brain bioelectric activity, mood and sleep type. However, long-term coffee drinking had no effect on blood pressure, serum cholesterol concentration, blood sugar level and sleep. Caffeine in coffee has nothing to do with cardiac arrest, nor with genitourinary tract cancer, pancreatic cancer, teratoma, breast fibrocystic disease. There is no evidence that caffeine intake in normal people can lead to arrhythmias, stomach or duodenal ulcers, or that caffeine is harmful to human health. In fact, drinking coffee and tea is an ancient habit, and it is recent years to study and evaluate the effects of coffee on people. Coffee contains more than a thousand chemicals, some of which are more abundant than caffeine, such as chlorogenic acid. Caffeine is the most studied ingredient in coffee, although so far studies have shown that coffee is one of the irritant substances in coffee, but this only reflects part of the truth.