Conventional wisdom that says you can't do much about a poor night's sleep is wrong, and the negative effects of a sleepless night can be reversed with a brief daytime nap, a study suggests.

A quick 40 winks during the afternoon appears to restore proteins and hormones affected by the stress of sleep loss and can bring the body's immune system back up to normal, researchers found.

In a small study, 11 volunteer men between the ages of 25 and 32 were restricted to just 2 hours of sleep a night, which resulted in a doubling of their levels of norepinephrine, a stress hormone that can elevate heart rate, blood pressure and levels of blood sugar.

The also displayed reduced levels of a protein known as interleukin-6 that is involved in fighting off viruses.

On subsequent nights they were again restricted to 2 hours of sleep, but then were allowed two 30-minute naps on the following days.

After the naps, the volunteers' levels of norepinephrine and interleukin-6 were back to normal, researchers report in the Journal of Clinical Endocrinology & Metabolism.

"Our data suggests a 30-minute nap can reverse the hormonal impact of a night of poor sleep," says study author Brice Faraut of the Universite Paris Descartes-Sorbonne Paris Cite in France. "This is the first study that found napping could restore biomarkers of neuroendocrine and immune health to normal levels."

Lack of sleep can bring health problems such as obesity, diabetes, high blood pressure and depression, the U.S. Centers for Disease Control and Prevention says.

Insufficient sleep is also linked to reduced work productivity and often seen as a factor in traffic and industrial accidents, the CDC says.

Around three in 10 American adults sleeps for fewer than 6 hours a night, less than the recommended 7 to 9 hours, the National Health Interview Survey has found.

That suggests there's a need for continued research on sleep loss and ways to counteract it, Faraut says.

"Napping may offer a way to counter the damaging effects of sleep restriction by helping the immune and neuroendocrine systems to recover," he says. "The findings support the development of practical strategies for addressing chronically sleep-deprived populations, such as night and shift workers."