There is little evidence that herbal remedies relieve symptoms of menopause, and some may have potentially dangerous interactions, according to a new review.

In Wednesday’s issue of the Drug and Therapeutics Bulletin, published by the British Medical Association, researchers reviewed clinical trials on the safety and effectiveness of herbal medicines.

Herbal treatments may be taken to ease hot flashes, night sweats and loss of libido that may occur as estrogen levels fall around menopause. It's estimated that 30 to 70 per cent of women in industrialized countries have menopause-related symptoms.

Herbal remedies taken for menopausal symptoms include:

  • Black cohosh (Actaea racemosa).
  • Red clover (Trifolium pratense).
  • Dong quai or dong gui (Angelica sinensis).
  • Evening primrose oil (Oenothera biennis).
  • Ginseng (Panax ginseng).

Some people may think that the natural products, which are sold in stores and online, are risk-free, said journal editor and review author Ike Iheanacho.

"In reality, however, herbal medicines have pharmacological actions, and so can cause unwanted side-effects and have potentially dangerous interactions with other medicines, both herbal and conventional," he wrote.

Herbal trials often not scientifically rigorous

Iheanacho's review of published studies and scientific commentary concluded there is mixed evidence on the benefits of black cohosh for easing menopausal symptoms. Liver toxicity is a potential side-effect of black cohosh.

There is "no convincing evidence" that red clover extract is effective, the review concluded.

There was also little evidence that less commonly taken remedies such as dong quai, evening primrose oil, wild yam, chaste tree, hops or sage made much difference.

Much of the published research was not rigorous enough to assess safety and effectiveness. Many studies included too few participants, the trials were too short to provide definitive answers, or different preparations of the same herb made it difficult to compare trial results, the review concluded.

On average, Iheanacho said, symptoms last about four years, but for one in 10 women, they can persist for more than 12 years.

Sales of hormone replacement therapy have fallen since 2002, when a major study found increased rates of breast cancer, heart attacks, strokes and blood clots among women taking the hormones.