ASA Response to: "Alterations in Clinically Important Phytoestrogens in Genetically Modified,
June 23, 1999
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
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
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.
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."
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
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
- Research data demonstrates that Roundup Ready soybeans and conventional
soybeans are substantially equivalent in composition, safety and
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
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
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
- Isoflavone levels vary widely between soybean varieties and in soybeans
grown under different environmental conditions.
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
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
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.
- 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 -
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.
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
- 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
Dr. Clare Hasler* Executive Director
Functional Foods for Health Program
University of Illinois at Urbana-Chaqmpaign
103 Agricultural Bioprocess Lab. (M/C 640)
1302 West Pennsylvania Ave.
Urbana, IL 61801
Dr. Clare Hasler is the Executive Director of Functional Foods for Health
(FFH), a joint program of the University of Illinois at Chicago and the
University of Illinois at Urbana-Champaign, dedicated to the improvement of
human health through multi-disciplinary research, education and
communication focused on the identification of safe and efficacious foods
and other physiologically active natural products which may reduce chronic
disease risk or promote optimal health. Her research has dealt with the
health benefits obtained from consumption of soy protein products. Dr.
Hasler was a recipient of the 1997 Illinois Soybean Association's Friend of
Dr. Patricia Murphy*
Professor, Food Science and Human Nutrition
Iowa State University, 2312 Food Science Building, Ames, Iowa 50011-1061
Dr. Patricia Murphy has been studying and testing isoflavones for nearly 20
years and has been in the forefront of understanding the role isoflavones
have in human health. She is the developer of the U.S. Department of
Agriculture and Iowa State University Isoflavone Database, an authoritative
database of the isoflavone content of human foods which will help
scientists pinpoint which estrogen-like compounds -- isoflavones -- in soy
foods may be responsible for a lower risk of cancer, especially breast
cancer. A recipient of the Iowa State Board of Regents Faculty Excellence
Dr. Stephen Barnes*
Professor, Department of Biochemistry and Pharmacology
Department of Pharmacology, University of Alabama at Birmingham
Hall, Rm G010 UAB Station
Birmingham, Alabama 35294
Dr. Barnes is a recognized expert in the field of isoflavone analyticals
and the role these compounds play in preventing cancer. Trained in London,
England, he joined the Mayo Clinic in Rochester, Minnesota in 1975. He has
been at the University of Alabama-Birmingham since 1977 and is a Professor
in the Departments of Pharmacology & Toxicology and Biochemistry &
Molecular Genetics. He is also the Director of the Comprehensive Cancer
Center Mass Spectrometry Shared Facility.
Dr. Pam White* Department of Food Science
Human Nutrition Iowa State University
Ames, Iowa Phone 515-294-9688 Fax 515-294-8181
Dr. Pam White is a leading researcher in the area of the functional
properties of foods, including soybean, corn and oats. Dr. White is former
chair of the Department of Food Science at Iowa State University.
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