Soy Isoflavones
Isoflavone articles from The Soy Connection newsletter for registered dietitians, selected physicians and family and consumer science professionals...
- Isoflavones: New Frontier In Nutrition
- Interest in Isoflavones Continues to Increase
- Soy Isoflavones, Estrogens and Growth Factor Signaling
- Absorption and Metabolism of Isoflavones
Additional isoflavone information..
- Isoflavone Concentration in Soyfoods
- Second International Symposium On The Role of Soy In Preventing and Treating Chronic Disease
- Soybean Isoflavones: Levels in Foods and Pharmacokinetics
- Metabolism of Isoflavononoids in Japanese Men
Isoflavones: New Frontier In Nutrition
By Anne Patterson, R.D.
f you have read any health and nutrition columns in consumer magazines, newspapers or the internet, you are aware of the terms isoflavone, phytoestrogen and phytochemical. At times it may seem a little confusing. Besides, aren't the nutrients we've known about for years adequate for our health and well-being?
No one questions the importance of protein, carbohydrates, fat, vitamins and minerals to our health; however, new frontiers in the field of nutrition will be explored as we learn more about specific phytochemicals such as isoflavones. Phytochemicals are non-nutritive, meaning they are neither vitamins nor minerals. There are many hundreds of these bioactive plant chemicals found in dietary sources of fruits, vegetables, legumes, whole grains, nuts, seeds, herbs and spices.
Isoflavones have received a great deal of research, especially for possible cancer and heart disease-preventive properties. To date, most of the research has been done in animals, cell culture and in vitro studies. Isoflavones are a type of phytoestrogen, compounds that have weak estrogenic activity. There are many types of phytoestrogens and not all are in edible plants. Isoflavones are found in chick peas and legumes. The legume, soy, has the most concentrated amount.
The following questions are commonly asked by consumers trying to learn more about isoflavones.
Q. Where are isoflavones found in the soybean?
A. The isoflavones seem to be concentrated in the soybean hypocotyl (the part of the seedling below the seed leaves) with low to moderate amounts in the cotyledon (first layer of leaves formed on seedling).
Q. Are there factors which make a difference in the amount and forms of isoflavones in the soybean?
A. Soybeans contain three types of isoflavones in four chemical structures. Exact chemical analysis done on a wide variety of soyfoods and ingredients has shown a great difference in amounts of the isoflavones as well as their chemical forms. The variety of soybean grown, growing conditions, location and crop year, can all make a difference in the amount of isoflavones in soybeans.
Q. What soyfoods have the greatest amount of isoflavones?
A. All the soyfoods in the following list are excellent sources of isoflavones, providing a range of 30 - 50 milligrams per serving.
- Roasted soy nuts (1 ounce)
- Soy flour (1/2 cup)
- Soy grits (1/4 cup)
- Textured soy protein (1/2 cup, cooked)
- Yellow, green vegetable or black soybeans (1/2 cup, cooked)
- Regular soymilk (1 cup)
- Tempeh (1/2 cup)
- Tofu (1/2 cup)
Q. Don't other soyfoods or soy ingredients contain isoflavones?
A. Yes, most do, just in significantly smaller quantities. For example, miso is a good source, but who eats a 1/2 cup of miso, since it is used as an ingredient? Soy hot dogs, soy burgers, soy cheeses, soy yogurts and soy isolate powder do contain isoflavones, but competition with other ingredients and processing all affect amounts of isoflavones. The best way to know is to call the consumer line on the package of food and ask them if they have analyzed for isoflavones. Soy oil doesn't contain isoflavones.
Q. Are isoflavones destroyed in the cooking process?
A. Isoflavones are fairly stable, so under normal home or institutional cooking methods they are not destroyed.
Q. How much isoflavones should one eat a day?
A. Optimal isoflavone intake to prevent or treat specific diseases is not known. At this time, overall health benefits of isoflavones as well as other phytochemicals are best met by eating a varied diet from all food groups, built upon a foundation of one serving of soyfood with plenty of whole grains, fruits, vegetables and other legumes each day.
(Anne Patterson is president of Nutrition Advantage, a food and nutrition consulting company specializing in food and nutrition communications, marketing, recipe development and project management. She is a soy nutrition specialist, a nationally known speaker, a media spokesperson, and one of the presenters at Soy Connection seminars held throughout the country. Her e-mail address is: agprd@aol.com
Reprinted with permission from The Soy Connection newsletter, Volume 6, No. 2, Spring 1998. More information about the newsletter can be obtained by writing to:
- Editor, The Soy Connection
- P.O. Box 237
- Jefferson City, MO 65102
Copyright 1998
Indiana Soybean Board
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