Drinking coffee can cause stronger sugar cravings because caffeine dulls perception of sweetness, report finds

New research shows that caffeine affects the way we taste sweet flavours and could be cumulative throughout the day. But if you don’t want to cut down on your coffee consumption, there is another way...

PUBLISHED : Thursday, 31 August, 2017, 3:15pm
UPDATED : Thursday, 31 August, 2017, 3:15pm

If you are frequently tempted to buy a treat from the pastry case at your favourite coffee shop, there could be a good reason why – and it is not just your lack of willpower.

A new study on coffee has found that caffeine can affect the way we perceive sweetness and may make us crave sweets more strongly.

How much caffeine and sugar is in Hong Kong’s favourite drinks? After teen’s recent death in US, you need to know

Caffeine gives us a perceived energy jolt because it blocks receptors in our brain that monitor levels of adenosine, a chemical that can make us feel sleepy. Previous research established that adenosine also helps us taste sweet flavours.

For this new study, a team of scientists at Cornell University in New York gave participants a cup of lightly sweetened coffee, some of which were decaffeinated. They did not tell the participants whether their cup contained caffeine (the purely decaf cups contained quinine, to make sure both types of coffee had the same level of bitterness).

The ones who drank caffeine perceived their coffee to be less sweet than those who unknowingly drank decaf. When the participants were asked to taste and rate a sucrose solution more than 15 minutes later, the caffeinated participants still reported tasting lower levels of sweetness.

That finding means that the dulled palate for sweets “is a noticeable effect, and that it does stick around after you’ve finished consuming”, said Robin Dando, director of Cornell’s Sensory Evaluation Facility and an assistant professor in the university’s Department of Food Science, who was a member of the research team.

Because many people drink more than one cup of coffee a day, “this may have a cumulative effect throughout the day”, Dando added.

The research team did not measure how long the effect lasted. They also found caffeine had no apparent effect on our perception of bitter, sour, salty or umami tastes.

It has always been coffee and doughnuts, or coffee and some type of sweet … we’ve been doing this a long time, but now we understand more of the mechanism
Lauri Wright

Dando’s previous research had already found that when you chemically block a person’s ability to taste sweet flavours, it makes them crave more sugar and seek out higher-calorie treats. Based on his collective research, we now know that drinking a caffeinated cup of coffee, which has the same blocking effect, makes people want cookies or cake more than they otherwise would.

In coffee obsessed Hong Kong, independent shops are fighting for their slice of the cake

Lauri Wright is an assistant professor and director of the doctorate in clinical nutrition programme at the University of North Florida, and a spokeswoman for the Chicago-based Academy of Nutrition and Dietetics. She says: “It has always been coffee and doughnuts, or coffee and some type of sweet … we’ve been doing this a long time, this link between sugar and coffee, but now we understand more of the mechanism. This is one more reason to be moderate with our caffeine intake.”

It is also one more reason to avoid those cake pops at Starbucks. Coffee companies could certainly capitalise on these findings to promote the sales of post-coffee snacks, or to make their drinks sweeter. Perhaps, Dando theorises, they already have, without even knowing the science behind it.

“Some of these flavoured coffees, to me, they all taste very, very sweet before you put anything in there. Maybe that’s them already responding to this,” Dando said. “You might be getting 800 calories in your coffee before you’ve even sat down at your desk.”

Caffeine does, though, have health benefits too. Studies have shown that it reduces the risk of heart disease and type 2 diabetes. But the amount of sugar adults consume in their coffee, and throughout the day, could curtail some of these effects.

Currently, the Academy of Nutrition and Dietetics recommends that adults consume no more than 400mg of caffeine per day – about three cups of coffee. Fortunately for the overcaffeinated among us, the study offers an easy way to cut back. Participants reported getting an energy boost whether they were given decaffeinated coffee or caffeinated coffee. Flavour-wise, they couldn’t tell the difference. So if you want to cut back on caffeine, you should start drinking decaf.

Load of frappé: the modern minefield of coffee culture

“People have a very negative opinion of decaf, they think there’s no point in drinking it,” Dando said. “If you don’t know that it’s decaf … you might be feeling just as boosted as you might with a regular cup of coffee.”

That placebo effect works in a blind study, but it is hard to trick yourself into drinking decaf. So Wright recommends making your daily coffee with half caffeinated beans and half decaf “to gradually start weaning yourself down to moderate levels”.

Coffee for misfits: Hong Kong cafe hires and pushes troubled youth to dream big

And Dando thinks people can examine their cravings throughout the day more carefully. “I think it ultimately comes down to mindfulness, to being aware that your taste buds may not be the same throughout the day or after certain foods.”