Coffee can help you stay more alert if you spread its consumption throughout the day. This means that most people can drink two to four 8-ounce cups of coffee a day without experiencing harmful effects.
Drinking coffee may also help maintain mental health longer. A study investigating the relationship between coffee consumption and mental decline revealed that consuming no more than three cups of coffee daily helps reduce cognitive decline, according to an article published in "European Journal of Clinical Nutrition" in February 2007