Concerns must be addressed when sourcing isoflavones.

Increasing consumer awareness of the benefits of soy products has helped increase their sales in the United States in recent years. Sales reached $3.5 billion in 2002. Moreover, sales are expected to grow at a rate of nearly 11% annually until 2005, when they may tail off as the market reaches maturity.

A survey of manufacturers developing functional food ingredients in 2003 ranked soy proteins as second in importance after antioxidants. Although the active ingredients of soy products have not been clearly defined, some scientific evidence points to a group of 12 isoflavones as having possible health benefits.

Researchers at the University of Minnesota believe there are some critical issues which must be considered in any research program aimed at developing isoflavone-enriched foods or dietary supplements. In order to design or evaluate an isoflavone-enriched product or dietary supplement, some of the key questions to be asked relate to specific isoflavones and their possible disease-prevention properties when they are ingested at effective and safe levels. These questions may involve the choice of isoflavone source, processing constraints, quality-control procedures (which compounds should be traced) and marketing considerations.

In the Journal of Food Science (J. Food Science, 2004, 69 (3): CRH77-86), the Minnesota scientists review 80 literature references covering the bioavailability of isoflavones, their thermal stability, the sources of isoflavones, dosage considerations and methods of analysis.

The investigators present a critical review of the safety and efficacy of soy isoflavones used either to enrich foods or as dietary supplements. The researchers conclude that the scientific literature available is not sufficient to give a clear picture of either the health benefits or health risks of soy isoflavones.

Thermal processing appears to have no impact on isoflavones, but a lack of data on activity and bioavailablity means that dosages cannot be properly determined. In terms of bioavailability, aglucons were not found to be superior to conjugated isoflavones, so there may be questions over the recent trend to develop aglucon-enriched products.

Further information. Ted Labuza, University of Minnesota, Department of Food Science and Nutrition, 225 FScN, 1334 Eckles Ave., St. Paul, MN 55108; phone: [phone]; fax: [phone]; email: [e-mail].