one way valve found that people like to enjoy a cup of coffee when tired, because caffeine can go directly into brain through blood, in fact, there are not many of such these substances. In the brain, caffeine can inhibit adenosine—there is hormones which have sedation, hypnotic effect, and play an effect of "keep us one’s spirits”.
Two years ago, the IARC has relieved the warning of “coffee carcinogenic" which started in the 1990s, and explained that why they come up with this conclusion because they don't pay enough attention to the role that smokers play in it. Due to smokers usually drink too much coffee, and smoking increases the risk of cancer. In other words, smoking causes cancer, not coffee.
Last year, the IARC published the most authoritative research report on coffee and health, and trace 500,000 coffee drinkers in 10 European countries to do a long term test, and analysis all data to reach the conclusion. It shows that the coffee drinkers have a much lower risk of dying from various diseases, including cardiovascular and gastrointestinal problems.
So, is it better to drink more coffee? The medical workers remind people that coffee can be addictive, you will turn out headaches and nervous symptoms if you want to quit after addiction. In other words, if you want to enjoy coffee normally and healthily, its "kingly way" is to master the amount of coffee.