Scientific evidence says that consumption of soy from the diet or as supplements should not cause alarm despite negative reports about risks, a view that has been supported by a major US industry group.
Last week the US Center for the Evaluation of Risks to Human Reproduction (CERHR) of the National Institute of Environmental Health Services (NIEHS) and National Toxicology Program organized scientific discussions to review whether exposure to soy products may be hazardous to human development or reproduction.
The main concerns have been aimed at genistein, a naturally occurring plant oestrogen or phytoestrogen in soybeans that can mimic the effects of oestrogen in the body. Several recent studies have raised safety questions about the safety of genistein.
"There is a need to look at available evidence from reproductive and developmental animal and human toxicity studies, as well as exposure data from infants and women of reproductive age, to determine if phytoestrogens in soy infant formulas adversely affect human growth, development, or reproduction," said an official statement from the NIEHS.
After three days of discussion, the overall consensus was that, when given orally, there was no threat from the reproductive and developmental effects of soy. It should be noted that the effects of genistein in relation to heart disease or cancer risk, for example, were not explored by the panelists.
It was not a unanimous decision from the scientists however, with one panel member disagreeing with the finding and saying that greater caution was merited.
The results of the discussion have been welcomed by US trade association the National Nutritional Foods Association (NNFA), which said it was supportive of all research initiatives about the safety and efficacy of dietary supplements.
"When viewed in its entirety, the available scientific evidence, as shared during the NTP Center for the Evaluation of Risks to Human Reproduction (CERHR) panel discussion, supports the safety of soy isoflavone dietary supplements," said the organisation.
Dr Daniel Fabricant, vice president of scientific affairs for the NNFA, said that some uncertainty about the actual risks for consumers might be due to confusing the natural compound typically found in dietary supplements, genistin, with the compound in question, genistein.
Fabricant stressed that the latter, when used in supplements, is usually found only in significantly lower quantities.
Soy sales, particularly in the US, continue to grow, reaching $4 bn (£2.3bn, €3.3 bn) in 2003, according to the Soyfoods Association of North America. According to the Freedonia Group, the US soy market will grow to $8.5 bn (£4.8 bn, €7.0 bn) in 2007.
It is estimated that 10-20 per cent of infants in the US are fed soy as a supplement or replacement for maternal breast milk or cow's milk.