The Chinese believe that good health depends on the proper flow of a vital energy called qi (chee) that moves through our bodies along invisible meridians, or pathways.

Inserting needles into particular points along these meridians, they say, can tweak this life force into proper balance. Western researchers have their own theories: One is that acupuncture triggers the release of endorphins, the body’s natural painkillers.

This idea hasn’t been proven, but a number of studies show that acupuncture does bring about real physiological changes, sometimes far from the point where needles are inserted.

In one study, for example, researchers at the University of Pennsylvania Medical Center used advanced imaging equipment to view the brains of nine patients — four pain sufferers and five healthy people — while they underwent acupuncture.

In every case, the researchers saw blood flow increase in the thalamus, a kind of relay station for pain messages in the brain, along with other changes in the brain stem and cortex.

How safe is it?

It’s very safe, as long as your acupuncturist uses either sterilized or disposable needles to prevent the spread of infection. One possible risk is bruising where the needles were inserted; the bruises are usually small and go away within a few days.

Aspirin and other pain relievers can make bruising worse, though, so be sure to let your acupuncturist know if you’re taking any.

It’s also a good idea to let your doctor know what you’re up to, so he or she can coordinate your acupuncture with the rest of your medical care. Your doctor will also want to rule out life-threatening conditions such as cancer, heart disease, and acute infections.