While the caffeine in coffee can be a great pick-me-up (especially when you’re tired), could too much caffeine negatively affect your work performance? To find out more about coffee, I sat down with Cristen Harris, PhD, RD, CSSD, assistant professor in the Department of Nutrition & Exercise Science at Bastyr University in Seattle, Washington (Seattleites are actually 94% more likely to prefer espresso to bottled water than the average American).