A coffee could reset your body clock and cheat jet lag

Drinking a double espresso at night may not only keep you awake longer, but could also push you into a whole new time zone, new research suggests. “It’s in your liver, for example, as well as in your brain”.

Scientists have had hints that caffeine could alter cellular timekeeping, from studies in bread mold, green algae and sea snails. This then can make you want to go to bed later, and lead to things such as daytime sluggishness.

Caffeine resets the clock by delaying a rise in the level of melatonin, the body’s chief sleep hormone, which fluctuates in levels to help determine the natural time to go to sleep and wake up.

But the study also says that daylight is an even greater disruptor of circadian rhythm. It was about half the effect the scientists noticed when they instead exposed the volunteers to bright light.

Though the study links caffeine to changes in the circadian clock, Roehrs said the cellular effects in the lab may not explain the sleep delays seen in the human subjects.

Dr John O’Neill, the joint lead researcher at the council’s Laboratory of Molecular Biology, said: “These findings could have important implications for people with circadian sleep disorders, where their normal 24-hour body clock doesn’t work properly”. However, its effect on our biological clock and internal rhythm hasn’t been well understood. “Based on this, I say 5 to 6 PM would be the latest most people would want to have a coffee or other caffeinated beverage”, he says. Because of this, Burke says people need to be much more considerate of the times they drink caffeine.

The study could prove helpful to people with sleep disorders and people who naturally woke up too early.

“Caffeine is one of the most widely consumed drugs that’s legal, but is also has these psychoactive impacts”. NPR’s Nell Greenfieldboyce reports that scientists have just discovered something about what it can do to your body.

At issue: The body’s circadian clock, which sets biological rhythms such as sleep/wake cycles.

GREENFIELDBOYCE: Kenneth Wright is a sleep and circadian physiologist at the University of Colorado, Boulder. Every cell in the human body has a clock, Wright said.

GREENFIELDBOYCE: And irregularities in the circadian clock have been linked to everything from obesity to cancer.

WRIGHT: To our surprise, no one had really tested this question.

The researchers found that the participants who took the caffeine pill in low light conditions experienced a roughly 40-minute delay in their circadian patterns compared to those who took the placebo in low light conditions.

The findings were reported last night (WED) in medical journal Science Translational Medicine. The Medical Research Council and the Wellcome Trust also helped to fund the study. The experiment showed that intake of coffee in the evening slowed the body clock by 40 minutes. He adds that a lifestyle with irregular sleeping habits and poor quality sleep is bad for the organism, because the circadian body will be out of sync with the one of the natural world.

The study was double blind placebo controlled, so neither researchers nor subjects knew if they were consuming a placebo or caffeine.