Soy has a general healthy reputation and issues over taste, combined with a major marketing efforts over the past decade, have led to its progression from a niche health food to the mainstream.
The opinions and communications of scientists researching soy can have an impact on sales; industry executives have expressed frustration that they are not able to explain fully in their consumer marketing precisely how soy may be helpful in addressing certain health concerns or conditions.
Bernard Deryckere, president of the European Natural Soy Association (ENSA), said earlier this year that while the future looks strong, soy currently falls into a "legislative vacuum" and EU regulations need to be updated. For instance, what customers know of as soy milk cannot be labelled as such because vegetable-based products are not allowed to be called 'milk' - a scenario that leads to consumer confusion.
"Our products are still considered as food for a particular nutritional use," he said. "Thus, it is crucial for our association to raise awareness among EU officials about health benefits of soy's consumption which is part of a healthy balanced lifestyle for all categories of people."
For the new meta-analysis, published in the September issue of The American Journal of Cardiology (Volume 98, Issue 5, 571-710), researchers led by Kristi Reynolds, PhD, of Tulane University in New Orleans, US, since some studies have indicated a link between intake of soy protein, decreased total and low density lipoprotein (LDL or 'bad') cholesterol and triglycerides, and increased high density lipoprotein (HDL, or 'good') cholesterol - but not all.
They considered a total of 41 randomized controlled trials using isolated soy protein intervention as the only intervention and measuring changes in serum lipids, published in the English language between 1966 and 2005. A total of 1756 adults were involved in the trials.
After abstracting information on design, sample size, characteristics of participants, intervention, duration and treatment outcomes using a standardised protocol, Reynolds and team used a random effects model to pool and weight-up the data.
They observed significant reductions in mean serum total cholesterol, LDL cholesterol and triglycerides associated with soy protein supplementation (averages -5.26ml/dl, -4.25mg/dl and -6.26mg/dl respectively).
HDL cholesterol was seen to increase by an average of 0.77mg/dl.
Moreover, the doses of soy protein and isoflavones were seen to have some bearing on net changes in serum lipids.
Although some scepticism surrounds the conclusions drawn by meta-analyses since the quality of the studies included can vary wildly, the researchers interpret their results as an indication that supplementation with soy protein reduced serum lipids among adults with or without hypercholesterolemia.
"Replacing foods high in saturated fat, trans-saturated fat, and cholesterol with soy protein may have a beneficial effect on coronary risk factors," they concluded.
According to a report published by Euromonitor International last year, the value of Western Europe's soy milk market has more than doubled to €375m (£249.5m) between 1998 and 2004.