The American College of Obstetricians and Gynecologists (ACOG) says that about a quarter of US women who stopped taking hormone replacement therapy after it was found to raise the risk of heart disease and some cancers have gone back on it.
New guidelines on HRT drawn up for the association by a task force of 21 national experts also concluded that herbal supplements do not relieve hot flushes.
"Treatment with wild yam extract, black cohosh, or dietary phytoestrogen supplements derived from the isoflavone red clover has no significant effects on vasomotor symptoms," the guidelines said.
"A very few limited studies have suggested that soy helps with vasomotor symptoms in the short-term (less than two years), while other studies show little difference between soy beverages or extracts and placebos," they continued.
However the number three soy isoflavone maker Solbar says it has seen no decline in demand for its products. The Israeli firm reported last year that its sales were up 30 per cent on the back of this research and marketing manager Gary Brenner says sales will be at a similar level this year.
"There has been no drop in sales or in enquiries from customers looking at this application," he told NutraIngredients.com.
But the firm's scientific adviser Tova Arditi noted that it is a false assumption to expect herbal remedies to achieve the same benefit as HRT.
"Soy isoflavones are believed to reduce frequency of hot flushes but in severe cases, they don't really help," she told us. "It is wrong to view these supplements as an alternative to HRT. There have been huge expectations from women who take them but the small effect is evident only after a period of time and many women are looking for a quick remedy."
The major Women's Health Initiative study released in 2002 found that hormone therapy could actually increase the risk of certain conditions it was previously believed to prevent, including heart attack. A further study on combination hormone therapy also found that it increased the risk of death from breast cancer.
Following the findings, sales of soy isoflavones have surged. However the US guidelines suggest that further research to prove the efficacy of herbal remedies for hot flushes may be needed to support their longevity on the marketplace.
"Approximately 65 per cent of women on hormone therapy stopped therapy after the (Women's Health Initiative)," said Dr Isaac Schiff, chair of the ACOG Task Force on Hormone Therapy. "Two years later, reports suggest that about one in four women who stopped (the therapy) went back on it because it still offers the best relief for menopausal symptoms."
He added that this trend could be seen as normal. "So we're moving back to an appropriate balance - accepting that (hormone therapy) has risks, but recognizing that it can be appropriate for conditions like hot flushes so long as women are informed about the risks and weigh their decision with their doctor."
The report calls for more research into whether hormone replacement therapy may be safer for younger women, as the average age of those studied in the Women's Health Initiative trial was 63.
It also warns that since soy and dietary isoflavones appear to affect oestrogen receptors, they may not be safe for women with oestrogen-dependent cancers such as breast cancer.
A conference in Bruges this week will focus on all of the latest research on soy and health, including its benefits for menopausal women.