Caffeine in coffee is difficult to dissolve in cold water, but easy to dissolve in hot water. Caffeine can stimulate cerebral cortex, eliminate drowsiness, increase feelings and thinking, and can be used as a cardiotonic to regulate heart function. It also has the functions of dilating renal blood vessels and diuresis. However, it is not only coffee that contains caffeine. Usually a cup of coffee contains 60-65 milligrams of caffeine. However, if you consume too much caffeine, you are prone to tinnitus and myocardial hyperfunction (the heart beats faster and the pulse frequency increases). And the pulse is uneven, so be sure to drink coffee in moderation. Coffee is recognized as a healthy drink, but drinking coffee must be reasonable and scientific, which is beneficial to health, and it should be timely and moderate. The following are some of its functions: refreshing caffeine stimulates the central nervous system, refreshing the brain and improving work efficiency; Caffeine stimulates gastrointestinal secretion of gastric acid and prevents gastroptosis. Diuretic and dehumidifying caffeine can increase urine volume and promote renal function. Linoleic acid, which has the function of promoting blood circulation and removing blood stasis, contained in coffee can hemolyze and prevent thrombosis, enhance vasoconstriction and reduce the probability of stroke. Caffeine can inhibit parasympathetic nerve and reduce the attack of asthma. Caffeine for removing odor contains tannin, which has a strong adsorption capacity for taste. If your home has just been renovated, make a pot of coffee indoors or put it indoors with cooked coffee beans, and the odor will be removed quickly. Coffee can lose weight and resist aging. Lightly roasted coffee contains more caffeine, which is beneficial to lose weight. Black coffee has antioxidant effect, which is helpful for anti-cancer and anti-aging. Drinking coffee in moderation is good for human health. Usually, the human body can consume nearly 500 to 600 milligrams of caffeine every day, which is equivalent to about 5 cups of coffee. In this range, there will be no side effects. But the metabolism of pregnant women is a little slow, so drink less. Coffee is an indispensable healthy drink for us. Yes! Drinking coffee can refresh you, and drinking a little stimulating tea is also good!