Background
Experimental and epidemiologic studies suggest that soy may promote weight loss.
Aim of the study
The goal of this study was to examine the relation of soy intake with body weight over the lifespan of women with Caucasian,
Japanese, and Native Hawaiian ancestry.
Methods
We assessed the relation between lifetime soy consumption and body mass index (BMI) among 1,418 women in Hawaii. All subjects
reported anthropometric measures, regular diet, and soy intake throughout life. The lifetime soy questionnaire was completed
again by a subset of 356 women 5 years after study entry and the κ values indicated moderate agreement. We regressed soy intake
on BMI at study entry and at age 21 while controlling for confounding variables, computed least square means, and performed
trend tests.
Results
Higher soy consumption in adulthood was related to a lower BMI (P = 0.02). This association was only significant for Caucasian women and for postmenopausal subjects. The women in the highest
category also experienced a smaller annual weight change since age 21 (by 0.05 kg/year) than the low soy intake group (P = 0.02). We observed no association between early life soy intake and BMI. High vegetable consumption was significantly associated
with a higher soy intake among Caucasian women.
Conclusions
In this study, women consuming more soy during adulthood had a lower BMI, but the relation was primarily observed for Caucasian
and postmenopausal subjects. This indicates that the association may be due to other nutritional factors and behaviors common
in women with high soy intake.
Key words soy - body mass index - obesity - ethnicity - early life nutrition