Not everyone can feel the famed buzz from caffeine, scientists claim
How we respond to coffee, whether we like the taste and even how it influences our risk of a heart attack or hypertension are all largely determined by our genes.
Our sensitivity to caffeine is largely down to one gene in particular — CYP1A2. This gene controls an enzyme, also called CYP1A2, which breaks down the drug and clears it out of our bodies – and how quickly you metabolise caffeine is dependent on the variant of this gene you have – with around half of all people having two copies of the CYP1A2 “fast” variant, making them ‘fast’ caffeine metabolisers.
According to the Washington Post, there is the 40 percent who have just one copy and are considered ‘slow’ metabolisers, with the remainder having no copies of the gene and are ‘ultraslow', says Ahmed El-Sohemy, a professor of nutritional sciences at the University of Toronto . El-Sohemy is founder of Nutrigenomix, which partners with health-care providers to conduct genetics-based nutrition testing.
The body can take as little as two hours and as much as eight hours to remove half the caffeine in your system. However, the speed of your caffeine metabolism isn’t the only factor influencing how you feel when you drink coffee or caffeinated beverages.
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Adenosine receptors in the brain – which affect a person’s need for sleep – are where caffeine works by binding to and blocking them from being activated, says Manuel Díaz-Ríos, director of the neuroscience program at Bowdoin College.
The number of these receptors in your brain is determined by both genetics and how much caffeine you regularly take. If, for example, you drink a lot of coffee, and those channels are consistently blocked, the body compensates by creating more adenosine receptors, meaning your tolerance goes up and you therefore need more caffeine for the same effect.
But some people, Díaz-Ríos says, naturally start out with higher levels of certain neuroreceptors than others. And “if you’re a person who genetically just happens to produce a lot of those receptors, then you are likely to be less sensitive to caffeine”. These people have so many of these receptors that normal or even excess amounts of coffee won’t block them all.
Genetics can also influence preference for coffee. In a 2021 study, it was found that individuals with genetic variants associated with high caffeine sensitivity were less likely to enjoy the bitter taste of dark coffee.
Sensitivity to caffeine isn’t just about whether you feel wired after drinking coffee. The genetics of caffeine sensitivity also have implications for cardiovascular health. In a 2006 study of more than 4,000 people, researchers found that for slow metabolisers, consuming more coffee per day could increase the risk of a heart attack, but fast metabolisers had no increased risk.
Slow metabolisers who drink a lot of coffee are also at higher risk of other conditions such as hypertension and kidney disease. Researchers found that when caffeine stays in the bloodstream it can cause some damage to different bodily tissues — though exactly how this happens is unclear.
A person’s caffeine metabolism also influences whether it produces a boost during exercise. Caffeine is thought to enhance performance and researchers thought that slow metabolisers would benefit more – but the opposite is true.
Researchers have measured how exercise performance in fast or slow metabolisers changes after they have caffeine. In the study, fast metabolisers were shown to cycle faster during a time trial, while slow metabolisers had slower times after consuming the drug.
Differences in fast and slow metabolizers have also been shown in handgrip strength tests. A 2012 study of 35 male cyclists analyzed the effects of caffeine on performance and showed a similar boost in fast metabolisers.
It appears that fast metabolizers get the immediate boost from caffeine, but because their body breaks it down more quickly, the caffeine doesn’t stay in their body long enough to have negative effects.
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Also, oral contraceptives can decrease CYP1A2 activity and increase your sensitivity to caffeine, while smokers process caffeine more quickly because it increases the activity of CYP1A2, and those who quit may need to cut back on coffee because they’re more sensitive to it.
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