4. Discussion
within-women, breast cancer
BREAST CANCER
In a randomized controlled trial of 90 healthy peri- and postmenopausal Malaysian women, we found no statistically significant differences in annual MD change for women with or without the soy isoflavone intervention. However, we found that high soy isoflavone intake may benefit women who are perimenopausal or recently menopausal, where an annual decline of up to 6 cmWe demonstrated a possible modest association between regular soy isoflavone intake and MD change among Asian women. These observations were substantiated in within-women analysis prior to the intervention for a subset of 62 women for whom a pre-enrolment mammogram was available. Despite some inconsistencies in observational studies [The association between moderate soy isoflavone intake and MD in our study is consistent with the published literature among Asian women, where habitual intake of at least 10 mg/day of isoflavones or 10 g/day of soy foods was associated with 10–16% lower relative risk of breast cancer [Our findings are in contrast to previous clinical trials of predominantly Caucasian women, where intervention doses of up to 120 mg/day of soy isoflavones have yielded no significant impact on MD measures [Researchers have also suggested that the lack of effect seen in clinical trials of post-menopausal women [This is the first RCT to investigate the effect of soy isoflavones on breast cancer risk among Asian women living in Asia, where soy is commonly available and is already part of dietary intake. To our knowledge, we are also the first to show that a soy intervention may specifically benefit women during or soon after menopause, possibly coinciding with the lobular involution of the breasts. Further investigation of this hypothesis may provide insight into the biological mechanism of how soy isoflavones affect breast cancer risk. An important strength of this trial is that all mammograms were conducted on a single digital mammography unit, and mammograms for each woman was aligned prior to MD estimation, thereby ensuring a robust measurement of MD change for each woman.This trial had some limitations. First, we were only able to enroll 52% of our desired sample size, and therefore, this study is underpowered to detect any meaningful difference in MD change across study arms. Additionally, up to 23% of women were lost in follow up. Though the rate of loss is comparable to previously published dietary intervention studies [