“Caffeine is removed from your system by an enzyme within your liver,VIII which gradually degrades it over time. Based in large part on genetics,IX some people have a more efficient version of the enzyme that degrades caffeine, allowing the liver to rapidly clear it from the bloodstream. Others, however, have a slower-acting version of the enzyme. It takes far longer for their system to eliminate the same amount of caffeine. As a result, they are very sensitive to caffeine’s effects.”