Several years ago, 1970's, there was a study that received wide publicity about how double white feverfew was effective in the elimination and/or cessation of migraine headaches. The participants actually consumed 2 - 3 leaves daily to aid or prevent the occurences.
The active ingredient in feverfew is parthenolide. When people in the U.S. tried to duplicate the results with the exact same species of plants the success was not there. What was later determined was the active ingredient, parthenolide, was not abundant in the leaves of a warmer climate versus the cooler climate of Canada. In order to duplicate the results the flower of feverfew was what had to be consumed. Feverfew does appear to be a potential natural herb for use in the treatment of migraines as well as certain forms of arthritis. It is somewhat disputable as to the efficacy of certain pills as many times there is a lack of the active ingredient you find in the plant itself.