Through a series of tests, researchers at the University of Wales in the United Kingdom examined the effects of breakfast and coffee on mental alertness in the late morning and after lunch. The patients were tested at 7:45 am and then given breakfast and coffee. An additional cup of coffee was given at 11:15 am. The patients were then tested again both before and after lunch.

The study found that the coffee increased the patients' mental alertness and ability to perform a task over a prolonged period of time. In addition, drinking coffee also helped improved their mood and overall feeling of well-being.

A study performed at The Netherlands' University of Amsterdam looked at how moderate amounts of coffee affected brain function and overall mental awareness. The results proved that coffee did improve brain function, without adversely affecting unrelated parts of the brain and the patients' health.

People who need to keep awake through longer periods, such as students studying for exams and employees working overtime, often drink coffee to stay mentally active. To scientifically test coffee's effectiveness during such times, the Division of Sleep Medicine at the Brigham and Women's Hospital together with the Harvard Medical School in Massachusetts conducted a study where the patient was kept awake for long periods of time. They were kept awake for over 42 hours at a time, and then allowed to sleep as necessary, over 29 days. The patients studied were healthy men between 18 and 30 years of age with no sleeping issues.

The researchers found that coffee did cause a marked difference in the mental alertness of the patients during their waking periods. In addition, the patients were able to stay completely awake for longer periods of time. The study suggested that taking a decent amount of coffee over a prolonged period of time was indeed helpful in increasing mental alertness when one needs to be awake for a considerable amount of time.

Aside from keeping one mentally alert, other studies have shown that your memory also benefits from drinking your coffee.