Soya food intake and risk of endometrial cancer among Chinese women in Shanghai: population based case-control study

Author: Wang Hong Xu, Wei Zheng, Yong Bing Xiang, Zhi Xian Ruan, Jia Rong Cheng, Qi Dai, Yu Tang Gao, Xiao Ou Shu.
Publication: British Medical Journal, 2004 May 29; 328(7451):1285.

The objective of this study was to investigate the association between soya food (a dietary source of isoflavones) intake and the risk of endometrial cancer. It is known that Asian women, who eat more soya products than Western women, have lower incidence of endometrial cancer.

For this study information was collected from 832 women (cases) in the Shangai area which were diagnosed with endometrial cancer and 846 women (controls) without diagnosed endometrial cancer. The information was collected through interviews and measurements (body weight, length, waist and hip circumferences. Dietary information was collected during the past five years. From this information the total quantities of soya isoflavones, soya proteins and soy fibres were calculated.

The researchers found that the intake of soya food, measured either as soya protein intake or as soya isoflavones intake, was inversely associated with the risk of endometrial cancer. This inverse relationship was more pronounced among women with a high body mass index and high waist to hip ratio. The finding that the effect of soya food consumption was the highest for women with a high body mass index or waist to hip ratio supports the theory that isoflavones exerts an anti-estrogenic effect in an estrogen rich environment. Women with endometrial cancer had lower intake of total soya food intake and soya isoflavones. The association of endometrial cancer and soya food intake was not influenced by the menopausal status. Isoflavones have been shown to act as weak estrogens. Isoflavones can alter the level of endogenous estrogen by binding with estrogen receptors. Isoflavones also interfere with steroid biosynthetic enzymes, increases the production of sex hormone binding globulin and increase the clearance of steroid from the circulation. The fibres in soy also seem to lower the estrogen levels in the blood.

The study concluded that the intake of soya foods is associated with a reduced risk of endometrial cancer.