Food and diet

Wake up and smell the coffee

“Just the smell of coffee could be enough to wake us up in the morning”, reported The Daily Telegraph today. The newspaper explained that in a study on thirty sleep-deprived rats, brain activity - measured by levels of “messenger molecules” - was boosted in those which had smelt roasted coffee beans compared to those that had not. According to the report, the researchers suggest that this study could lead to factory owners pumping the smell of coffee into their building to revive flagging workers.

The Daily Telegraph’s report is based on a small experimental animal study. The study forms the basis for further research, but the implications for humans are unclear at this stage. The researchers offered a possible explanation as to why people feel bad when they have not had enough sleep, but they also acknowledge that further work needs to be done in testing whether the same genes are suppressed in sleep-deprived humans, testing whether this suppression leads to feeling tired, and identifying the active ingredient in coffee.

Where did the story come from?

Dr Han-Seok Seo from Seoul National University in South Korea and colleagues from research centres in Germany and Japan carried out the research. The study was partly supported by the Winter Institute Program of the Korea Science and Engineering Foundation and the Japan-Korea Industrial Technology Foundation. The study was published in the peer-reviewed medical journal Journal of Agricultural and Food Chemistry .

What kind of scientific study was this?

This experimental animal study investigated the effect of roasted coffee bean aroma on the function of the rat brain. The researchers did this by studying proteins from rat brains and looking at how they were affected in the cell by the activity of messenger RNA (mRNA) molecules. These molecules are a reflection of gene expression within the cell, and transmit genetic information from DNA to the protein synthesis machinery in cells, where they are involved in the production of proteins.

The researchers also evaluated the impact of roasted coffee bean aroma on stress induced by sleep deprivation in the rats. Rats were chosen as subjects because they are genetically similar to each other and because there is already a large body of research on the effects of stress, brain function and gene expression in rats.

The researchers sourced a Columbian variety of green coffee beans from the local coffee roastery in Seoul. The beans had been roasted in a drum roaster to a medium-dark degree. They then picked 30 ten-week-old rats and randomly divided them into four groups: a ‘control group’, a ‘stress group’, a ‘coffee group’ and a ‘coffee plus stress group’. The control group (seven rats) and the stress group (eight rats) were not exposed to coffee smells, and the stress group were deprived of sleep for 24 hours to make them stressed. The two other groups were both exposed to the coffee aroma with one group (the coffee plus stress group) also sleep-deprived.

The researchers then dissected the brains of the animals and examined them using several different techniques, which included extraction of the mRNA, extraction and quantification of the proteins, and also specialised mass spectrometry to further identify the changes in specific proteins involved. They focused on the effects on 17 genes known to be associated with smell and stress.

What were the results of the study?

The researchers compared gene expression by measuring the amount of mRNA found in the different groups of rat brains. When they compared the ‘stressed with coffee group' to the ‘stressed without coffee group', they found that the levels of mRNA for 11 genes important to brain function were increased in those exposed to coffee smells compared to those without. These increased levels approached those seen in the unstressed rats. For two genes, the levels were pushed further above “normal”.

What interpretations did the researchers draw from these results?

The researchers say that their results “indirectly explain why so many people use coffee for staying up all night, although the volatile compounds of coffee beans are not fully consistent with those of the coffee extracts”. This, they say, could mean that the stress caused by taking caffeine (i.e. sleep deprivation) could be reduced by smelling coffee.

What does the NHS Knowledge Service make of this study?

The researchers have reported an animal study, which will form the basis for further research. The study is reliable in that it evaluated the effects of coffee aroma on the levels of mRNA in rat brains. However, the implications for humans are by no means clear. 

Further research in this area will need to address such questions as whether the same genes are suppressed in sleep-deprived humans, and if people would feel tired if these genes were suppressed. It is also not yet clear what the active ingredient in coffee is, and if it is better to drink or smell it.

Sir Muir Gray adds...

If anyone offers me a smell of a cup of coffee rather than the real thing they had better watch out!

NHS Attribution