ASA Confirms the Natural Variability of Isoflavones in Soybeans

The American Soybean Association (ASA) is providing this information to journalists and broadcasters as background material in advance of a study to be published in the Journal of Medicinal Foods. A recently posted abstract of a study (Lappe, et. al.) to be published in the Journal of Medicinal Foods (Vol. 1, No. 4) claims that Roundup ReadyŽ soybeans may have reduced levels of isoflavones. The authors further claim the implications are meaningful since isoflavones are potentially beneficial nutritional components in soybeans.

As a soybean organization responsible for the collection and dissemination of accurate information about soybeans and their uses, ASA believes it is important to inform you that the isoflavone content of soybeans between and within varieties does vary, so that people don't over interpret the results of this study.

ASA believes the Lappe study confirms what soybean experts already know well-that isoflavone components in soybeans are highly variable and well characterized in scientific literature. This natural variability is similar to the variability of micro-nutrients in any crop, and is greatly influenced by environmental factors. ASA has confidence in the regulatory reviews of Roundup Ready soybeans conducted by U.S. and global regulatory agencies and the underlying scientific studies that found equivalence in isoflavone content between Roundup Ready soybeans and conventional soybeans.

EQUIVALENCY

A study published in 1996 in the respected Journal of Nutrition (Padgette, et. al.) found that the isoflavone content of conventional soybeans versus Roundup Ready soybeans is comparable.

Roundup Ready soybeans are widely characterized as the most studied soybean ever grown by farmers, and were reviewed for equivalency by the U. S. Food & Drug Administration and other global agencies around the world. Over 400 individual components were analyzed in all ­ including isoflavone values ­ and the values all were well within a predictable range of variability for soybeans.

VARIABILITY

According to Dr. Stephen Barnes, professor of pharmacology and toxicology at the University of Alabama-Birmingham, "The data analyzed by authors Lappe, et al. are well within the range of variability of isoflavones exhibited in any soybean variety."

Such variability of isoflavone content is common in soybeans due to individual varietal influences and environmental factors such as weather, soil, etc. Dr. Clare Hasler, Executive Director of the Functional Foods Health Program at the University of Illinois Urbana-Champaign, and a member of the Journal of Medicinal Foods' editorial review board, also expressed concern about the Lappe paper.

"Concluding that the results of the Lappe paper are biologically relevant would be inappropriate and misleading since the scientific literature clearly suggests that isoflavone amounts in soybeans can vary as much as 300 percent or more," Dr. Hasler stated.

Global experts in soy production and nutrition technology such as Dr. Stephen Barnes and Dr. Clare Hasler also have confirmed that variability of isoflavones in soybeans, whether conventional or Roundup Ready, are well established and within the typical range one would expect to see.

ENVIRONMENTAL

Recent research being prepared for publication by the University of Illinois shows that numerous environmental factors, such as weather during the growing season, and even the slope of the field where the soybeans are grown, can lead to variability in the isoflavone content of soybeans. "Variability is due to the varietal component and the environmental component," said Dr. Don Bullock, Associate Professor of Biometry, at the University of Illinois at Urbana-Champaign. "Right now, the environmental effect is far greater than the varietal effect."

BENEFITS

According to Dr. Hasler, the hundreds of studies conducted on soy and soyfoods have pointed to significant health benefits.

"This is a truly exciting time to be in the field of functional foods," said Dr. Hasler. "We've known for a long time that soy is a good source of nutrition, and now we're seeing promising results in the use of soy to prevent or treat a variety of diseases."

Seed technologies, such as Roundup Ready, have been embraced by farmers because these products offer the potential to reduce input costs, and provide increased production flexibility in conservation tillage practices. Work also is under way to produce soybeans with output traits that will directly benefit consumers.

ASA is a national, not-for-profit, grassroots membership organization with 31,500 members, affiliate offices in 26 states, and overseas marketing offices in 13 countries. The Association develops and implements policies to increase the profitability of its members and the entire soybean industry.

For more information contact these soybean experts:

Stephen Censky, Chief Executive Officer
The American Soybean Association, (800) 688-7692,

Dr. Clare Hasler, Executive Director, Functional Foods for Health Program
The University of Illinois at Urbana-Champaign, (217) 333-6364

Dr. Stephen Barnes, Professor of Pharmacology and Toxicology
The University of Alabama at Birmingham, (205) 934-7117

Dr. Don Bullock, Associate Professor of Biometry
The University of Illinois at Urbana-Champaign, (217) 244-8221

Dr. Patricia Murphy, Food Science and Human Nutrition Department
Iowa State University, (515) 294-1970

Dr. Pamela White, Food Science and Human Nutrition Department
Iowa State University, (515) 294-9688

KEY SCIENTIFIC LITERATURE

1. Research data demonstrates that Roundup Ready soybeans and conventional soybeans are substantially equivalent in composition, safety and nutritional value.

   RESOURCES

   Composition studies show that isoflavone (also called phytoestrogen) levels are equivalent in Roundup Ready and conventional soybeans. Both Roundup Ready and conventional soybeans show a very wide range of phytoestrogen levels (5-6 fold) when grown under different environmental conditions. Padgette, S.R. et al. (1996). The composition of glyphosate-tolerant soybean seeds is equivalent to that of conventional soybeans. Journal of Nutrition 126:702-716. Data from 1992 and 1993 unsprayed Roundup Ready soybean and parental line (A5403) - 9 locations, isoflavone analysis of whole grain and toasted meal showed wide variability (5-6 fold) but no significant difference between Roundup Ready soy and the parental line. The levels of isoflavones in Roundup Ready soybeans and conventional soybeans are the same, even when Roundup is applied.
   • Taylor N.B., R.L. Fuchs, J. McDonald, A.R. Shariff and S.R. Padgette. (1999). Compositional analysis of glyphosate-tolerant soybeans treated with glyphosate. Submitted Journal of Agricultural and Food Chemistry. Data from the 1993 sprayed glyphosate-tolerant (Roundup Ready) soybean and unsprayed parental control (A5403) - 4 locations, isoflavone (6 components) analysis of whole grain. Study confirms that the application of glyphosate on Roundup Ready soybeans does not effect the levels of isoflavones or other nutritional factors. Site to site variability in isoflavone levels was high with data varying 4-7 fold, with no significant differences between Roundup Ready soybean and the parental line.

2. Isoflavone levels vary widely between soybean varieties and in soybeans grown under different environmental conditions.

   RESOURCES

   A single soybean variety contained isoflavone (phytoestrogen) levels that varied 3 fold from year to year. A 2-5 fold variation was observed between 11 US and Japanese varieties.

   • Wang, H. and P.A. Murphy. (1994). Isoflavone composition of American and Japanese soybeans in Iowa: Effects of variety, crop year, and location. J. Agric. Food Chem. 42:1674-1677. Isoflavone (12 components) levels measured in whole seed. Using a single variety over three years, total isoflavones were significantly different (varied 3-fold) from year to year. Analysis on 8 conventional US varieties and 3 Japanese varieties found wide variation (2-5 fold) in isoflavone levels that were significantly different between varieties.
   • Brazilian conventional soybean varieties showed wide variability between varieties and differed significantly between years. The variability observed was 3-8 fold. Carrao-Panizzi, M. and Kitamura, K. (1995). Isoflavone content in Brazilian soybean cultivars. Breeding Science 45:295-300. 22 conventional Brazilian soybean cultivars were analyzed for isoflavone content (2 components) over 2 years. Isoflavone content was significantly different among cultivars and between years and varied widely (3-8 fold). Total isoflavone levels varied 2-3 fold between 4 soybean varieties. This variability was attributed to climatic and environmental factors.
   • Eldridge, A. C. and Kwolek, W. F. (1983). Soybean isoflavones: Effect of environment and variety on composition. Journal of Agriculture Food Chem. 31:394-396. Total isoflavone (6 components) in whole beans was analyzed across 4 varieties and across two years. Values varied widely from variety to variety (2-3 fold) and there were also significant differences (3-5 fold) when the same variety is grown in different locations. "Significant variation among years suggests that unknown climatic and environmental factors contribute to variation in isoflavones". Additional supporting literature.
   • Fukutake, M., Takahashi, M., Ishida, K., Kawamura, H., Sugimura, T. and Wakabayashi, K. (1996). Quantification of genistein and genistin in soybeans and soybean products. Food and Chemical Toxicology 34:457-461.
   • Choi, J-S., C., Kwon,T-W. and Kim, J-S. (1996). Isoflavone contents in some varieties of soybean. Foods and Biotechnology 5:167-169.
   • Naim, M., Gestetner, B., Zilkah, S., Birk, Y. and Bondi, A. (1976). Soybean isoflavones, characterization, determination, and antifungal activity. Agric. Food Chem. 22:806-810.

3. Isoflavone variability is also observed in processed soy food products.
   • A database is available that reports the isoflavone levels in food and food products. Isoflavones vary significantly in foods and food products. USDA-Iowa State University Database on the Isoflavone Content of Foods - 1999
   • A comprehensive database and analysis of isoflavone levels in the major food sources (legumes species and processed products) of phytoestrogens in human diet. Includes data reported from references with means, ranges, and statistics. Isoflavone variation of US commodity soybean showed ranges of 3.5 fold for genistein, 3.8 fold for diadzein and 3.3 fold for total isoflavone.
   • Murphy, P.A., Barua, K. and Song, T. Soy isoflavones in foods: Database development. In: American Chemical Society Symposium Series: Functional Foods: Overview and Diseases Prevention, ed. T.Shibamoto. In press. Describes justification for, data compilation, variability, utility, interpretation and quality control of the database. Isoflavone levels vary by food product, sometimes as high as in whole bean and sometimes below limit of detection due to losses during processing.
   • Fukutake, M., Takahashi, M., Ishida, K., Kawamura, H., Sugimura, T. and Wakabayashi, K. (1996). Quantification of genistein and genistin in soybeans and soybean products. Food and Chemical Toxicology 34:457-461. Describes levels of the phytoestrogens genistein and genistin in soybean, soy nuts, soy powder, soy mil, and tofu. Levels of genistein and genistin ranged from 4.6-18.2 and 200.6-968.1 ug/g food weight in soybean, soy nuts, soy powder and from 1.9-13.9, 94.8-137.7 ug/g food weight in soy milk and tofu. Studies show that significant isoflavone losses occur during processing of soybeans.
   • Wang, C., Ma, Q., Pagadala, S., Sherrad, MS. and Krishnan, PG. (1998). Changes of isoflavones during processing of soy protein isolates. Am. Oil Chemists Society 75:337-341. Mass balance changes during processing. Describes losses of isoflavone during different steps of processing of soybeans into soy protein isolates. Study revealed that only 26% of total isoflavone remained in final processing step.
   • Wang, H-J. and Murphy, P. A. (1996). Mass balance study of isoflavones during soybean processing. Agric. Food Chem. 44:2377-2383. Mass balance changes during processing. Describes losses of isoflavone during different steps of processing of soybeans tempe, soy milk, tofu and protein isolate.
   • Wang, H-J. and Murphy, P. A. (1994). Isoflavone content in commercial soybean foods. Agric. Food Chem. 42:1666-1673. Concentration of isoflavone was analyzed in 29 commercial soy foods. High protein soy ingredients had isoflavone levels similar to that to unprocessed beans.