Just the smell of freshly brewed coffee can help relieve stress, say researchers who studied the effects of coffee aroma on sleep-deprived rats.
Roasted coffee bean aroma created higher activity in a number of genes in the rat brain, including some that produce proteins with antioxidant activities, according to the study carried out by researchers at Seoul National University in South Korea and published recently in the Journal of Agricultural and Food Chemistry.
This provides "for the first time clues to the potential antioxidant or stress relaxation activities of the coffee bean aroma," wrote the scientists.
Antioxidants, such as vitamins A, C and E and carotenoids like beta-carotene, are believed to exert a protective effect on cells. They scavenge toxic molecules called free-radicals, which cause oxidative stress and can lead to DNA cell damage.
Coffee is the most widely consumed beverage worldwide, with between 70 and 80 per cent of the human population drinking it, said the study.
As a result, the beverage has been widely studied. Health benefits identified by scientists include findings that drinking three or more cups of coffee per day may reduce the risk of ovarian cancer by over 20 per cent, and that unroasted green coffee bean extract taken as a drink or supplement can help people reduce weight.
The aim of the study was to demonstrate influences of roasted coffee bean aroma on rat brain functions and to evaluate its impact on stress induced by sleep deprivation.
Green coffee beans were used and their aroma exposed to rats that had been sleep deprived for 24 hours (stress with coffee group), as well as to rats that were not stressed (coffee group), and the results were compared to a control group and stressed rats that were not exposed to the aroma (stress group).
Analysis was carried out on some of the genes associated with aroma or stress.
The researchers found that, compared to the control animals, the expressions of 17 selected genes were different in the coffee group. And 13 genes were different between the stress group and the stress with coffee group, with 11 being up-regulated and two being down-regulated.
The change in protein profiles was also analysed using two-dimensional gel electophoresis, and nine proteins were identified.
The genes belonged to five functional categories: antioxidant; protein fate; cell rescue, defence, and virulence; cellular communication/signal transduction mechanism; and energy metabolism.
The authors wrote: "The results of this study allowed us to improve our knowledge involved in relationships among coffee bean aroma, brain function, and stress via sleep deprivation."
They said that further studies using complementary techniques, such as DNA microarray for gene expression, are needed for increased understanding and verification of these results.
Additionally, they said: "When we stay up all night, is it better for us to smell coffee bean aroma than to drink coffee, or would any other food-related odour produce similar effects? Further studies are needed for not only obtaining the correct answer for this question but also identifying the potential volatile compounds for this beneficial effect."
Journal of Agricultural and Food Chemistry
Volume 56, pages 4665-4672, doi: 10.1021/jf8001137
"Effects of Coffee Bean Aroma on the Rat Brain Stressed by Sleep Deprivation: A Selected Transcript and 2D Gel-Based Proteome Analysis"
Authors: Han-Seok Seo, Misato Hirano, Junko Shibato, Randeep Rakwal, In Kyeong Hwang, and Yoshinori Masuo