Acupuncture may be helpful in alleviating menstrual cramps, which affect up to half of all young women, an extensive review of past studies has found.

In a review of 27 studies that involved nearly 3,000 women, researchers from the Oriental Hospital at Kyung Hee University Medical Centre in South Korea found that acupuncture may be more effective than drugs or herbal medicines.

"There is convincing evidence on the effectiveness of using acupuncture to treat pain as it stimulates the production of endorphins and serotonin in the central nervous system," they wrote in a statement.

Endorphins are compounds produced naturally by the human body during exercise and excitement and they result in a feeling of well-being. Serotonin is a brain chemical.

"Compared with pharmacological treatment or herbal medicine, acupuncture was associated with a significant reduction in pain," they added in their paper, which was published in the latest issue of the Journal of Obstetrics and Gynaecology.

However, the researchers noted flaws in the methodology of some studies and called for more clinical trials to be done.

The U.S. National Institutes of Health has cited acupuncture as a possibly effective way of dealing with menstrual cramps.

The causes for many cases of menstrual cramps are unknown, and for some women, the pain - accompanied by bloating, nausea, vomiting, diarrhea, dizziness and headache - can become more severe or may last longer as they grow older.