Research has yet to find evidence soy and garlic supplements have any health benefits at all, experts in the US agreed last week.
Garlic and soy as food may have beneficial effects on the heart, but it is not entirely clear which constituents are doing the work, experts agreed after a two-day conference on the subject.
"I have to say that in most of the areas we still have too many questions," Dr Curt Furberg of Wake Forest University in North Carolina told the conference. "I couldn't recommend too strongly any particular supplement."
The researchers said several good studies are under way that may show whether some products work, but they are years away from reporting any results.
Although soy is often proposed as a non-drug alternative to HRT, the leading botanical researchers, meeting under the auspices of the National Heart, Lung and Blood Institute, said that many of the soy-based products available vary greatly in what they contain and some may not even be in a form that can be used by the body.
"The available clinical trial results are not adequate to answer important questions about the potential cardiovascular benefits of garlic," Christopher Gardner of Stanford University in California told the meeting.
Eric Block of the State University of New York in Albany, said that stomach acid and heat may destroy some of the active ingredients in garlic. Like all plants, garlic varies greatly from crop to crop in its make-up. "We need to precisely define what we are using. We need to verify that brands contain what they are supposed to contain," Furberg said.
Some studies that suggest soy can lower blood pressure and perhaps cholesterol as well but the products are also variable and studies have not consistently compared the same products.
"Very, very high on the list is the need for standardisation of botanicals to ensure that we know what we are getting," Block said.
Dr Gregory Burke of the Wake Forest University School of Medicine noted that many soy studies are based on the observation that rates of heart disease and certain cancers such as breast cancer are much lower in China and Japan, where people eat large amounts of soy. However this may not translate to a commercial soy supplement.
"When we contrast Asia with the United States, we are comparing people who eat soy over a lifetime and not just a little shake or a little pill," Burke said.
"I think that if you are talking about dietary soy, increasing soy intake is a good thing," he added. "If you think of it as another vegetable it's a good thing. But currently, my view is that the data don't support the claim that soy and isoflavones are a viable alternative to HRT as a magic bullet."