Walk down a busy office street and you’re likely to see many smokers with a cup of joe. I used to think coffee tasted better after a cigarette. Turns out scientists have a different answer.
A study published last month has found that an inherited genetic variant that causes people to smoke more might also cause them to crave more caffeine. You can have zero, one, or two copies of the variant in a gene called CHRNA5. The study found that each copy of the gene led to an increase in smoking of one more cigarette per day and 0.15 cups of coffee per day.
“You could extrapolate from that and say that if you smoked 10 cigarettes per day more than the next person, you would be drinking the equivalent of about one and a half extra cups of coffee per day,” Marcus Munafò, the lead researcher, told the New Scientist. He doesn’t know yet what the actual purpose of gene variant is, but the side effect shows up clearly in the data.
To come to this conclusion, scientists at the University of Bristol looked at the smoking and coffee drinking habits of 250,000 people in the UK, Denmark, and Norway. Munafò looked at tea consumption and saw a similar spike in the UK, where tea is the drink of choice.
That’s not all. A 2004 study found that the byproducts of smoking enhance the activity of liver enzymes (called cytochrome P450 isoenzyme 1A2 and UDP-glucuronosyltransferases). These enzymes are what cause metabolism, a form of chemical chewing within the body, which means smokers lose the effects of caffeine faster. So it’s likely that smokers need to consume more coffee to get the same hit that non-smokers get. (The same enzymes are also known to enhance the metabolism of anti-psychotic drugs, such as olanzapine and clozapine.)
According to a 2014 study, smoking also blunts taste buds, especially for the bitters in caffeinated drinks. Some smokers might claim that the blunting is taste-enhancing, but coffee connoisseurs likely turn up their noses at such an excuse.