Does a sip of coffee give you the jitters? Blame it on your genes.

There are two kinds of people: those who can't start their day without coffee, and those who will toss and turn all night after even the weakest cup of joe. As recent research from Northwestern University in Chicago suggests, whether or not you consider caffeine your patron saint has a lot to do with your genetics.

"What we're finding is that we have built-in genetic factors that help us with self-regulating our caffeine intake," Marilyn Cornelis, a caffeine researcher at Northwestern told National Geographic. "It's interesting how strong of an impact our genetics have on that."

As Cornelis explains, the way in which caffeine affects you largely comes down to two genes that determine how the substance is metabolized in your body. The first gene, CYP1A2, produces the liver enzymes that metabolize most of the caffeine you take in. The other, AHR, determines how much of that caffeine metabolizing enzyme is actually produced.

Basically, the faster your metabolism is, the shorter your caffeine boost will be, and vice versa.

"For someone who has a genetic variant that leads to decreased caffeine metabolism, they're more likely to consume less coffee compared to someone who has a genetic variant that leads to increased caffeine metabolism."

And, if you find that drinking too much caffeine gives you anxiety, you can blame the ADORA2A gene. People with certain variations of the ADORA2A gene can experience severe anxiety from as little as 150 milligrams of caffeine—about the amount found in your typical cup of coffee.

As with any food, people's taste preferences will also determine how they feel about the ubiquitous brown liquid. Whether or not one like bitter flavors is also highly influenced by their genes.  Which bitter-receptors you do or don't have is likely to have an influence on whether or not you actually enjoy the flavor of coffee.