Tea and coffee can help you wake up and stay focused, but too much caffeine can cause migraines or IBS in people who are sensitive to it.

Caffeine is a natural stimulant that stimulates nerves and mental processes by activating the central nervous system. Caffeine from coffee and/or tea has been demonstrated to improve short-term attention and alertness, as well as long-term memory, when used on a regular basis. Although most people love the “revved up” sensation of caffeine, some people are caffeine-sensitive and experience jitteriness or nausea after taking a dose. If you’re in the second group, you’ll want to cut back on caffeinated drinks or alter your intake to meet your tolerance. Caffeinated beverages should be avoided up to eight hours before bedtime for those with sleeping issues or insomnia (or omit entirely).

Caffeinated beverages can also cause migraine headaches in persons who are sensitive to them. Take warning, IBS sufferers: Caffeinated coffee or tea might trigger symptoms in some persons with IBS.

Caffeine may have some negative effects on women right before their periods. According to several studies, the effects of caffeine are amplified for women who are premenstrual. Caffeine may worsen PMS symptoms by increasing breast discomfort, anxiety, and irritability. If this is the case for you, try switching to herbal teas or decaffeinated beverages during this period.