Women may find some relief from menstrual cramps by taking
vitamin E a few days a month, according to a new study of 278
teenage girls in Iran. Half the teenagers were given 200 mg of
vitamin E twice a day, starting two days before they expected
their periods and continuing through the third day of
menstruation. The other half received a placebo pill. Both groups
were allowed to take ibuprofen as needed.

After four months, the girls who took vitamin E had cramps for
less than two hours, on average, during their periods. That
compared with 17 hours for those who did not take the vitamin. In
addition, only 4% reported using ibuprofen, compared with 89% of
girls in the placebo group.

Common menstrual cramps (dysmenorrhea) are thought to result from
the release of hormone-like substances called prostaglandins.
Prostaglandins cause the uterus to contract in order to expel the
uterine lining, resulting in menstrual blood flow. Vitamin E can
inhibit the formation of prostaglandins — and, potentially,
menstrual cramps.

Source: British Journal of Obstetrics and Gynaecology, April 2005