There are two types of coffee drinkers in the world.
On one hand, you have the people who take three sips of watered-down iced coffee and can't sleep for a week straight. On the other hand, you have the coffee addicts who can't function unless a constant stream of espresso is running through their veins on the reg.
This leaves us with one simple question: Why does coffee affect people so differently?
Well, thanks to science, we may have the answer. The reason why you either love or hate coffee all boils down to your genetics.
About a decade ago, Ahmed El-Sohemy, PhD, a professor of nutritional sciences at the University of Toronto, conducted a study that examined coffee's effect on the heart by looking at the gene responsible for metabolizing caffeine, called CYP1A2.
El-Sohemy found that "fast metabolizers" or people who inherit two copies of the "fast" variant of the CYP1A2 gene, had the ability to break down caffeine four times faster than people who inherit two copies of the "slow" CYP1A2 genes.
The study also revealed that drinking four or more cups of coffee each day increased the slow metabolizers' risk of heart attack by 36 percent. However, drinking up to three cups of coffee per day decreased the risk of heart attack for fast metabolizers.
The reason why slow metabolizers are more likely to experience caffeine-related cardiovascular problems is because the stimulant stays in their bodies longer. Fast metabolizers experienced health benefits from the antioxidants and polyphenols found in coffee with fewer cardiovascular repercussions.
A few years later in 2009, a study conducted by Italian researchers similarly found that slow metabolizers who drank a lot of coffee were more inclined to suffer from high blood pressure. Fast metabolizers, on the other hand, seemed to experience the opposite effect, thus decreasing the risk of hypertension as they upped their coffee consumption.
While this gene may shed some light on our coffee drinking habits, other experts like Marilyn Cornelis, PhD, of Northwestern University's Feinberg School of Medicine, argue that you can't solely look at CYP1A2, since there is a myriad of other genes involved in the process of metabolizing caffeine.
But hey, at least these findings give us some insight on why we react so differently to our morning cup of joe.