In the days leading up to their periods, millions of women suffer mood swings, headaches and sore breasts.
But scientists think a fruit extract first discovered by Greek sages nearly 2,500 years ago can be used to beat the period blues.
Up to 40% of women suffer from pre-menstrual syndrome (PMS) so badly that they need to go to their GP and up to 2% have to take two days off a month sick.
Dieticians have given the research cautious support, but say they will be recommending women suffering from PMS try the extract.
German Researcher Rued Schellenberg from the Institute of Care and Science, near Frankfurt, found that women taking the fruit extract over three months suffered less from mood swings, anger, headaches and sore breasts than those who did not.
Extract helps
And he is calling for the extract to be considered to help women whose PMS cannot be linked to any other medical causes.
"Dry extract of agnus castus fruit is an effective and well tolerated treatment for the relief of symptoms of the pre-menstrual syndrome.
"This herbal remedy ought to be considered a therapeutic option in women."
But the study published in the British Medical Journal shows that the agnus castus extract had no impact at all in alleviating the bloated feeling associated with the pre-period days.
More than half of the 86 women given the extract had an improvement in their condition and the side effects were few and mild.
The fruits of the plant, also known as the chaste tree because it was thought to promote chastity by reducing libido, is made up of compounds similar in structure to the sex hormones.
More research
Gaynor Bussell, a dietary adviser for the National Association of Premenstrual Syndrome, said the study provided some interesting facts, but said she wants to see more research.
"I think we have got to take it seriously. Ideally I would like to see other people coming out with more research to back it up.
"But there is no harm in us saying to people to try it," she said.
Ms Bussell said that women taking hormones of any time should check with their GP before taking the extract because it does contain a natural progesterone.
She said agnus castus is already easily obtained, but said she was sure more health food shops would start to stock it because of this research.