Scientists have discovered that drinking coffee late at night before bedtime delays a sleep hormone's increase and turns back the internal body clock by almost one hour like jet lag. Besides making it hard to fall asleep the caffeine in a latte, espresso, or cappuccino affect the sleep cycle's regular time to go to sleep at nighttime and wake up in the morning.
The study was conducted by two research teams from the United States and England, and reported in the journal Science Translational Medicine. They examined how caffeine affects individual cells.
Drinking coffee containing the caffeine content of a double espresso 3 hours before bedtime has the same effect as jet lag during a time zone change. It resets the body's internal clock. The biological clock regulates various functions and genes based on a standard day-night cycle.
Caffeine resets a person's biological clock by delaying increased levels of melatonin. That is the body's main sleep hormone, according to The Guardian.
The body's circadian rhythms are operated by a "master clock" located in the brain. It releases melatonin, which is controlled by light entering a person's eye.
Factors such as jet lag and work shifts can cause the body's clock to be out of sync. This can increase the risk of type 2 diabetes, heart disease, types of cancer, and mental decline disorders such as Alzheimer's disease.
The U.S. study took place at the University of Colorado. They discovered that drinking a double espresso 3 hours before bedtime delayed melatonin spikes by 40 minutes, according to Latinos Post. A combo of caffeine and bright light increased the delay by 105 minutes.
Then the U.K. scientists conducted lab test that discovered caffeine could turn back the body's clock. It activated a protein "switch" existing in all cells.
Co-lead author Dr. John O'Neil is from the Medical Research Council Laboratory of Molecular Biology in London. He explained that the new study showed how caffeine before bedtime affects one's body clock.
The researchers' findings could explain why caffeine beverage "night owls" go to sleep and wake up later. They could also help to treat sleep-wake disorders.
This video explains caffeine's effects: