Tea and coffee may wake you up and keep you focused, but don't overdo it on the caffeine — it may trigger migraines or IBS in people who are sensitive.
Additionally, caffeinated beverages can sometimes trigger migraine headaches in people who are sensitive. And IBS sufferers take note: Some people with IBS become symptomatic after ingesting caffeinated coffee or tea.
Caffeine may also have some adverse effects on women just before their menstrual cycles. Some research suggests that the effects of caffeine become magnified for women when they are premenstrual. Caffeine may exacerbate PMS symptoms and cause greater breast tenderness, nervousness, and irritability. If this is true for you, switch to herbal teas or decaffeinated beverages at this time in your cycle.