Development of food frequency questionnaire and database for assessing soy isoflavone intake in the Chinese population

An increasing number of studies has documented the effects of soy intake on the prevention of chronic diseases. The current study was conducted to develop a cultural-specific food frequency questionnaire and database for quantifying phytoestrogen exposure among the Chinese population in Hong Kong. Additionally, dietary information gathered through 24-hour dietary recalls was used to examine the patterns and determinants of soy consumption in this population.;The study subjects were midlife Chinese women (aged 50-61 years) recruited from an ongoing cohort study on osteoporosis. Participants were asked to complete two soy food frequency questionnaires (SFFQ) one-year apart; and provide 23 records of 24-hour dietary recalls (DR) during that period.;The isoflavone content in forty-nine composite samples of food items included in the SFFQ was analyzed by reverse phase high-performance liquid chromatography (HPLC) method. All soy products contained isoflavones ranging from one to 80 mg aglucon equivalents/100g wet weight. Results of the dietary assessment validation study further demonstrated that the SFFQ has moderate reproducibility with an intraclass correlation coefficient of 0.68, and an acceptable level of validity with a Pearson correlation coefficient of 0.53. Nonetheless, the Bland-Altman analysis suggested the differences between the two intake methods are proportional to their averages, and a bias might possibly exist among the Cantonese dialect group with an above-median dietary soy intake.;Over 3200 DR were successfully obtained from 141 subjects. The overall median daily intake of total isoflavones was 6.3 mg (interquartile range: 3.7 to 10.7 mg). The top five food sources contributed to 46% of the total soy isoflavone intake among the participants. Soy consumption was associated nonlinearly with age. Other factors associated with lower soy isoflavone intakes included being Cantonese and having poor self-rated health.;The findings from this dissertation will form the basis for future research on assessing the relationship between dietary soy isoflavones and their health effects in the Hong Kong Chinese population, in particular for midlife women.