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For smokers, coffee and a cigarette just seem to go together. Before most restaurants banned smoking, it was common to see folks enjoying coffee and an after-dinner smoke, and it was a common joke among wait staff that smokers asked for more refills. Now, scientists believe they’ve found a causal link between smoking and drinking more coffee – or, in plain English, some scientists now think that smoking makes people crave more caffeine.
A group of scientists led by Marcus Munafò at the University of Bristol, UK, published a study on the relationship between smoking and coffee consumption. They found that people who smoke cigarettes also drink more coffee and that the more they smoke, the more coffee they drink.
The researchers studied the drinking and smoking habits of 250,000 people culled from biobanks in Denmark, the UK and Norway. Those biobanks contain dietary, lifestyle and medical information about thousands of participants. For this study, the scientists specifically looked for people who have a genetic variant in the CHRNA5 nicotinic receptor, a gene variant linked to smoking.
In an interview with New Scientist, Munafò explained that people can have zero, one, or two copies of that particular gene variant. Scientists already know that people with more copies of CHRNA5 smoke more cigarettes per day. Rather than asking people how many cigarettes they smoked daily, Munafò’s team used the CHRNA5 gene as a proxy – the more copies of the gene, the more cigarettes they assumed the person smoked. They used information about coffee and tea consumption that people had recorded in the original studies to determine how much coffee or tea each participant consumed.
Do Smokers Drink More Coffee?
In a word, yes. Munafò’s team found that people who carry that gene variant do drink more coffee than people without it – but only if they also smoke. Nonsmokers with the gene variant showed no difference in the amount of coffee they drank, regardless of the number of copies of the CHRNA5. And since CHRNA5 does not directly interact with caffeine, the researchers believe that the increase in caffeine consumption is possibly caused by the increase in nicotine consumption.
What Does It Mean?
Munafò does concede that it’s not the only possibility. It could just be that people pair coffee and smoking out of habit until they link them psychologically. He thinks, though, that nicotine may change the way that the body metabolizes caffeine – that smokers metabolize caffeine more quickly, so they need to consume more coffee to get the same effect from caffeine that non-smokers get. If he’s right, the information could be used in the future to help people quit smoking. Munafò suggests, for example, that coffee drinkers may have more trouble quitting if they continue to drink the same amount of coffee. Because their bodies are no longer metabolizing caffeine as quickly, they’ll notice an increase in caffeine’s effects but think it’s nicotine withdrawal. Understanding the link between caffeine and nicotine consumption could help develop new strategies to get through nicotine withdrawal.