There is no strong evidence either way for several herbal remedies commonly taken to relieve troublesome menopausal symptoms, concludes the January issue of the Drug and Therapeutics Bulletin ( DTB ).
And for some, there is hardly any evidence at all.
Between 30% and 70% of women in industrialised countries will experience vasomotor symptoms around the menopause, such as hot flushes and night sweats, prompted by the sharp fall in oestrogen levels.
On average, such symptoms last for around four years, but in around one in 10 women, they can last more than 12 years.
Herbal remedies commonly used to relieve menopausal symptoms include black cohosh, red clover, Dong quai, evening primrose oil, and ginseng. Others include wild yam extract, chaste tree, hops, sage leaf, and kava kava.
But little good quality evidence on the effectiveness of herbal medicines, or how they might react with prescription medicines is available, says DTB .
And, in general, safety has been under researched, which is a major concern given that herbal remedies are often assumed to be "safe" just on the grounds that they are "natural," says DTB .
Published studies are often poorly designed, include too few participants, or don't last long enough to be of real value.
Furthermore, the chemical make-up of various preparations of the same herb may differ, which can make it difficult to compare trial results.
The drugs regulator, the Medicines and Healthcare products Regulatory Agency (MHRA), has given a Traditional Herbal Registration to Menoherb, which contains black cohosh, under a scheme designed to boost the safety of herbal products on sale.
But clinical trial data on black cohosh are "equivocal," says DTB , with some studies suggesting that the remedy works well, while others suggest that it does not relieve symptoms effectively.
Liver toxicity is also a potential side effect of black cohosh.
There is "no convincing evidence" that red clover extract is effective, says DTB , and little evidence one way or another for dong quai, evening primrose oil, wild yam, chaste tree, hops, or sage.
This review appears in the new look DTB, which has been given its first major design make-over since it was first published in 1962.
Pagination has also increased from eight to 12, in a "deliberate attempt to address healthcare professionals' needs for clear, succinct information and practical advice on medicines, other treatments and the overall management of disease," says an editorial, another new feature of the redesign.
Other additions include the use of colour and a new layout, which will allow for illustrations, to make DTB both even more informative and more enjoyable to read.
Commenting on the move, DTB editor Dr Ike Iheanacho, said:
"For over 45 years, DTB has strived to produce rigorously researched information and advice for healthcare professionals, to help ensure patients get the best possible care. The newly redesigned version of the publication aims to continue and build on this tradition."