Rats, like humans, love sugar. So it comes as no surprise that during two weeks of training for a recent lab experiment, the rodents queued up twice daily for small doses of sugar water. What researchers did not anticipate was the apparent effect of the sweet stuff on their stress levels: when they placed the rats in stressful circumstances at the end of those two weeks, the animals were less agitated than expected.

Multiple blood samples taken from the rats showed lower levels of stress hormones known as glucocorticoids than those that were given a saccharin solution or just plain water before being subjected to psychological or physical duress, according to research presented yesterday at the annual meeting of the Society for Neuroscience in Washington, D.C. "We actually found that sugar snacks, not artificially sweetened snacks, are better self-medications for the two most common types of stress--psychological and physical," explains Yvonne Ulrich-Lai, a postdoctoral fellow in psychiatry at the University of Cincinnati who led the study.

Stressful events trigger the hypothalamus region of the brain, which links up with the pituitary and adrenal glands in what has been dubbed the "stress axis" to produce glucocorticoids. These stress hormones help the body defend itself under difficult conditions. But, when present in excessive quantities or for too long, they have been linked to a weakened immune system and increased abdominal fat, among other undesirable effects.

This may mean that human sugar fiends are simply warding off the sometimes overwhelming stress of modern life. "I think this research is giving us insight into something that many people may be doing already without realizing it," Ulrich-Lai says. "A lot of people when they are stressed will say that they like to eat food that tastes good." For many of us, that means sugar in its myriad forms. Yet increased sugar consumption comes with its own problems, such as weight gain. And although the rats cannily decreased their food consumption by an equivalent amount of calories when offered the sugary treat, some humans might find attaining that balance more difficult.

The ongoing research will now look at exactly how sweets decrease glucocorticoids or impact the brain and may prove that fruit or vegetables are just as effective. "I think the key is eating something you enjoy eating," Ulrich-Lai notes. But the problem may be finding something as enjoyable to eat as sugar.