Menopausal symptoms like hot flashes and vaginal dryness can be reduced with soy isoflavones in foods, supplements, and some herbal remedies.
"Hot flashes, night sweats, and vaginal dryness are very common symptoms of menopause, affecting up to 80 percent of menopausal women," said senior author Dr. Taulant Muka of Erasmus University Medical Center in Rotterdam, The Netherlands.
‘Phytoestrogens are found in soy and red clover that mimic the activity of estrogen and help reduce early postmenopausal symptoms in women.
"Many women in Western countries try herbs or other products from plants to manage these symptoms," said Muka, but these "natural" products may not necessarily be useful or safe.
"Our results simply indicate that some plant-based therapies, such as soy and red clover, can be beneficial in reducing menopausal symptoms, but some others not (e.g. black cohosh and Chinese medicinal herbs)," said Muka.
Data were collected from 62 randomized controlled trials of plant-based alternative therapies and their effects on hot flashes, night sweats, and vaginal dryness. Out of 62 reviews, 36 addressed phytoestrogens - estrogenlike molecules from plants such as soy or red clover, 16 tested black cohosh and 10 tested other medicinal herbs.
The trials totally included more than 6,600 women between the ages of 18 and 75 years. The participants were followed for between four weeks and two years.
Phytoestrogens are associated with fewer hot flashes during the day and less vaginal dryness. However, it did not influence night sweats.
Some clinical trials linked black cohosh to lessen the overall symptoms of menopause score but not specifically to fewer hot flashes or night sweats. Chinese medicinal herbs did not reduce the menopausal symptoms.
Hormonal replacement therapy is effective for menopausal symptoms in the early postmenopause, said Muka. But, it may not be an option for women at increased risk of breast cancer.
Phytoestrogens in soy can act like estrogen in the body. "This may explain the aggregate beneficial effects on menopausal symptoms we found for phytoestrogens," said Muka.
"The long-term efficacy and safety of these plant-based therapies is unclear, however, and healthy lifestyle changes form the backbone for easing the discomfort related to menopausal symptoms and keeping you healthy in the long run," he said.
A physician should be consulted before taking them as they may have some medication interactions. "There is little evidence for long-term effectiveness - or risks - of plant-based therapies, since most studies only last 12 to 16 weeks," he said.
The study is published in JAMA.