The study will also look into any benefits the herbal may have on PMS, or the pain and other side effects of menstruation.
Dr Chun Ng, leading the study at Queen Charlotte's and Chelsea Hospital's menopause and PMS centre, said: "It is a bit difficult at the moment to know what to give patients looking for an alternative to HRT. The majority of women that come to the clinic that aren't using HRT seem to be taking some sort of herbal remedy."
But he told NutraIngredients.com that many of the studies done on red clover extract are "not very strict", and some are not double-blind trials.
Despite this, red clover is widely used by women during menopause as it contains chemicals called isoflavones, which mimic the effects of the female sex hormone oestrogen. It is therefore seeing increasing interest as women look for alternatives to HRT following reports that it can raise the risk of stroke and breast cancer.
Leading red clover supplier Novogen said this year that its sales in Europe had risen 18 per cent during 2004, also boosted by increased marketing activity.
For the new study, the 70 subjects aged between 40-55 will also include those in the 'peri-menopausal' stage, or prior to menopause who may still be experiencing PMS.
"We have a hypothesis that the extract will work on PMS symptoms too as it is supposed to stabilize hormone levels," said Dr Ng.
The study is thought to be the first to investigate red clover's effect on PMS.
After a run-in period of two months to identify those patients with problems, the women will be randomized to receive either 40mg a day of red clover extract or a placebo for six months. At this point they will be given an option to carry on treatment for a further six months.
The researchers will look particularly at the effect on hot flushes, a symptom that affects around three quarters of all women during menopause. However Dr Ng noted that HRT will always have a more powerful effect on menopause symptoms as it is much stronger than the herbal doses commonly used.
Red clover is also used as a remedy for respiratory problems, particularly whooping cough, and for chronic skin conditions such as eczema and psoriasis.