The effectiveness of caffeine depends on the time it takes to drink coffee.

When a person feels sleepy, hungry, happy or sad, the body's circadian rhythm is responsible for calling the shots. The body clock is responsible for controlling the sleep-awakening cycle, hormone release, body temperature and other functions. According to the website, cortisol is a stress hormone that increases sugar in the blood, usually secreted by the body shortly after getting up in the morning. Healthy people have a 50% increase in cortisol levels during the first 20 to 30 minutes after waking up in the morning. With the peak of cortisol in the blood, it can increase the body's alertness and help the body regulate its circadian rhythm, a caffeine-free natural boost.

Stephen, a neurologist from the University of Health Science Unified Service in Bethesda, Maryland, USA. Miller, who wrote on NeuroscienceDC, a Washington-based science news blog, said people should not drink caffeinated drinks early in the morning when cortisol levels are at their peak.

"Drug tolerance is an important issue, especially when we overuse caffeine," he wrote. "therefore, when the concentration of cortisol in the human blood reaches its peak, caffeinated drinks should not be drunk."

People who drink coffee at high cortisol levels usually drink coffee at 8 and 9, which makes them more likely to tolerate caffeine. This increase in tolerance means that caffeine is less effective in the body. Miller explains this phenomenon with one of the main principles of pharmacology: the use of a drug when needed.

"in other words, the same morning coffee will become less effective, which is probably why I need an espresso." He wrote that the Daily Telegraph reported.

To maximize the benefits of caffeinated drinks, you should drink coffee between 9:30 and 11:30, when cortisol levels drop before the next wave of peak. Blood cortisol levels peak between 8am and 9am, between 12:00 and 1pm, and between 5:30 and 6:30. Miller admits that cortisol levels vary from person to person at different times of the day, which means the best time to drink coffee varies from person to person. People who get up early usually have a faster drop in cortisol than those who get up late.

Coffee not only increases alertness, but also benefits your health. A study published in the journal Hepatology found that drinking a cup of coffee or tea in the morning can protect drinkers from liver failure. The researchers used cell culture and mouse experiments to study the effect of caffeine on nonalcoholic fatty liver disease (NAFLD). Eating caffeine stimulates the metabolism of oils stored in hepatocytes and reduces the content of liver lipids in mice on a high-fat diet. If people drink several cups of coffee or tea every day, these findings can also be applied to humans to prevent the progression of fatty liver, especially those on a high-fat diet.

According to a 2013 online survey by the National Coffee Association, 83% of adults in the United States drink an average of three cups of coffee a day. The United States is still the world's largest consumer of caffeinated drinks.