Why does caffeine affect some more than others?

How many coffees do you have a day? While many people start their mornings with a cup of coffee, some are able to swallow several espressos throughout the day, with others reduced to decaf to calm their nerves. So, just why does coffee give some people a buzz and not others? Joining guest host Clare McKenna to discuss is Registered Dietician at Orla Walsh Nutrition, Orla Walsh and Oliver from Wall & Keogh Teas.