Miso Soup and Soy Isoflavones Reduce Breast Cancer Risk
Frequent consumption of miso soup and high dietary intake of isoflavones are both linked to lower breast cancer risk, according to a new study in the Journal of the National Cancer Institute (2003;95:906–13).
Soy is widely consumed in Asian countries and its popularity is growing in the West. A variety of soy foods is eaten in the Asian diet, including tofu, miso, soymilk, soy sauce, soy flour, green or dried soybeans, soybean sprouts, and a fermented soy food called natto. Soy is the most significant source of dietary isoflavones, compounds that affect the estrogen receptors of the body and may have anti-cancer properties. The incidence of breast cancer is low in Asian populations and a number of studies have examined the possible link between soy consumption and reduced risk of breast cancer. Some of these studies have found that high intake of soy is associated with lower risk of breast cancer but others have found no such association.
In the current study nearly 22,000 Japanese women who had visited public health centers in Japan and who filled out a questionnaire were observed over a ten-year period. One question they answered concerned their consumption of miso soup and another their consumption of other soy foods, such as tofu, natto, and soybeans. Almost 75% of the women reported eating miso soup daily, and of these 34% ate three or more cups of miso soup per day. More than 45% reported eating soy foods other than miso daily. Intake of isoflavones was calculated using the information about miso and other soy food consumption. Women who reported eating three or more cups of miso soup per day had a 40% lower risk of developing breast cancer than did women who reported eating less than one cup per day. This risk reduction was seen for both premenopausal and postmenopausal women. Women with the highest intakes of isoflavones (top quartile) had a 54% lower risk of developing breast cancer than did those in the lowest quartile; however, this risk reduction was more dramatic in postmenopausal women than in premenopausal women.
The results of this study show that a diet high in isoflavone-rich soy foods and particularly miso can be protective against breast cancer. This effect may not be seen in populations that do not eat large amounts of soy. The average intake of isoflavones among participants in the current study was calculated to be about 700 times higher than that of Caucasians in the United States. It would be useful for future studies to examine the effects of high intake of other specific soy foods on breast cancer risk.
Maureen Williams, ND, received her bachelor’s degree from the University of Pennsylvania and her Doctorate of Naturopathic Medicine from Bastyr University in Seattle, WA. She has a private practice in Quechee, Vermont, and does extensive work with traditional herbal medicine in Guatemala and Honduras. Dr. Williams is a regular contributor to Healthnotes Newswire.
Copyright © 2003 Healthnotes, Inc. All rights reserved. Republication or redistribution of the Healthnotes® content is expressly prohibited without the prior written consent of Healthnotes, Inc. Healthnotes Newswire is for educational or informational purposes only, and is not intended to diagnose or provide treatment for any condition. If you have any concerns about your own health, you should always consult with a healthcare professional. Healthnotes, Inc. shall not be liable for any errors or delays in the content, or for any actions taken in reliance thereon. Healthnotes and the Healthnotes logo are registered trademarks of Healthnotes, Inc.