Acatris, the Dutch health ingredients company, has called for greater harmonisation of the methods used to test soy isoflavones to help consumers avoid "the proverbial problem of comparing apples to oranges rather than apples to apples".
Acatris assessed the testing procedures of universities and laboratories in Europe, the United States, Canada, Japan and Australia and discovered that there was considerable variation among the techniques used to establish isoflavone levels.
The analysis was carried out by TNO Nutrition and Food Research on the procedures employed by 22 laboratories from around the world. The laboratories were asked to analyse the level of isoflavones in duplicate samples of three soy preparations using their current method of analysis, as well as to submit their method of analysis for further statistical comparisons.
Twenty laboratories used an HPLC method, one laboratory used an enzyme-linked immunosorbent assay (ELISA), and the last used capillary electrophoresis. Although the results were positive for the laboratories' ability to duplicate the same results twice, the variation between the laboratories' results were statistically unacceptable, Acatris claimed.
The reasons for this included variations in the method of analysis such as differences in the extraction conditions, differences in the molar extinction coefficients used to calculate isoflavone values and an unknown purity of the standards used to compare the soy isoflavones.
The company pointed out that the Association of Official Analytical Communities (AOAC) has already developed a soy isoflavone testing method for food, which it released last December, and called for this or an equivalent universal method to be adopted as soon as possible to avoid confusion over isoflavone content - a factor which is becoming increasingly important as soy food sales continue to benefit from the good press about their health benefits.
Acatris pointed out that the AOAC method did not address measuring isoflavone levels in biological systems, and that this meant it was still unclear whether soy researchers would adopt it or continue to use their own various methods. However, it added that it would continue to search for opportunities to champion a uniform method of soy isoflavone analysis.