Soya and isoflavone intakes associated with reduced risk of oesophageal cancer in north-west China.

OBJECTIVE To ascertain the association between soya consumption, isoflavone intakes and oesophageal cancer risk in remote north-west China, where the incidence of oesophageal cancer is known to be high. DESIGN Case-control study. Information on habitual consumption of soya foods and soya milk was obtained by personal interview. The intakes of isoflavones were then estimated using the US Department of Agriculture nutrient database. Logistic regression analyses were performed to assess the association between soya consumption, isoflavone intakes and oesophageal cancer risk. SETTING Urumqi and Shihezi, Xinjiang Uyghur Autonomous Region, China. SUBJECTS Participants were 359 incident oesophageal cancer patients and 380 hospital-based controls. RESULTS The oesophageal cancer patients consumed significantly less (P < 0·001) total soya foods (mean 57·2 (sd 119·0) g/d) and soya milk (mean 18·8 (sd 51·7) ml/d) than the controls (mean 93·3 (sd 121·5) g/d and mean 35·7 (sd 73·0) ml/d). Logistic regression analyses showed an inverse association between intake of soya products and the risk of oesophageal cancer. The adjusted odds were OR = 0·33 (95 % CI 0·22, 0·49) and OR = 0·48 (95 % CI 0·31, 0·74) for consuming at least 97 g of soya foods and 60 ml of soya milk daily (the highest tertiles of consumption), respectively, relative to the lowest tertiles of consumption. Similarly, inverse associations with apparent dose-response relationships were found between isoflavone intakes and oesophageal cancer risk. CONCLUSIONS Habitual consumption of soya products appears to be associated with reduced risk of oesophageal cancer in north-west China.