Associations Between Soy, Diet, Reproductive Factors, and Mammographic Density in Singapore Chinese Women

Abstract

Although the evidence is not completely consistent, soy intake has been inversely associated with breast cancer risk, and the strongest results have been observed in certain Asian populations. To address this issue and to examine the association between mammographic density and reproductive factors in this population, we conducted a cross-sectional analysis of mammograms and validated food-frequency questionnaires from 380 Chinese women living in Singapore. Percent mammographic density, a biomarker for breast cancer risk, was assessed using a validated computer-assisted method. We used generalized linear models to estimate mean mammographic density by quartiles of soy intake and intake of other dietary factors while adjusting for potential confounders. Percent mammographic density was inversely associated with age, body mass index, parity, breastfeeding, and soy intake. The difference in mammographic density between the highest and lowest quartiles of soy intake was 4-5%; this difference was statistically significant for soy protein and soy isoflavone intake and is similar in magnitude to what has been reported in Western populations when women undergo menopause or commence hormone therapy. We found no evidence that high fiber, fruit, or vegetable intake has protective effects on mammographic density. Our results suggest that the effect of soy intake on percent mammographic density is moderate but possibly of clinical relevance.

Soy Protein Containing Isoflavones and Mammographic Density in a Randomized Controlled Trial in Postmenopausal Women

“…In contrast to the findings of randomized trials, most (12,(31)(32)(33) but not all (34) cross-sectional studies show that women with high habitual consumption of soy have lower mammographic density. This might suggest that the duration of the intervention in the trials was too short.…”

Epidemiology of soy exposures and breast cancer risk

“…In another cross-sectional study conducted in Hawaii, high soy intake was associated with lower mammographic density among Chinese and Japanese women in Hawaii but higher mammographic density in Caucasians and Hawaiians; none of the associations was statistically significant. Three intervention studies of 1 -2 years duration, conducted in mostly premenopausal or perimenopausal women, failed to note any effects of soy, given as soy foods, red clover isoflavones or isoflavone supplements, on mammographic density (for a review, see Messina et al, 2006;Ursin et al, 2006). Thus, the collective evidence based on circulating hormones and mammographic density does not show any strong or consistent oestrogenic or anti-oestrogenic effects of soy on the breast.…”

Breast Cancer Susceptibility Variants and Mammographic Density Phenotypes in Norwegian Postmenopausal Women

“…35,36). Parity and possibly early age at first full-term pregnancy are both associated with lower percent MD (37)(38)(39)(40)(41). BMI is strongly inversely associated with percent MD (42), and there is some evidence that physical activity (43) and possibly alcohol intake (44)(45)(46) are associated with MD phenotypes.…”