Coffee is a lifesaver! While it helps students pull all-nighters, it makes professionals fresh and active for work. However, we can't experience the benefits of coffee throughout the day.

In a new study by Steven Miller, a neuroscientist from the Uniformed Services University of the Health Sciences in Maryland has found that the maximum effect of caffeine can be felt if consumed between 9.30am and 11.30am.

Miller said that the best time to drink a cup of strong coffee is when levels of the hormone, cortisol, are low in the body. Cortisol controls the body clock and promotes alertness, The Telegraph reports.

When people drink coffee between 8am and 9am, their cortisol levels are usually high. They become tolerant towards caffeine and the effects are hardly helpful. The cortisol levels also peak at lunchtime and between 5.30pm and 6.30pm.

The body's levels of the hormone are usually high just after a person wakes up but start to drop about an hour later. Miller said that during these hours, people get the most benefit from caffeine.

Cortisol, which is produced in high levels in times of stress, helps convert energy into the sugar glucose to be used by the body's cells.

"If we are drinking caffeine at a time when your cortisol concentration in the blood is at its peak, you probably should not be drinking it. This is because cortisol production is strongly related to your level of alertness and cortisol peaks for your 24 hour rhythm between 8 and 9am on average," Miller said in his blog.

"One of the key principles of pharmacology is use a drug when it is needed. Otherwise, we can develop tolerance to a drug administered at the same dose. In other words, the same cup of morning coffee will become less effective and this is probably why I need a shot of espresso in mine now."

Miller said that people who drink coffee early in the morning, when their cortisol levels are naturally high, feel the urge to make their coffee stronger to get the desired effect.

However, he said that cortisol levels vary at different times of the day and from person to person as well. The best time of the day to drink coffee also differs between people to people. For example, Cortisol levels in people who get up early decreases sooner than those people who get up late.