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Assessing phytoestrogen exposure in
epidemiologic studies: development of a database (United States).
Cancer Causes Control 2000 Apr;11(4):289-98
Horn-Ross PL, Barnes S, Lee M, Coward L, Mandel JE, Koo J, John EM, Smith M.
Northern California Cancer Center, Union City 94587, USA. phornros@nccc.org
BACKGROUND AND OBJECTIVE: Phytoestrogens (weak estrogens found in plants or
derived from plant precursors by human metabolism) have been hypothesized to
reduce the risk of a number of cancers. However, epidemiologic studies
addressing this issue are hampered by the lack of a comprehensive phytoestrogen
database for quantifying exposure. The purpose of this research was to develop
such a database for use with food-frequency questionnaires in large
epidemiologic studies. METHODS: The database is based on consumption patterns
derived from semistructured interviews with 118 African-American, Latina, and
white women residing in California's San Francisco Bay Area. HPLC-mass
spectrometry was used to determine the content of seven specific phytoestrogenic
compounds (i.e. the isoflavones: genistein, daidzein, biochanin A, and
formononetin; the coumestan: coumestrol; and the plant lignans: matairesinol and
secoisolariciresinol) in each of 112 food items/groups. RESULTS: Traditional
soy-based foods were found to contain high levels of genistein and daidzein, as
expected, as well as substantial amounts of coumestrol. A wide variety of
"hidden" sources of soy (that is, soy protein isolate, soy concentrate, or soy
flour added to foods) was observed. Several other foods (such as various types
of sprouts and dried fruits, garbanzo beans, asparagus, garlic, and licorice)
were also found to be substantial contributors of one or more of the
phytoestrogens analyzed. CONCLUSIONS: Databases, such as the one described here,
are important in assessing the relationship between phytoestrogen exposure and
cancer risk in epidemiologic studies. Agencies, such as the United States
Department of Agriculture (USDA), that routinely provide data on food
composition, on which epidemiologic investigations into dietary health effects
are based, should consider instituting programs for the analysis of
phytochemicals, including the phytoestrogens.
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