FRIDAY, June 13 (HealthDay News) -- Just sniffing that first hot cup of coffee in the morning may help ease some stresses you might be feeling, a South Korean trial indicates.

When rats inhaled the aroma of roasted coffee beans, a number of genes were activated, including some that produce proteins with healthful antioxidant activity, the researchers reported.

"The meaning of it is not totally clear yet," said Dr. Peter R. Martin, director of the Institute of Coffee Studies at Vanderbilt University. "What it does show is that coffee smells do change the brain to some degree, and it behooves us to understand why that is happening."

The findings, from a team led by Han-Seok Seo at Seoul National University in South Korea, were expected to be published in the June 25 issue of the Journal of Agricultural and Food Chemistry.

The experiment was done with laboratory rats, some of whom were stressed by being deprived of sleep. The researchers did detailed genetic studies that showed the activity of 11 genes was increased and the activity of two genes was decreased in the rats that smelled the coffee, compared to those who did not. In effect, the aroma of the coffee beans helped ease the stress of the sleep-deprived rodents.

The experiment provides "for the first time, clues to the potential antioxidant or stress-relaxation activities of the coffee bean aroma," the researchers wrote.

And they added, "These 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. In other words, the stress caused by sleep loss via caffeine may be alleviated through smelling the coffee aroma."

"They used the latest in technology to see how brain expression of RNA changed," Martin said. RNA is the molecule that carries out the instructions encoded in genes. "This is just the beginning of a very interesting line of investigation," he added.

The aromatic compounds responsible for coffee's odor may be antioxidants, "but they are not the same as the major antioxidants that are in the drink," said Joe A. Vinson, a chemistry professor at the University of Scranton in Pennsylvania.

Chemically, the antioxidants in liquid coffee are polyphenols, Vinson said. Those in the aroma are heterocycle compounds containing sulfur or nitrogen atoms.

"There are two ways to get things into your system, and the quickest way is to smell them," Vinson said. "Caffeine gets into the brain via the blood stream. Here, aromatic molecules get into the brain through the olfactory system. The levels in the air are parts per million, so obviously these are minor components in the air. But they are doing something."

Previous studies have shown that coffee consumption can reduce depression and suicide risk, as well as relieve stress, effects generally attributed to the caffeine in coffee, the researchers noted. But while some 900 compounds that float away from the bean have been identified, this is the first study to assay their possible effects, they added.

It's too early to recommend that people feeling stress sniff coffee to ease their way, Martin said. But, he added, "people who don't even drink coffee are fascinated by the odor of it. Ever since my little boy was two years old, he has loved the odor of coffee. I have always thought that coffee has some mystic quality, and there is some deep historical basis for it."

More information

The latest on coffee health research is available from the Coffee Science Information Centre.