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Plant Estrogens Low in Older Women’s Diets

By Judy McBride
September 28, 2001

There is evidence that natural, estrogen-like compounds in soybeans and many other plant foods may reduce hot flashes and vaginal dryness and increase bone density in women after menopause. But a careful inspection of the diets of nearly 1,000 older women in Massachusetts found their average intake of these phytoestrogens to be less than one milligram (mg) daily.

That’s only 1 to 5 percent of the phytoestrogen intake reported for Asian populations. Soybeans and soy protein products like tofu are concentrated sources of phytoestrogens and are common in Asian diets. By contrast, foods common in Western diets are far lower in these compounds.

Studies suggest that body cells respond to plant estrogens as if they were weaker versions of the human hormone. So consuming more of these estrogen-mimicking compounds may help compensate for the loss of estrogen naturally as women age.

Researchers at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University in Boston collaborated on the study with colleagues at the University Medical Center Utrecht in The Netherlands, Boston University School of Medicine and the University of Helsinki and Folkhalsan Research Center in Finland.

They estimated intakes of the three classes of phytoestrogens--isoflavones, lignans and coumestans--from food frequency questionnaires filled out by 964 postmenopausal, Caucasian women participating in the Framingham (Mass.) Offspring Study.

In contrast to Asian populations, the U.S. women got the bulk of their phytoestrogens--nearly 0.6 mg--from fruit, such as berries, citrus, apples and melon, in the form of secoisolariciresinol. The compound is one of the lignans, which are most concentrated in flaxseed.

The better known isoflavones--genestein, daidzein and formononetin--provided about one-fourth of the phytoestrogens in the women’s diets. And these came mostly from beans and peas rather than from soy products, according to study leader Paul Jacques, who heads nutritional epidemiology research at the USDA center.

The third class of phytoestrogens, coumestans, were barely detectable in the women’s diets.

The Boston center is funded by the Agricultural Research Service, USDA’s chief scientific agency.