Urinary isoflavonoid excretion and soy consumption in three generations of Japanese women in Hawaii

Abstract

Objective: To explore soy intake and urinary isoflavonoid excretion within several generations of American-Japanese women based on the hypothesis that earlier generations excrete higher levels of urinary isoflavonoids, in particular the metabolite equol, than later generations. Subjects: A convenience sample of 43 women from 19 families aged 18-78 years, all of whom reported at least 50% Japanese ancestry. Interventions: Each woman collected overnight urine samples at baseline and after consuming one serving of soymilk, both samples were analyzed for the isoflavonoids daidzein, genistein and equol using liquid chromatography-mass spectrometry. Results: Median isoflavone intakes during the last year were 7.2 mg/day for the first generation, 7.3 mg/day for the second generation and 6.3 mg/day for the third generation (P ¼ 0.36). At baseline, the median isoflavonoid excretion for the first generation was nonsignificantly higher than for later generations (190, 86 and 42 nmol/h; P ¼ 0.20) but after intervention, the median urinary isoflavonoid excretion was very similar for the three groups: 2465, 1895 and 2775 nmol/h (P ¼ 0.70). Following intervention, a nonsignificantly higher proportion of older than younger women (53 vs 32 and 33%; P ¼ 0.41) excreted the metabolite equol. The respective median equol excretion rates by generation following intervention were 39.5, 4.2 and 3.5 nmol/h (P ¼ 0.04). Conclusions: This small investigation among three generations of Japanese-Americans detected a higher equol production among older women after a soy challenge, but no difference in the excretion of total isoflavonoids after a standardized dose of soymilk was observed.

Development of an Updated Phytoestrogen Database for Use With the SWAN Food Frequency Questionnaire: Intakes and Food Sources in a Community-Based, Multiethnic Cohort Study

“…al , similarly reported higher mean phytoestrogen intake in the former (19 mg/day) than the latter (12 mg/day) (69). Comparing across-studies, Japanese women’s intakes of isoflavones specifically also appear to be higher than those of Chinese women, but cross-study results must be interpreted with caution due to differences in dietary measurement methods (74, 75). …”

Plasma Profiling of Intact Isoflavone Metabolites by High-Performance Liquid Chromatography and Mass Spectrometric Identification of Flavone Glycosides Daidzin and Genistin in Human Plasma after Administration of Kinako

“…Isoflavones are metabolized and then excreted as glucuronide, sulfate, and sulfoglucuronide conjugates in human urine (Doerge et al, 2000;Shelnutt et al, 2002). The conjugated compounds are generally converted to free aglycones by selective enzymatic hydrolysis and then analyzed by HPLC (Morand et al, 2001) or LC-MS methods (Maskarinec et al, 2007) that require less sample preparation than gas chromatography or gas chromatography-MS methods (Adlercreutz et al, 1995;Heinonen et al, 2003). These methods, however, provide data only on total glucuronides, sulfates, and free aglycones.…”

Dietary isoflavones and bone mineral density during midlife and the menopausal transition

“…This potential explanation would need to be explored with a food-level, rather than isoflavone-level, analysis. The ability to metabolize isoflavones to active forms (e.g., equol and p-ethyl phenol), which characterizes roughly 30% of Whites and 50% of Asians, may also underlie differences in the biological effects of isoflavones [40–42]. However, we know of no data that support a higher rate of isoflavone metabolic capacity in Japanese compared to Chinese women.…”